Tektronix 434 Instruction Manual

EXT H O R IZ mode of operation. When the T IM E /D IV switch is set to EXT H O R IZ, the X signal is connected to the H orizontal A m p lifie r circu it via the EXT H O R IZ input connector on the instrum ent rear panel. The CRT circu it determines the CRT intensity by summing the signal inputs from the IN TE N S ITY control, Channel Switch circu it (chopped blanking), Sweep Genera­ to r (unblanking), and the Z A X IS input connector. The CRT circu it also contains the controls necessary fo r opera­ tio n o f the cathode-ray tube. Trace storage is accomplished by the Storage circuit. The Power Supply circu it provides all the voltages necessary fo r operation of this instrum ent. The C alibrator circu it provides a square-wave o u tput w ith accurate am pli­ tude and frequency which can be used to check the calibra­ tio n o f the instrum ent and the compensation of probes. C IR C U IT OPERATION General This section provides a detailed description o f the elec­ trical operation and relationship o f the circuits in the 434. The theory of operation fo r circuits unique to this instru­ ment is described in detail in this discussion. C ircuits w hich are com m only used in the electronics industry are not described in detail. If more inform ation is desired on these com m only used circuits, refer to the follow ing textbooks: T e ktro n ix C ircuit Concepts Books (order from your local T e ktro n ix Field O ffice or representative). C a th o d e -R a y Tubes, T ektronix Part No. 062- 0852-01. H orizontal A m p lifie r C ircuits, T e ktro n ix Part No. 062-1144-00. Oscilloscope Trigger C ircuits, T e ktro n ix Part No. 062-1056-00. Power Supply C ircuits, T e ktro n ix Part No. 062- 0888-01. S w eep G enerator Circuits, T e ktro n ix Part No. 062-1098-01. V e rtic a l A m p lifie r Circuits, T e ktro n ix Part No. 062-1145-00. P h illip C u tle r, "Sem iconductor C ircuit A nalysis", M cG raw -Hill, New Y ork, 1964. Lloyd P. Hunter (Ed.), "H andbook of Sem iconductor E lectronics", second edition, M cG raw-Hill, New Y ork, 1962. Jacob M illm an and Herbert Taub, "Pulse, D igital, and Switching W aveform s", M cG raw -Hill, New Y ork, 1965. The follow ing c ircu it analysis is w ritten around the detailed block diagrams which are given fo r each major circuit. These detailed block diagrams give the names of the individual stages w ith in the m ajor circuits and show how they are connected together to form the m ajor circuit. The block diagrams also show the inputs and outputs fo r each circu it and the relationship of the front-panel controls to the individual stages. The circu it diagrams from which the detailed block diagrams are derived are shown in the Diagrams section. C H AN N EL 1 INPUT AMP AND PREAMP General In p u t signals fo r vertical deflection on the CRT can be connected to the CH 1 connector. The Channel 1 Input A m p and Preamp circuits provide control of input coupling, vertical deflection factor, balance, vertical position, and vertical gain. A sample o f the Channel 1 input signal is also provided to the Trigger P ickoff and Generator circu it to provide internal triggering from the Channel 1 signal only. Fig. 3-2 shows a detailed block diagram of the Channel 1 Input Am p and Preamp circuits. A schematic o f these circuits is shown on diagram 1 at the rear of the manual. Input Coupling Input signals applied to the CH 1 connector can be AC- coupled, DC-coupled, or internally disconnected. When Input Coupling switch S8A is in the DC position, the input signal is coupled directly to the Input A ttenuator circuit. In the AC position, the input signal passes through capacitor C8. This capacitor prevents the DC com ponent o f the signal from passing to the am plifier. When the GND pushbutton is pressed in, switch S8B opens the signal path and the input to the am plifier is connected to ground. This provides a ground reference w ith o u t the need to disconnect the applied signal from the CH 1 input connector. Resistor R8 allows C8 to be precharged so the trace remains on screen when switched to AC coupling w ith a high DC level applied. Variable capacitor C9 adjusts the basic input tim e constant fo r a nominal value o f one megohm X 24 picofarads. Input A ttenuator The effective overall Channel 1 deflection fa cto r of the 434 is determined by the CH 1 V O LT S /D IV switch. In all positions of the CH 1 V O LT S /D IV switch above 5 m V, the basic deflection factor o f the Vertical D eflection System is 10 m illivolts per division of CRT deflection. T o increase this basic deflection factor to the values indicated by the V O LT S /D IV switch, precision attenuators are switched into the circuit. In the 1, 2, 5, and 10 mV positions, input attenuation is not used. Instead, the gain o f the Preamp 3-3

C irc u it D e s c rip tio n —4 3 4

C ircuit is changed to decrease the deflection factor (see Preamp C ircuit discussion). For the CH 1 V O LTS /D IV switch positions above 10 mV, the attenuators are switched into the circuit singly or in pairs to produce the vertical deflection factor indicated by th e V O L T S /D IV switch. These attenuators are frequency-compensated voltage dividers. In addition to providing constant attenuation at all frequencies w ithin the bandwidth of the instrum ent, the Input Attenuators are designed to maintain the same input RC characteristics (one megohm X 24 picofarads) fo r each setting of the CH 1 V O LTS /D IV switch. Each attenuator contains an adjustable series capacitor to provide correct attenuation at high- frequencies and an adjustable shunt capacitor to provide correct input capacitance. NOTE Each attenuator is a hybrid encapsulated assembly; therefore, replacement o f individual components is n o t possible. Should defects occur, the attenuator m ust be replaced as a unit. Scale-Factor Switching Circuit The vertical deflection factor of Channel 1 is indicated by back-lighting the appropriate figures im printed on the flange of the CH 1 V O LTS /D IV knob. When a X I probe is connected to the CH 1 input connector, the base of Q200 is connected to +15 volts through R200. Q200 is biased into saturation and conducts current through indicator DS20. DS20 indicates the correct deflection factors fo r X I probes. When Q200 conducts, the voltage level at its collector is very close to zero volts; therefore, there is insufficient bias at the base of Q202 to cause it to conduct, and X I 0 indi­ cator DS22 remains dark. When a X I 0 probe w ith a scale factor switching connector is attached to the CH 1 input connector, the base of Q200 is grounded. Q200 does not conduct, and its collector rises to approximately +15 volts. X I indicator DS20 is dark and Q202 is forward biased into conduction. Q202 conducts current through X10 indicator DS22, which now indicates the correct vertical deflection factor, includ­ ing the X I 0 attenuation ratio of the attached probe. Input Stage The Channel 1 signal from the Input A ttenuator is connected to the Input Stage through C121, R121, and R122. R120 provides the input resistance for this stage. R121 lim its the current drive to the gate of Q124A. Dual­ diode CR122 protects the circuit by clamping the gate of Q124A at about —15.5 or +15.5 volts if a high-amplitude signal is applied to the CH 1 connector. FET Q124B is a relatively constant current source fo r Q124A. and also provides temperature compensation of Q124A. R125 isolates the input of the Preamp Stage from the source of Q124A. Preamp Stage The Preamp Stage U210 is a multiple-stage integrated circuit amplifier. Adjusting the gain of this stage sets the overall gain fo r Channel 1. Basic gain of the am plifier is set by adjusting R244. VAR control R245 permits continu­ ously variable uncalibrated deflection factors between the calibrated settings of the V O LTS /D IV switch. R212 adjusts fo r no base line shift of the CRT display when rotating the VAR control. In the 1, 2, 5, and 10 mV positions of the V O LTS /D IV switch no attenuation is used in the Input A ttenuator stage. The correct vertical deflection factors are obtained by changing the gain of the Channel 1 Preamp Stage. This is accomplished by changing the value of the gain-setting resis­ tance connected between pins 7 and 8 of U210. The STEP ATTEN BAL screwdriver adjustment R22 located on the instrum ent fro n t panel adjusts fo r no baseline shift of a CRT display when switching between the 1, 2, 5, and 10 mV positions of the CH 1 V O LTS /D IV switch. Variable capacitors C217, C220, C223, C225, and C226 are compensation adjustments to provide optim um high- frequency response through the channel am plifier. A sample of the signal being amplified in Channel 1 is taken from pin 19 of U210 and connected to the Trigger Pickoff and Generator circuit to allow Channel 1 only triggering operation. Q255 and Q265 in the O utput A m plifier stage are connected as common-base amplifiers to provide low input impedance load for the Preamp Stage. They also provide isolation between the Preamp Stage and the Channel Switch circuitry. CHANNEL 2 INPUT AMP AND PREAMP General The Channel 2 Input Am p and Preamp circuits are basically the same as the Channel 1 Input Am p and Preamp circuits. Only the differences between the tw o circuits are described here. Portions of this circuit not described in the following description operate in the same manner as for the Channel 1 Input Am p and Preamp. Fig. 3-3 shows a detailed block diagram of the Channel 2 Input Amp and Preamp. A schematic of these circuits is shown on diagram 2 at the rear of this manual. Preamp Stage Basically the Channel 2 Preamp Stage operates as described fo r Channel 1. However, the Channel 2 Preamp 3-5

signal fo r triggering use. Also, IN VER T switch S414 has been added in the Channel 2 circuit. This switch allows the displayed signal from Channel 2 to be inverted. CHANNEL SWITCH General The Channel Switch circuit determines whether the CH 1 and/or CH 2 Vertical Preamp output signal is connected to the Vertical O utput A m plifier circuit. In the A LT and CHOP modes of operation, both channels are alternately displayed on a shared-time basis. Fig. 3-4 shows a detailed block diagram of the Channel Switch circuit. A schematic of this circuit is shown on diagram 3 at the rear o f this manual. Diode Gate The Diode Gates, consisting of four diodes each, can be thought of as switches which allow either o f the Vertical Preamp output signals to be coupled to the Delay-Line Driver stage. CR404, CR405, CR406, and CR408 control the Channel 1 signal output, and CR410, CR411, CR412, and CR414 control the Channel 2 signal output. These diodes are in turn controlled by the Switching M ultivibrator fo r dual-trace displays, or by the Vertical Mode switch for single-trace displays. CH 1. In the CH 1 mode of operation, —15 volts is applied to the junction of CR411-CR412 in the Channel 2 Diode Gate through Vertical Mode switch S45A, R427, and CR433 (see simplified diagram in Fig. 3-5). This forward biases CR411-CR412 and reverse biases CR410-CR414, since the input to the Delay-Line Driver Stage is at about +6 volts. CR410-CR414 block the Channel 2 signal so it cannot pass to the Delay-Line Driver stage. A t the same time in the Channel 1 Diode Gate, CR405-CR406 are connected to +15 volts through R420. CR405-CR406 are held reverse biased, while CR404-CR408 are forward biased. Therefore, the Channel 1 signal can pass to the Delay-Line Driver stage. CH 2. In the CH 2 mode of operation, the above con­ ditions are reversed. CR405-CR406 are connected to —15 volts through S45E, R429, and CR431, and CR411-CR412 are connected to +15 volts through R425 (see simplified diagram in Fig. 3-6). The Channel 1 Diode Gate blocks the signal, and the Channel 2 Diode Gate allows it to pass. Switching M ultivibrator A LT . In this mode o f operation, the Switching M u lti­ vibrator operates as a bistable m ultivibrator. —15 volts is connected to the em itter of Q435 (Alternate Trace Switching A m plifier stage) through R437. Q435 is forward biased and supplies current to the “ o n " transistor in the C o m p o site 3-6 Fig. 3-4. Channel S w itch detailed block diagram .

Channel 1 D iode Gate C U R R E N T PATH R E VE R S E-BIA S E D D IO D E S V ertical signal to D elay-Line D river Stage Fig. 3-5. E ffe c t o f D iode Gates on signal path (sim p lifie d pa th). C o n d itio n s shown fo r CH 1 m ode o f operation. Switching M ultivibrator stage through R435 and CR428 or CR426. For example, if Q420 is conducting, current is supplied to Q420 through CR426. The current flow through collector resistor R420 drops the CR405-CR406 cathode level negative w ith respect to the cathodes of CR404 & CR408, so the Channel 1 Diode Gate is blocked, as fo r Channel 2 only operation. The signal passes through the Channel 2 Diode Gate to the Delay-Line Driver. The alternate-trace sync pulse is applied to Q435 through C430 at the end of each sweep. This differentiated negative-going sync pulse mom entarily interrupts the current through Q435, and both Q420 and Q425 are turned o ff. When Q435 turns on again after the alternate-trace sync pulse, the charge on C425 determines whether Q420 or Q425 conducts. For example, when Q420 is conducting, C425 is charged more positively on the CR426 side to the 3-7

C hannel 1 D io d e G ate C U R R E N T P A T H R E V E R S E -B IA S E D D IO D E S V e rtic a l signal to D e la y -L in e D riv e r Stage Fig. 3-6. E ffe c t o f D io d e G ates on signal p a th (s im p lifie d p a th ). C o n d itio n s sh o w n fo r C H 2 m o de o f o p e ra tio n . em itte r level o f Q 420, and more negatively (tow ard the collector level o f Q 435 through R 428, C R432 and R432) on the C R 428 side. T his charge is stored w hile Q 435 is o ff, and holds the e m itte r o f Q 425 more negative than the em itte r o f Q 420. When both Q 420 and Q 425 are o ff the voltage at th e ir bases becomes approxim ately equal. When Q 435 comes back on, the transistor w ith the m ost negative em itte r w ill start conducting firs t, w ith the resulting negative m ovem ent at its collector holding the other tran­ sistor o ff. The co n d ition s described previously are reversed; now the Channel 2 D iode Gate is reverse biased, and the Channel 1 signal passes through the Channel 1 D iode Gate. CHOP. In the CHOP mode o f operation, the S w itching M u ltiv ib ra to r Stage free runs as an astable m u ltiv ib ra to r at 3-8

about a 100 kHz rate. The emitters of Q420 and Q425 are connected to —15 volts through R428, R426, the primary of T435, and R438. A t the time of turn-on, one of the transistors begins to conduct; for example, Q420. The negative level at the collector of Q420 forward biases C R 405-C R 406 and back biases CR404 and CR408, preventing the Channel 1 signal from reaching the Delay- Line Driver stage. Meanwhile, the Channel 2 Diode Gate passes the Channel 2 signal to the Delay-Line Driver stage. The frequency-determining components in the CHOP mode are C425-R419-R426-R428. Switching action occurs as follows: when Q420 is on, C425 attempts to charge to — 15 volts through R428. The em itter of Q425 slowly goes toward —15 volts as C425 charges. The base of Q425 is held at a negative point determined by the voltage divider R423-R421 between —15 volts and the collector voltage of Q420. When the em itter voltage of Q425 reaches a level slightly more negative than its base, Q425 conducts. Its collector level goes negative and pulls the base of Q420 negative through divider R422-R424 to cut Q420 off. This switches the Diode Gate stage to connect the opposite half to the Delay-Line Driver stage. Again C425 begins to charge toward —15 volts, but this time through R426. The emitter of Q420 slowly goes negative as C425 charges, until Q420 turns on. Q425 is shut o ff and the cycle begins again. Diodes CR426 and CR428 are prevented from conducting by CR432 and R432, so they are effectively removed from the circuit in the CHOP mode. The Chopped Blanking A m plifier stage, Q440, provides an output pulse to the Z Axis A m plifier circuit which blanks out the transitions between the Channel 1 and the Channel 2 traces. When the Switching M ultivibrator stage changes states, the voltage across T435 m om entarily increases. A negative pulse is applied to the base of Q440 to turn it o ff. The w idth of the pulse at the base of Q440 is determined by R436 and C436. Q440 is quickly driven into cu to ff and the positive-going output pulse, which is coincident w ith trace switching, is connected to the Z Axis A m plifier circuit through CR440 and R445. ADD. In the ADD mode of operation, the Diode Gate stage allows both signals to pass to the Delay-Line Driver stage. The Diode Gates are both held on by —15 volts applied to their cathodes through R450 and R452. Since both signals are applied to the Delay-Line Driver stage, the output signal is the algebraic sum of the signals on both Channels 1 and 2. Delay-Line Driver O utput o f the Diode Gate stage is applied to the Delay- Line Driver stage Q454 and Q470. Q454 and Q470 are connected as feedback amplifiers w ith C456-R456-R457 and C472-R472-R474 providing feedback from the collec­ tor to the base of the respective transistor. A sample of the signal in the collector circuit of Q470 is used for triggering in the COMP mode of trigger operation. Switch S479 connects capacitor C479 between the output signal lines to reduce the upper —3 dB bandwidth lim it of the Vertical A m p lifie r system to a p p ro xim a te ly 5 megahertz. C 4 6 0 -R 4 6 0 and C461-R461 provide high frequency compensation of the Delay Line term ination. The output of the Delay-Line Driver stage is connected to the Vertical O utput A m plifier through the Delay Line. VER TIC AL OUTPUT AM PLIFIER General The Vertical O utput A m plifier circuit provides the final am plification for the vertical deflection signal. This circuit includes the Delay Line and the BEAM FINDER push­ button. The BEAM FINDER pushbutton compresses an overscanned display to w ithin the viewing area when pressed. Fig. 3-7 shows a detailed block diagram of the Vertical O utput A m plifier circuit. A schematic of this circuit is shown on diagram 4 at the rear of this manual. Delay Line Delay Line DL500 provides approximately 140 nano­ seconds delay for the vertical signal to allow the Sweep V ertica l D eflectio n Signal to C R T V ertica l D eflectio n Plates 3-9 Fig. 3-7. V e rtica l O u tp u t A m p lifie r detailed block diagram.

vertical signal reaches the vertical deflection plates of the CRT. This allows the instrum ent to display the leading edge of the signal originating the trigger pulse when using internal triggering. Input A m plifier Q 5 0 5 and Q545 are connected as common-base amplifiers to provide a low input impedance to properly terminate the Delay Line. It also provides isolation between the Delay Line and the follow ing stages. Q520 and Q550 lim it the maximum dynamic swing of the am plifier by turning on and conducting when excessive amounts of signal are present at the am plifier input. When closed, the BEAM FINDER switch S50 forward biases CR521 and CR551, thereby setting a more positive level at the bases of Q520 and Q550. This more positive level makes Q520 and Q550 conduct on smaller-than-normal overdrive signals, causing the overall dynamic swing of the Vertical O utput A m plifier to be lim ited w ithin the CRT graticule area. Q515 and Q555 are em itter followers to provide low o u t­ put impedance. O utput A m plifier Q525 and Q565 comprise an emitter-coupled push-pull am plifier that drives the output power amplifiers Q530 and Q580. R568, R571, R572 and R574 set the gain of the stage by controlling the signal degeneration between the emitters of Q525 and Q565. R572 is a therm istor which reduces in resistance w ith increases in ambient temperature. This increases the gain of the stage, to counteract the reduc­ tion in overall am plifier gain that occurs when the ambient temperature increases. Variable capacitor C572 and the series RC network C570 and R570 provide high-frequency compensation to optim ize am plifier frequency response. L533 and L584 are high-frequency peaking adjustments to provide additional am plifier compensation. TRIGGER PICKOFF AND GENERATOR General The Trigger Pickoff circuit selects and amplifies the internal trigger signal to the level necessary to drive the Trigger Generator circuit. Input signal for the Trigger Pick­ o ff circuit is either a sample of the signal applied to Channel 1, or a sample of the composite vertical signal from the Channel Switch circuit. The Trigger Generator circuit produces trigger pulses to start the Sweep Generator circuit. These trigger pulses are derived either from the internal trigger signal from the vertical deflection system, an external signal connected to the EXT TRIG input connector, or a sample of the line voltage applied to the instrum ent. Controls are provided in this circuit to select trigger level, slope, coupling, and source. Fig. 3-8 shows a detailed block diagram of the Trigger Pickoff & Generator circuit. A schematic of this circuit is shown on diagram 5 at the back of this manual. Trigger Pickoff Diode Gate. The Diode Gates, consisting of tw o diodes each, can be thought o f as switches which allow either of the tw o internal trigger signals to be coupled to the Trigger P ickoff A m plifier. CR280 and CR285 control the Channel 1 signal, and CR270 and CR275 control the composite signal. These diodes are in turn controlled by the TRIGGER SOURCE switches. For CH 1 trigger operation, +15 volts is applied to the anode of CR270 through COMP Source switch S72B. R270 is forward biased and pulls the collector circuit of Q280 positive, which back biases and turns o ff CR275. CR285 remains forward biased, and couples the CH 1 trigger signal to the base of Q275. In the COMP mode of trigger opera­ tion, + 15 volts is applied to the anode of CR280 through COMP Source switch S72B and R282. CR280 is now forward biased, pulling the cathode of CR280 positive, which back biases and turns o ff CR285. CR275 remains forward biased and couples the amplified COMP trigger signal present in the collector circuit of Q280 to the base of Q275. R274 and R284 set the DC level at the collector of Q275 to zero volts fo r no-signal, zero-volt input level conditions. Q275 and Q278 comprise an emitter-coupled compara­ to r am plifier. Q275 by itself is a feedback am plifier, w ith R285 providing feedback from the collector to the base of Q275. The DC level at the base of Q278 determines the DC level at the base of Q275. Trigger Source The TRIGGER SOURCE switches S72A and S72B select the source of the trigger signal. Four trigger sources are available: CH 1, COMP, external, and line. EXT ATTEN switch S70 provides 13 times attenuation for the external trigger signal. The internal trigger signals (CH 1 and COMP) are obtained from the Trigger Pickoff circuit discussed above. The line trigger signal is obtained from the secondary of transformer T i l 15 in the Power Supply Primary circuit. This sample of the line frequency, about .7 volt RMS, is coupled to the Trigger Generator circuit in the LINE mode of operation, The TRIGGER COUPLING switches should not be in the LF REJ mode of operation when using this trigger source, as the signal w ill be blocked by the LF reject circuit. 3-10

Fig. 3-8. T rig g e r P ic k o ff a nd G e n e ra to r d e ta ile d b lo c k dia g ra m . External trigger signals applied to the EXT TRIG input connector can be used to trigger the Sweep Generator in the EXT TR 1G mode of operation. Input resistance at DC is about one megohm paralleled by about 100 picofarads (about 70 picofarads when EXT ATTEN switch S70 is in the 1:10 position). Setting the EXT ATTEN switch to the 1:10 position attenuates the input signal by a factor of 10 to provide more LEVEL control range, while maintaining the one megohm input resistance characteristic. Trigger Coupling The TRIGGER COUPLING switches S74, S75A, and S75B offer a means of accepting or rejecting certain components of the trigger signal. In the AC and LF REJ mode of trigger coupling, the DC component of the trigger signal is blocked by coupling capacitor C72 or C74. Frequency components below about 60 hertz are attenu­ ated when using AC coupling and below about 50 kilohertz w hen using LF REJ coupling. The higher-frequency components of the trigger signal are passed w ithout attenuation. In the HF REJ mode of trigger coupling, the trigger signal is DC coupled to the input if the AC and LF REJ p u s h b u tto n s are not also depressed. High-frequency components of the trigger signal (above about 50 kilohertz) are attenuated, while the lower-frequency components are passed w ith o u t attenuation. The DC mode of trigger coupling passes all signals from DC to 25 megahertz. Input Source Follower The Input Source Follower, Q605A, provides a high input impedance for the trigger signal. It also provides isolation between the Trigger Generator circuit and the trigger signal source. Diode CR603 protects Q605A if an excessive negative input voltage is applied to the EXT TRIG input connector. The output at the anode o f VR605 is connected to emitter follow er stage Q610. Q6058 is a relatively constant current source for Q605A, and provides temperature compensation of Q605A. Slope Comparator U650D and U650E are connected as an emitter-coupled difference am plifier (comparator) to provide selection of the slope and level at which the sweep is triggered. The reference voltage for the comparator is provided by the LEVEL control R60B and the Trigger Level Centering 3-11

adjustment R629. The Trigger Level Centering adjustment sets the level at the base of U650E so the display is correctly triggered when the LEVEL control is centered. The LEVEL control varies the base level of U650E to select the point on the trigger signal where triggering occurs. Diodes CR615 and CR616 prevent overdrive occurring in the Slope Comparator. Q618 is a relatively constant current source fo r U650D and U650E. The slope of the input signal which triggers the Sweep Generator is determined by the SLOPE switch S60. When the SLOPE switch is set to +, +5 volts is connected to the base of Q635 through R635 and to the anode of CR634. See Fig. 3-9. This forward biases CR634, which turns on and pulls the cathode of CR634 positive also. A t the same tim e the base-emitter junction of Q635 is zero biased, which turns o ff Q635. W ith Q635 turned o ff, its collector falls to a level of about +2 volts set by the voltage divider R637-R638. This back biases CR635, and the trigger signal in the collector circuit of U650D is allowed to pass to the Trigger TD CR644. The trigger signal in the collector circuit of U650E is conducted by CR634 and blocked from reaching the Trigger TD by back-biased diode CR632. The trigger signal in the collector circuit of U650D is amplified and inverted w ith respect to the input trigger signal. Since the output pulse from the Trigger Generator is derived from the negative-going portion of the signal applied to the Trigger TD, the sweep is triggered on the positive-going slope of the input trigger signal. When the SLOPE switch is set to —, conditions are reversed. The base of Q635 is returned to ground through R634 and R635. See Fig. 3-10. This back biases CR634 and forward biases the base-emitter junction of Q635 suf­ ficiently to drive Q635 into saturation. The collector of Q635 rises to w ithin about 0.2 volt o f the em itter, which forward biases CR635. Now CR630 is back-biased and CR632 is forward biased, allowing the trigger signal present in the collector circuit of U650E to be applied to the Trigger TD. The trigger signal in the collector circuit of U650E is in phase w ith respect to the input trigger signal, so the sweep is triggered on the negative-going slope of the input trigger signal. Trigger TD The Trigger TD stage shapes the output of the Slope Comparator to provide a trigger pulse w ith a fast leading edge. Tunnel diode CR644 is quiescently biased so it is on and in its low-voltage stage. The current from one of the transistors in the Slope Comparator stage is diverted through the Trigger TD stage. As the current increases due to a change in the trigger signal, tunnel diode CR644 switches to its high-voltage state. The tunnel diode remains 3-12 Fig. 3-9. Trigger signal path fo r positive-slope triggering (sim p lified Trigger G enerator diagram ).

Fig. 3-10. Trigger signal path fo r negative-slope triggering (sim p lifie d Trigger G enerator diagram ). in this condition until the current from the Slope Compara­ tor stage decreases due to a change in the trigger signal applied to the input. Then the current through CR644 decreases and it reverts to its low-voltage state. SWEEP GENERATOR General The Sweep Generator circuit produces a sawtooth voltage which is amplified by the Horizontal A m plifier circuit to provide horizontal sweep deflection on the CRT. This output signal is generated on command (trigger pulse) from the Trigger Generator circuit. The Sweep Generator also produces an unblanking gate to unblank the CRT during sweep tim e and an alternate trace sync gate to switch vertical channels during sweep retrace time. Fig. 3-1 1 shows a detailed block diagram of the Sweep Generator circuit. A schematic of this circuit is shown on diagram 6 at the back of this manual. The Sweep MODE switch allows three modes of opera­ tion. In the NORM mode, a sweep is produced only when a trigger pulse is received from the Trigger Generator circuit. Operation in the AUTO mode is much the same as NORM, except that a free-running trace is displayed in the absence of an adequate trigger signal. In the SINGLE SWEEP mode, operation is also similar to NORM except that the sweep is not recurrent. The follow ing circuit description is given w ith the sweep MODE switch set to NORM. Differences in operation fo r the other tw o modes are discussed later. Normal Sweep Mode Operation Sweep Gate. The negative-going trigger pulse generated in the Trigger Generator circuit is applied to the Sweep G ate stage th ro u g h inverting am plifier Q645 and C663-R663. CR678 is quiescently biased on in its low- voltage state. When the positive-going trigger pulse is applied to the anode of CR678, the current through the tunnel diode increases and it rapidly switches to its high- voltage state, where it remains until reset by the Sweep Reset M ultivibrator stage at the end of the sweep. The positive-going level at the anode of CR678 is connected to the base of U680A through R680. U680A is turned on and its collector goes negative. This negative-going step is connected to the base of U680B through C686-R686. U680B is turned o ff and its collector, goes positive. This positive-going step is connected to the base of the Sweep Gate A m plifier. Sweep Gate A m plifier. The Sweep Gate A m plifier U680C is an em itter follow er quiescently conducting 3-13

CO © C ircu it D escription—434

current through R742, R796, R794, R692, and R690. When sweep triggering occurs, the positive-going excursion at the base of U680C is present in the em itter circuit and is applied to pin 1 of the Sawtooth Sweep Generator U700 and the base of U680D. Gate O utput Comparator. The positive-going signal at the base of U680D turns U680D on, and turns U680E off. The negative-going excursion at the collector of U680D is applied to the em itter of H oldoff Driver U760C, and is also coupled to the Z-Axis circuit through R790, CR794, and CR795 to unblank the CRT during sweep time. A t the same time that the collector of U680D is going negative, the collector of U680E is going positive. This positive-going voltage is applied to the base of the Pulse A m plifier U760E and a positive-going Alternate Trace Sync Pulse is coupled from the em itter to the Channel Switch circuit while a negative going Enhance Pulse is coupled from the collector to the Storage circuit. H o ld o ff D riv e r. The negative-going signal at the collector of U680D when the sweep begins is connected to the H oldoff Capacitor through U760C. This negative-going signal discharges the H oldoff Capacitor completely at the start of each sweep to provide accurate sweep holdoff time. CR785 clampsThe collector of U760C so it does not go more negative than about —0.5 volt. Sawtooth Sweep Generator. The basic sweep generator is a M iller Integrator circuit. When pin 1 of U700 is positive, the tim ing capacitor, Cy, begins to charge through the tim ing resistor, Ry. The tim ing resistor and capacitor are selected by the T IM E /D IV switch S700 to provide the various sweep rates listed on the fro n t panel. Diagram 8 shows a complete diagram of the T IM E /D IV switch. The Sweep Cal adjustment R727 allows calibration of this circuit fo r accurate sweep tim ing. The Variable T IM E /D IV control R799 provides continuously variable uncalibrated sweep rates by varying the charge rate of the tim ing capacitor. R703 is an Offset adjustment to adjust the quiescent DC level at pin 9 of U700 to zero volts. This reduces tim ing current errors between positions of the T IM E /D IV switch. The output sawtooth voltage signal at pin 8 of U700 is applied to the Horizontal A m plifier input. Voltage divider R705-R706 determines the amplitude of the sawtooth ramp. When the ramp reaches this predetermined level, a reset pulse is generated at pin 4 o f U700. This reset pulse is applied to the base of U760A in the Sweep Reset M u lti­ vibrator and to the base of U680E in the Gate O utput Comparator. Sweep Reset M ultivibrator. Quiescently, U760A is turned o ff and U760B is turned on. The sweep reset pulse (a narrow, positive-going, rectangular pulse) is applied to the base of U760A through R700 and CR710. U760A is turned on and its collector goes negative. This negative movement is coupled to the base of U760B and turns it o ff, causing its collector to go positive. The positive movement at the collector of U760B is coupled to the base of U650C which, prior to this, had been turned o ff. The increase in forward bias of the base-emitter junction of U650C drives it into saturation. The collector of U650C moves negative until it is only a few tenths of a volt more positive than the grounded emitter. The negative movement of the collector of U650C is coupled to the anode of Sweep Gating Tunnel Diode CR678 through R678, causing CR678 to switch from its high-voltage state to a low-voltage state where it is conducting almost no current. As long as U650C is turned on, CR678 is prevented from switching to its high voltage state. H oldoff Em itter Follower. When the sweep reset pulse causes U760A and U760B to reverse states, the pulse also causes U680E and U680D in the Gate O utput Comparator to switch states. The reset pulse turns on U680E which causes U680D to turn o ff. The positive movement at the collector of U680D when it turns o ff causes U760C to turn o ff and the H oldoff Capacitor, Ch o » starts to charge positive through R778 and R60A. This positive movement is coupled through H oldoff Em itter Follower U760D and em itter resistor R774 to the anode of diode CR765. When sufficient forward bias is achieved, CR765 w ill turn on and couple the positive-going movement to the base of U760B in the Sweep Reset M ultivibrator, causing U760B to turn on and U760A to turn off. The negative movement at the collector of U760B turns U650C o ff and CR678 conducts current in its low-voltage state, ready to receive the next trigger pulse. R60A varies the charge rate of the H oldoff Capacitor to provide a stable display at fast sweep rates. This change in holdoff allows sweep synchronization for less display jitte r at the faster sweep rates, and has very little effect at slow sweep rates. R60A is ganged w ith the TRIGGER LEVEL control and is adjusted by rotating the LE VEL knob. The H oldoff Capacitor is changed by the T IM E /D IV switch for the various sweep rates to provide the correct holdoff time. Auto Sweep Mode Operation Operation of the Sweep Generator circuit in the AUTO mode is the same as fo r the NORM mode just described when an adequate trigger pulse is present. However, when an adequate trigger pulse is not present, a free-running reference trace is produced in the AUTO mode. This occurs as follows: A uto M ultivibrator. U650A and U650B form a mono­ stable m ultivibrator. Quiescently w ith no trigger pulses being generated by the Trigger Generator circuit, U650B is conducting and U650A is biased o ff by only about 150 m illivolts. W ith U650A not conducting, its collector moves 3-15

c o n d u c t. Q660 conducts its current through R646, C663-R663, and Sweep Gating Tunnel Diode CR678. The added current through tunnel diode CR678 autom atically switches it to its high-voltage state at the end of the sweep hoidoff period. The result is that the Sweep Generator circuit is autom atically retriggered at the end of each hold- o ff period, and a free-running sweep is produced. Since the sweep free-runs at the sweep rate of the Sweep Generator, a bright reference trace is produced even at fast sweep rates. When trigger pulses are being produced by the Trigger Generator circuit, positive-going pulses are coupled to the base o f U650A by transformer T645. These positive pulses turn on U650A, which causes U650B to turn o ff. The collector of U65QA goes negative and the collector of U650B goes positive, which combines to turn o ff CR660 and Q660. When U650A turned on and its collector went negative, capacitor C650 discharged very rapidly. If the m ultivibrator does not receive another trigger pulse, C650 w ill recharge to approximately +15 volts in about 115 m illi­ seconds. The auto gate level at the collector of transistor Q660 w ill be negative when the Trigger Generator circuit is producing trigger pulses, and positive when the Trigger Generator circuit is not producing trigger pulses. In both the NORM and SINGLE SWEEP modes of operation, —15 volts is applied to the anode of CR660 through R660 to back bias CR660 and prevent Q660 from conducting. Single Sweep Mode Operation General. Operation of the Sweep Generator in the SINGLE SWEEP mode of operation is similar to operation in the other modes. However, after one sweep has been produced, the Sweep Reset M ultivibrator stage does not reset. A ll succeeding trigger pulses are locked out until the RESET button is pushed. In the SINGLE SWEEP mode of operation, —15 volts is applied to the top of READY light DS65 and to the em itter of CR770. CR770 is forward biased and holds CR765 back biased to prevent the Sweep Reset M ultivibrator from resetting at the end o f the sweep hoidoff time. Single-Sweep Reset. The Single Sweep Reset circuit produces a pulse to reset the Sweep Reset M ultivibrator stage so another sweep can be produced in the SINGLE SWEEP mode of operation. A fter a sweep has been pro­ duced in the SINGLE SWEEP mode, U760A is on and U760B is off. Pressing the RESET pushbutton applies +15 volts to the voltage divider made up of R784, R783, and R782. C782 capactively couples a positive-going spike to the anode o f CR765. CR765 becomes forward biased and turns on, coupling the positive-going spike to the base of U760B. U760B now turns on and U760A turns off. When U760B turns on, its collector goes negative, which turns Q665 o ff and also turns U650C o ff, allowing the Sweep Gating Tunnel Diode CR678 to accept the next trigger pulse. When Q665 turns o ff, its collector goes positive, allow ­ ing sufficient voltage to be impressed across READY light DS65 to turn the READY light on. This indicates that the Sweep Generator is ready to produce a sweep upon receipt of the next trigger pulse. When the next trigger pulse is received, the collector of U680B in the Sweep Gating M u lti­ vibrator w ill go positive and turn on Q 665.The collector of Q665 w ill go negative, causing the READY LIG H T to turn off. HO RIZO NTAL AM PLIFIER General The Horizontal A m plifier circuit provides the output signal to the CRT horizontal deflection plates. The signal applied to the input of the Horizontal A m plifier is deter­ mined by the T IM E /D IV switch. The signal can be a saw­ tooth waveform generated internally w ithin the instrument, or some external signal applied to the EXT HORIZ input connector located on the instrum ent rear panel. The H ori­ zontal A m plifier circuit also contains the horizontal magnifier circuit and the horizontal positioning network. Fig. 3-12 shows a detailed block diagram of the Horizontal A m plifier circuit. A schematic of this circuit is shown on diagram 7 at the rear of this manual. Input Paraphase Am plifier The input signal for the Horizontal A m plifier is selected by the T IM E /D IV switch, S700A. In all positions of the switch except EXT H O R IZ, the sawtooth from the Sweep Generator circuit is connected to the base of Input A m plifier Q825A. In the EXT HORIZ position of the switch, the signal applied to the base of Q825A is obtained from the EXT HORIZ input connector. Q825A and Q825B comprise an emitter-coupled para­ phase am plifier. This stage converts the single-ended input signal to a push-pull signal necessary to drive the horizontal deflection plates of the CRT. R816, R817, R826 and R827 control the em itter degeneration between Q825A and Q825B to set the gain of the stage. The adjustment of R817 determines overall horizontal am plifier gain. Q818 is a constant current source fo r Q825A and Q825B. Horizontal positioning is provided by the POSITION control (R55A- R55B) connected to the base of Q825B. This control is a dual-range control to provide a com bination of coarse and fine adjustment in a single control. When the control is rotated, fine control R55B provides positioning fo r a range of about 0.3 major division fo r a normal (unmagnified) display. Then after the fine range is exceeded, the coarse control R55A provides rapid positioning of the trace. R816, R817, R826 and R827 control the em itter degenera­ tion between Q825A and Q825B to set the gain of the @ 3-16

T IM E /D IV S700A i I I E xternal 1 W —i

zontal am plifier gain. Pressing the LOCATE button applies — 15 volts to the base of Q825B through R95 and R811. This provides a small amount of positioning of the display in the direction of the non-store pre-view area to aid in locating display prior to storing a single-sweep. The output signals from the collectors of Q825A and Q825B are applied to the bases of em itter followers Q830A and Q830B respectively. Signal Lim iting Push-Pull A m plifier Q835 and Q836 form a push-pull am plifier stage w ith Q835A and Q836A comprising a cascade am plifier in one side and Q835B and Q836B a cascade am plifier in the other side. Sweep magnification is accomplished by m odifying the gain setting resistance between the emitters of Q835A and Q835B. CR835 and CR865 lim it the difference in signal amplitude between the bases of em itter followers Q836A and Q836B. This prevents amplifier over-drive when the sweep is magnified or positioned to one extreme or the other. CR836 and CR866 provide additional overdrive protection. Q861 is a relatively constant current source for Q835 and Q836. When the BEAM FINDER push-button is pushed the current through Q861 is reduced by approxi­ mately tw o milliamperes. This reduces the dynamic range of the signal lim iting push-pull am plifier stage, thereby lim iting the trace to w ithin the CRT graticule area. The M agnifier Registration adjustment R868 balances the quiescent DC current to the bases of Q870 and Q880 so a centerscreen display does not change position when the sweep is magnified. O utput Am plifier The push-pull output of the Signal Lim iting Push-Pull A m plifier stage is connected to the O utput A m plifier through CR870 and CR880. Each half of the O utput A m plifier can be considered as a single-ended feedback am plifier which amplifies the signal current at the input to produce a voltage output to drive the horizontal deflection plates of the CRT. The amplifiers have a low input impedance and require very little voltage change at the input to produce the desired output change. Q895 is a relatively constant voltage source. The base of Q895 is biased to set the em itter at approximately +5 volts and the anode of CR898 at approximately +6.5 volts. This sets the base of Q880 and the base of Q870 very near the same quiescent DC level. CR870 and CR880 become back biased and are turned o ff when overdrive in the positive direction occurs at their cathodes. Transistors Q870 and Q880 are inverting amplifiers whose collector signals drive the emitters of complementary amplifiers Q874-Q877 and Q884-Q887 respectively. The output signal from complementary am plifier Q874-Q877 drives the left horizontal deflection plate of the CRT, and th e o u tp u t signal fro m com plem entary am plifier Q884-Q887 drives the right horizontal deflection plate. C871 and C881 adjust the transient response of the am plifier so it has good linearity at fast sweep rates. POWER SUPPLY PRIMARY General The Power Supply Primary circuit provides controlled drive to the primary of power transformer T1085 to achieve more efficient generation of secondary voltages. This circuit also contains the circuitry necessary to regulate the secondary voltages against change due to variations in input line voltage or frequency, or changes in power supply load. Figure 3-13 shows a detailed block diagram of the Power Supply Primary circuit. A schematic of this circuit is shown on diagram 9 at the rear of this manual. Line Input Power is applied to this circuit through Line Fuse F I 0 0 0 , R1002, Thermal C utout S1002, Line Filter FL1010, and POWER switch S1Q10. Resistor R1002 limits the amplitude of surge currents at instrument turn-on. Thermal cutout S1002 provides thermal protection for the instrument. If the internal temperature of the instrument exceeds a safe operating level, S1002 opens to interrupt the applied power. When the temperature returns to a safe level, S I002 closes to re-apply the power. The Line Filter made up of C1004, C l006, L I004, R1004, and T1004 is designed prim arily to suppress the 25-kilohertz interference originating w ithin the power supply. L I 004 provides differential and common-mode inductance; T1004 provides additional common-mode inductance. Common-mode filtering is provided by C l005 and C l006 along w ith the common-mode inductance of T 1 0 0 4 . R1004 provides common-mode damping for C 1004-C1006-T1004. When the POWER switch S1010 is closed, line voltage is applied to the primary of transformer T1115 and to the full-wave bridge-rectifier C R 1016. T 1 115 provides a sample of the AC line-voltage to the Trigger Generator circuit for operation in the LINE triggering mode. CR1016 rectifies the AC line voltage into a DC voltage to be used in the Power Supply Primary circuit. Cl 016 provides a measure of filtering to the remaining AC component. R1016 discharges C1016 when instrum ent power is turned o ff. Transformer T1036 provides additional 25-kilohertz filtering. 3-18

CD T i l 15 To Power Supply Secondary Circuits Circuit Description—434

The rectified DC power is applied in itia lly to the Power Supply Primary C ircuit by the S tart C ircuit made up of D S 1020, DS1024, Q1025, Q 1030, Q1032 and their associated circu itry. DS1020, DS1024, C1024, R1020, and R1024 form a relaxation oscillator w ith a very low repe­ titio n rate (waveform period of approxim ately 5 seconds). When DS1024 is on and DS1020 is o ff, the base-emitter junction of Q1025 is forw ard biased, causing Q1025 to conduct. The collector c ircu it o f Q1025 moves negative (very near the floating com m on potential) causing the base- em itter junctions of Q1030 and Q1032 and the diode CR1032 to be back-biased, preventing them from con­ ducting. When DS1020 is on and DS1024 is o ff, conditions are reversed. Q1025 is o ff and its collector rises to an approxi­ mately +51 vo lt level (w ith respect to the floating com m on) determined by zener diode V R 1025. Q1030, Q 1032, and CR1032 conduct, causing the junction of CR1032 and R1034 to rise to an approxim ately +50 volt level. This establishes a tem porary V cc voltage supply for the T urn On and Turn O ff circuits in lieu of the normal V cc voltage supplied by one w inding of T1085 and half-wave rectifier CR1085. Normal circu it operation now takes place and a sufficiently positive V cc voltage is generated to back-bias and prevent CR1032 from conducting. Current Driver The C urrent Driver stage, Q1080, controls the current conducted through the prim ary w inding of Power Trans­ form er T1085. Q1080 is in turn controlled by signal pulses from the T urn On and Turn O ff circuits. Quiescently Q1080 is biased o ff, and m ust receive a positive-going pulse at its base from the Turn On circu it in order to conduct current through T 1085. The T urn O ff circu it m onitors the current conducted through T 1085 and generates a tu rn -o ff pulse when a preset maxim um level o f current is reached. Zener diodes VR 1084 and VR1085 prevent the collector of Q1080 from going more than 250 volts more positive that the reference level at the anode o f V R 1085. This reference level w ill be dependent upon the value o f line voltage applied to the instrum ent. This clamping action prevents exceeding the em itter to collector breakdown voltage rating o f Q1080 during transform er flyback tim e when Q1080 is turned o ff, and also aids in regulation o f the negative high voltage power supply. Turn On C ircuit The Turn On circu it generates the pulse required to cause Q1080 to turn on and conduct current through the prim ary of T1085. W ith an adequate V cc voltage supply at the em itter o f Q1045, Q1045 w ill be biased in to saturation. The collector of Q1045 w ill be w ith in about 0.2 vo lt o f the em itter. C l046 starts to charge toward this positive level through R1046. When the charge on C l046 reaches a level about 0.6 vo lt more positive than the level at the gate of Q1050, Q1050 w ill turn on and start to conduct current to discharge C l046 and, at the same tim e, forw ard bias the base-emitter junction of Q1064. When the current flow through Q1050 falls below the level necessary to keep Q1050 on, Q1050 w ill turn o ff and C l 046 w ill start to charge again. When Q1050 turns on, Q1064, w hich is quiescently biased o ff, starts to conduct current through the parallel com bination of R1064 and the prim ary w inding of trans­ form er T1064. T1064 couples a positive-going movement to the em itter o f Q1065. This positive movement is coupled back to the base of Q1064 through CR1060, R1060, and R1062, which reinforces the turn-on bias of Q1064. The positive movement at the em itter of Q1065 turns it on, which causes a positive pulse to be coupled to the base of Q1080 through CR1068 and R1068. Q1080 now turns on and starts to conduct current through the prim ary w inding o f T 1085. Turn O ff C ircuit To prevent Q1080 from conducting excessive amounts o f current, the Turn O ff circu it m onitors the am ount of current flow ing in the prim ary w inding o f T 1085, and generates a tu rn -o ff pulse when a preset current level is reached. The secondary w inding o f T1080 develops a voltage across R1075 and C urrent Sense A djustm ent R1074. When this voltage level becomes about 0.6 volt more positive than the voltage level at the gate of Q1075, Q1075 turns on and conducts current through R1076, CR1075, and the secondary w inding o f T1080. The resulting positive movement at the cathode o f Q1075 is coupled through C l076 to the base of Q1078. Q1078 now turns on and conducts current through the parallel com bination of R1078 and the prim ary w inding of T 1078. The negative movement at the collector o f Q1078 is coupled through R1071, C l071, and CR1070 to the base of Q1064 in the Turn On circu it to interrupt the turn-on process w hile the Turn O ff circu it is tryin g to stop conduc­ tio n through Q1080. Transform er T1078 couples a negative-going pulse through CR1078 and CR1079 to the base of Q1080. The negative-going pulse at the base of Q1080 is of sufficient am plitude to cause reverse current to flo w through the base-emitter junction of Q1080, and insure rapid tu rn -o ff. CR1081 and CR1082 clamp the base of Q1080 at an approxim ate —4 v o lt level during trans­ form er flyback. Damping C ircuit When the Current Driver stage Q1080 is turned o ff and stops conducting current through T1085, the magnetic field in T1085 collapses very rapidly. A fte r this flyback tim e, high am plitude ringing is generated in T1085. Q1090, © 3-20

damper circu it designed to suppress this ringing. When the Turn On c irc u it generates the turn-on pulse fo r Q1080, the negative movement at the collector o f Q1064 is coupled through C1093, CR1092, and R1095 to the base o f Q 1091. The resultant narrow negative-going pulse at the base o f Q1091 starts to turn o ff Q1091 and Q1094. The positive m ovem ent at the collector o f Q1065 is also coupled back to the Damping C ircuit and applied to the base of Q1090 through CR1090 and R1090. Q1090 turns o ff, and its collector goes negative, w hich serves to hold Q1091 and Q1094 o ff. When Q1080 is turned o ff, its collector steps positive to a level determined by the clamping action of VR1085 and V R 1084. T1085 transform s this into a negative movement at the cathode of CR1091 to hold Q1091 and Q1094 o ff. The negative movement at the collector o f Q1065 is applied to the base of Q1090 through CR1090 and R 1090, turning Q1090 on. A b o u t five to ten microseconds after the tu rn ­ o ff time of Q1080, flyback ends, ringing occurs in T 1085 and CR1091 turns o ff. Q1091 and Q1094 are turned on by Q1090 and conduct very heavily through the full-wave bridge rectifier CR1096-CR 1099 and one w inding of T 1085 to reduce the am plitude o f the ringing. The damping tran­ sistors Q1091 and Q1094 thus conduct only during the tim e flyback ringing is occurring. C1095, CR1095, and the transform er w inding connected to the cathode of CR1095 form a half-wave rectifier power supply generating approxim ately —5 volts to be used in the Damping C ircuit. Regulator C ircuit The Regulator C ircuit holds the outputs of the Power Supply relatively constant despite variations in input line voltage, line frequency, and load demand. Regulation is accomplished by varying the tim e interval between current pulses conducted in the prim ary w inding o f T1085 by Q1080. C l 136 and R1132 comprise a tim ing c irc u it to deter­ mine the interval between the regulating pulses. C l 136 charges tow ard the voltage level at pin 6 of U1130 through R1132 and CR1132. When the charge on C l 136 reaches a level about 0.6 vo lt more positive than the voltage level at the gate of Q1138, Q1138 conducts current to discharge C l 136 and, at the same tim e, forw ard bias the base-emitter ju nction of Q1150, When the current flo w through Q1138 falls below the level necessary to keep Q1138 on, Q1138 w ill turn o ff and C l 136 w ill start to charge again. When Q1138 turns on, Q 1150, w hich is quiescently biased o ff, turns on and conducts a current pulse through C ircuit D escription—434 the prim ary w inding of T1150. T1150 couples a negative- going pulse to the base of Q1040 through CR1040. Q1040 turns on and its collector moves positive to tu rn on Q1Q50, w hich starts the sequence o f events necessary to generate a turn-on pulse fo r Q1080. The tim e interval between pulses generated in the Regu­ lator circu it is altered by m onitoring variations in the —15 volts supply. For example, when heavy load demands are being made on the —15 vo lt supply it attem pts to go posi­ tive. This positive movement results in a positive movement in the voltage level at pin 6 of U 1 130. A more positive level at pin 6 of U 1 130 shortens the am ount o f tim e required by C l 136 to charge to the level at which Q 1138 turns on. This results in more turn-on pulses being generated fo r Q1080, thereby increasing the am ount o f energy transferred through T1085 per u n it o f tim e, POWER SUPPLY SECONDARY General The Power Supply Secondary circu it rectifies the AC voltages present in the secondary windings of Power Trans­ form er T1085 to provide the necessary DC supply voltages to the instrum ent circu itry. A schematic of this circu it is shown on diagram 10 at the rear o f this manual. Rectifier Circuits A ll o f the rectifier circuits in the Power Supply Second­ ary are half-wave rectifiers. LI 102, LII04, and LI 106 provide added filte rin g fo r the +115 vo lt, +15 vo lt, and the —15 vo lt supplies respectively. T1100 provides common-mode in d u c ta n c e to suppress the 25-kilohertz interference originating in the power supply circuit. The High-Voltage supply is a series of ten half-wave rectifier power supplies. T otal o u tp u t voltage o f the supply is approxim ately 4.1 kilovolts fo r use in the CRT circuit. CR1199 provides DC filam ent voltage to the CRT. CRT CIRCU IT General The CRT C ircuit contains the control c irc u itry necessary fo r operation of the cathode-ray tube (CRT). Fig. 3-14 shows a detailed block diagram o f the CRT circuit. A schematic of this circu it is shown on diagram 11 at the rear o f this manual. Unblanking A m plifier The U nblanking A m p lifie r circu it controls the CRT intensity level from several inputs. The effect of these input signals is to either increase or decrease the trace intensity, or to com pletely blank portions of the display. A portion o f integrated circu it U 940A is used to convert the voltage 3-21

GO rb N> Regulation Signal to Negative High Voltage Power Supply +15 V *■? R80 - 1 5 V Intensity Limiting fro m TIME/DIV switch 25 kHz from Power Supply Negative High Voltage Circuit Description—434

signals present at the am plifier inputs into current varia­ tions to drive the output portion of the Unblanking A m plifier. CRT intensity variations are accomplished in the follow ing manner. When a sweep starts, the DC level present at pin 2 of U940A steps negative, resulting in a reduced current flow from pin 9 of U940A. This reduction in current increases the forward bias on Q954 and reduces the forward bias on Q955. Q954 conducts harder, resulting in a positive move­ ment at the em itter of Q954. This positive movement is coupled through C942 to the em itter of Q940 and starts a positive movement at the collector of Q940. A t the same tim e that this is occurring, Q955 is decreasing its conduc­ tion through R955 and Q950, which causes a positive movement to occur at the collector of Q950, which reinforces and sustains the positive movement started by Q940. A t the end of the sweep, conditions are reversed. The DC level at pin 2 of U940A steps positive, causing increased current flo w from pin 9 of U940A and the collec­ tors of Q940 and Q950 move negative. The variations in DC level at the collectors of Q940 and Q950 are connected to the DC Restorer circuit. To reduce the possibility of burning the CRT phosphor, the em itter voltage of Q940 is changed by the T IM E /D IV switch, S700A. In the 50 m s/DIV position and up, the T IM E /D IV switch applies +115 volts to the junction of R943 and VR944. In all switch positions below 50 m s/DIV, + 115 volts is no longer connected to the junction of R943 and VR944. Instead, the em itter o f Q940 is returned to + 115 volts through R942, R943, and VR944. This produces a less positive level at the em itter of Q940 to lim it the collector level of Q940 and Q950 which protects the CRT phosphor in these switch positions. DC Restorer Circuit Q924 and Q925 form a complementary am plifier, each side of which conducts on a half cycle of the waveform coupled through T920 from the secondary of the power supply transformer. The voltage on the collector of Q924 is determined by the output of the Unblanking A m plifier. On the positive half cycle, Q924 saturates and the common emitters seek the Q924 collector voltage. On the negative half cycle, Q925 saturates and the common emitters go to ground potential. C924, C925, CR926, CR928, and R928 form a DC restorer network. A ll DC voltage levels in this circuit are referenced to the negative high-voltage potential. The voltage difference across R928 approximately equals the voltage swing present on the common emitters of Q924 and Q925. The upper end of R928 is more positive than the lower end, but negative w ith respect to the CRT cathode. Varying the drive signal to the Unblanking A m plifier changes the voltage level at the am plifier output, which in turn varies the amplitude of the voltage swing on the common emitters of Q924 and 0925, thereby resulting in changes to the CRT bias. CR924 and CR925 lim it the positive excursion that can occur at the collector of Q924 and the common emitters o f Q924 and Q925 respectively. CRT Grid Bias adjustment R980 determines the level of the range of adjustment of the INTENSITY control. CR935 provides protection to the CRT if the grid tries to rise more positive than the cathode. High Voltage Regulator Feedback from the high-voltage circuit is connected to pin 20 of integrated circuit U940B. A ny change in this sample of the high-voltage level produces an in-phase error signal at pin 17 of U940B which is amplified and inverted through Q989, Q990, and G995. Regulation occurs as follows: If the negative high-voltage level attempts to go positive (less negative), a sample of this positive-going voltage is applied to pin 20 of U940B. This results in a positive-going error signal at pin 17 of U940B which is applied to the base o f Q989 through CR982. Q989 amplifies and inverts this error signal, which receives further am plification through Q990 and Q995. The resulting negative movement at the collector of Q995 is applied to the positive pole of the minus high-voltage supply, and is of sufficient amplitude to maintain the output level of the supply. VR985 through VR990 prevent more than 900 volts from appearing across Q989, Q990, and Q995 to prevent exceeding the maximum voltage rating of these devices in the event of circuit failure. CR983 prevents the base of Q989 from going more negative than about —0.5 volt. R963 adjust the negative high-voltage power supply for the proper output voltage. CRT Control Circuits Focus of the CRT display is determined by the Focus control R82B. This control is part of voltage divider R962C, R968, R82B, R83, R962D, R962E between the negative high-voltage and ground. Therefore, the voltage applied to the focus grid is more positive (less negative) than the voltage on either the control grid or cathode. R968 sets the range of adjustment of the Focus control. The Focus control is ganged w ith the front-panel INTEN­ SITY control, and is autom atically adjusted when changes are made in the IN TEN SITY setting. The ASTIG adjust­ ment R85, which is also adjusted to obtain a well-defined display, varies the positive level on the astigmatism grid. Geometry adjustment R967 varies the positive level on the horizontal deflection plate shield to control the overall geometry of the display. The TRACE ROTATION adjust­ ment R80 controls the current through L100, which varies the magnetic field around the CRT to horizontally align the CRT trace. 3-23

C A LIB R A TO R General The C alibrator circu it produces a square-wave o u tp u t w ith accurate am plitude and frequency. This o u tp u t is available as a square-wave voltage at the PROBE C AL 0.6 V 1 kHz connector. Fig. 3-15 shows a detailed block diagram of the C alibrator circu it. A schematic of this c irc u it is shown on diagram 11 at the back of this manual. M ultivibrator Q905 and Q910 along w ith their associated circu itry comprise an astable m u ltivib ra to r. Basic frequency o f the m ultivib ra to r is determined by the RC com bination of R906, R910, and C906. R904 provides a measure o f adjust­ m ent o f C alibrator frequency. In the C alibrator M ultivib ra to r, Q905 and Q910 are never both conducting at the same tim e. Assume fo r purposes o f explanation th a t Q905 has just turned o ff and Q910 has turned on. When Q905 turns o ff, its collector moves positive, w hich also pulls the base of Q910 positive. This positive movement turns Q910 on and charges C906 positive. Im m ediately, the em itter of Q905 begins to discharge toward —15 volts. When the Q905 side of C906 has discharged sufficiently to forw ard bias the base-emitter junction of Q905, Q905 turns on and its collector moves negative. The negative movement at the collector of Q905 turns o ff Q910. Now the em itter circu it of Q910 begins to discharge tow ard —15 volts. When the Q910 side of C906 has discharged sufficiently to forward bias the base-emitter ju nction of Q910, Q910 turns on. A t the tim e Q910 turns on, a positive movement is coupled from the em itter of Q910 to the em itter of Q905 by C906. This positive move­ ment at the em itter o f Q905 reduces the current flo w through Q905, causing a reinforcing positive movement at Fig. 3-15. C a lib ra to r de ta ile d b lo c k diagram . the base of Q910. Q905 rapidly turns o ff as Q910 turns on. The square wave signal at the collector of Q910 is connec­ ted to the O utput A m p lifie r. O utput A m p lifie r The o u tp u t signal from the C alibrator M ultivibrator stage overdrives Q915 to produce an accurate square wave at the output. When the base of Q915 goes positive, Q905 is cu t o ff and the o u tp u t signal drops negative to ground. When the base goes negative, Q915 is driven in to saturation and the collector of Q 915 rises positive to about +15 volts. The o u tp u t voltage is connected from the voltage divider R915-R916-R918 to the PROBE C AL 0.6 V 1 kHz connec­ tor. R915 adjusts the overall ratio of the voltage divider to provide an accurate o u tp u t voltage am plitude. STORAGE C IR C U IT The Storage C ircuit provides the voltage levels necessary to operate the flood guns, collim ation electrodes and target backplates. The storage cathode-ray tube has tw o targets fo r split-screen operation; therefore, tw o identical erase generators are provided, each consisting of an Erase M u lti­ vibrator and a Target C ontrol A m p lifie r. These circuits produce an erase waveform w hich w ill erase w ritte n in fo r­ m ation. A d d itio n a l c ircu itry includes the Enhance Genera­ to r, w hich perm its very fast single sweeps to be stored, and the IN TEG R A TE sw itch, w hich perm its a stored image o f a number of repetitive sweeps, each of which w ould be too fast to store alone as a single sweep event. Fig. 3-16 shows a detailed block diagram of the Storage C ircuit. Storage Tube Basic Operating Principles The CRT used in the 434 is a direct-view storage cathode ray tube w ith a split screen viewing area that perm its each half to be individually operated fo r stored displays. Storage, which is the retention on the CRT screen of a displayed event, is based on a secondary emission principle. A stream of prim ary electrons strikes an insulated target surface w ith sufficient energy to dislodge secondary electrons. As the potential increases, each prim ary electron dislodges more than one secondary electron, resulting in the target material charging positive. The target approaches the backpiate potential, yielding a higher energy flood electron and resulting in lig h t output. The storage cathode ray tube contains special storage elements in addition to the conventional w ritin g gun elements. The operating mode of the tube depends prim arily on the voltages applied to these storage elec­ trodes. W ith one condition o f applied potentials, the storage screen or target backpiate operates in the ready-to- w rite state; then, when it is bombarded w ith high energy w riting beam current, the bombarded portion shifts to the stored mode to store a w ritte n display. W ith a d iffe re n t set 3-24

ERASE 1 S90A Erase M ultivibrator Q1210 Q1216 Cl 200 OFF Divider Network R1229 OFF Enhance Trigger Pulse From __ Sweep C ircuit ON STORE S90B ENHAN C E S90C Enhance M ultivibrator Q1245 Q1246 OFF Q 6 ON R90 ENHANCE LEVEL . R92 E N H A N C E --------------------------------------- » S92C OFF , ON CO NJ cn R1252< ERASE S92A R1250 Erase M ultivibrator Q1260 Q1266 C l 250 Divider Network 'X STORE S92B R1279 . C ircuit Description—434

ventional m ode, sim ilar to a conventional cathode ray tube. Circuit Description—434 The storage screens contain a special coated surface w hich continues to em it light when bombarded by the flood gun electrons, provided the surface has been w ritte n by the w ritin g gun beam and shifted to the stored state. The tw o targets are electrically isolated from each other, which allows simultaneous presentations of stored inform a­ tio n on one half and non-store (conventional) inform ation on the other half of the viewing area. Fig. 3-17 illustrates the basic construction of the 434 storage tube. The flood guns are low-energy electron guns which direct a large area flo w , or cones, of electrons toward the entire screen. The coliim ation electrodes shape the flo o d spray fo r uniform coverage of the storage targets. The operating level of the tube is the potential difference between the target backplates and the flood gun cathodes. The coliim ation electrodes have no effect on the bom ­ barding energy o f the flood gun electrons. In the store mode ready-to-write state, the insulator sur­ face o f the target tends to charge down to a potential lower than the backplate potential, and toward the potential of the flood gun cathode. This is due to flood gun current from the insulator surface. The potential to which the target charges is called its rest potential. This potential is such that the flood gun electron landing energy is not enough to illum inate the phosphor in the target. The target is now ready to w rite. See Fig. 3-18. In the w ritin g process, the target is scanned by the w ritin g gun electrons. These high energy electrons increase the target secondary emission over the area they scan, so th a t the ratio of secondary current to prim ary current becomes greater than one. (This is shown in Fig. 3-18 as the first crossover point.) When this ratio exceeds one, th a t part of the bombarded surface shifts to a new stable state. W riting has been accomplished and this segment o f the target is now stored. In the w ritte n state, the potential difference between the flood gun cathode and target becomes greater and the flood gun electrons now have a landing energy th a t is sufficient to provide a visual display. This visual display w ill continue as long as the flood gun beam covers the target. A t high sweep rates, the w ritin g beam current is not adequate to bring the p o rtion of the target scanned above the crossover p o in t; therefore, the flood gun electrons when landing on the bombarded area w ill remove the charge developed by the w ritin g gun electrons, and the target w ill discharge to its initial ready-to-write state w ith o u t being 3-26 Fig. 3-17. P ic to ria l diagram o f storage tu b e C R T .

backplate voltage is gradually returned, the target is charged to the rest potential and the target is in the ready-to-write state. For a comprehensive study of storage tube operating principles, a T ektronix C ircuit Concepts paperback book entitled "Storage Cathode-Ray Tubes and C ircuits" is available through your local T ektronix, Inc., Field Office or representative. Tektronix Stock No. 062-0861-00. Flood Guns and Collimation Electrodes Two low-energy electron guns, or flood guns, are used in the 434. The cathodes are returned to —75 volts through INTEG RATE switch S94 and R94. R 1298 and VR 1298 set the level of the flood-gun control grid at approximately + 140 volts. Fig. 3-18. Secondary emission curve. w ritten. Thus, complete w riting is a function of w riting beam current density. When the stored display is no longer desired, the in fo r­ mation is erased by a waveform as illustrated in Fig. 3-19. A positive-going pulse is first applied, to raise the backplate voltage above the w riting threshold and w rite the entire target area w ith flood gun electrons. Next, the backplate voltage is pulled well below the rest potential, then as the Fig. 3-19. T yp ica l erase cycle w aveform . The collim ation electrodes serve as an electrostatic lens to distribute the flood gun electrons uniform ly over the storage target, and they have no effect on the landing energy of the electrons. R1293 and R1925 determine the voltage levels of CE1 and CE2 through em itter followers Q1294 and Q1296 respectively. R1292 is an additional CRT Geometry adjustment. Target Control Am plifiers The Target Control Am plifiers are incorporated to main­ tain a high degree of control of the upper and lower storage backplate voltages. These are em itter-follower feedback amplifiers consisting of Q1230, Q1232, and Q1235 for the upper target backplate and Q1280, Q1282, and Q1285 for the lower target backplate. A bootstrapping circuit is provided for each Target Control A m plifier to maintain transistor operating voltage during the positive-going por­ tion of the erase waveform (fade positive). The boot­ strapping circuits w ill be described in fu ll detail in the Erase Generator discussion. A separate STORE switch is provided for each Target Control A m plifier, S90B (upper) and S92B (lower), allow ­ ing the target backplates to be operated individually. In the STORE mode, that is, when the STORE buttons are pushed in and the CRT is shifted to the ready-to-write state, the backplate voltages are adjusted individually by the Store Level controls, R1226 and R1276. These adjustments set the value of current to the feedback am plifier null points (Q1230 and Q1280 emitters), in the non-store, or conven­ tional mode, the backplate voltages are established by adjustment of the Non-Store Level adjustments R1224 and R 1274. 3-27

generators; however, the circuit numbers used are those o f the upper circuit. In order to erase the stored display, a fade-positive pulse is first applied to the storage target backplate. This increases the potential difference between the flood gun cathodes and target backplate, raising the operating level above the upper w riting lim it and w riting the entire target area w ith flood gun electrons. Next, the backplate voltage is pulled negative, well below the retention theshold. Then as the backplate is gradually returned, the target is charged to the rest potential and returned to the ready-to-write state. The follow ing paragraphs describe how the erase waveform is generated. The Erase M ultivibrator is composed o f Q1210, Q1216, and their associated circuitry. This is a monostable m u lti­ vibrator w ith Q1210 quiescently saturated and Q1216 biased o ff. The collector of Q1216 is clamped slightly above ground by the conduction of CR1219. C1214 is charged to the voltage difference between the junction of R 1 214-R 1212 and the collector level of Q1216. When the ERASE button is pushed, the contacts of S90A are closed, grounding R1203. This produces a negative-going step which turns Q1210 o ff and Q1216 on. The collector of Q1216 moves down very close to —15 volts as the transistor saturates and conducts current through R1 218 and R1239. The output of the feedback am plifier steps positive pulling the target backplate w ith it. This increases the operating level of the CRT and the entire target area is w ritten. When Q1216 turns on, the negative-going step produced at its collector is also coupled through C1214, which turns CR1212 off, ensuring cutoff of Q1210. Cl 214 begins to discharge through R1214, and after an RC-controlled period of time the current through R1214 has diminished sufficiently to allow the voltage at the anode of CR 1212 to rise above the turn-on level. The base of Q1210 is also raised to the turn-on level, and the m ultivibrator is switched back to its quiescent state. While Q1216 is conducting, the charge on C1219 is removed. When G1216 turns o ff, its collector rises rapidly and is clamped slightly above ground by CR1219. This produces a positive-going step which is coupled through C l219, reverse biasing CR1220. This positive movement is applied to the input of the feedback am plifier, causing the output to step sharply negative well below the rest poten­ tial. As C1219 charges, the voltage at the junction o f R1220-R1222 decays at an RC-controlled rate until CR1220 turns on and clamps it at about —15.5 volts. This negative-going sawtooth voltage is applied to the feedback am plifier, which produces a positive-going sawtooth at its output to raise the backplate to the ready-to-write state. When the CRT is shifted from the conventional mode to the store mode, pushing the store button grounds C l200, which produces a negative trigger to switch the Erase M u lti­ vibrator to prepare the target fo r storage by applying an erase waveform. Bootstrapping maintains operating voltage fo r Q1232 and Q1235 during the fade-positive portion of the erase waveform when the em itter of Q1235 is pulled positive. The voltage drop across zener diode VR1236 sets the base of Q1238 approximately 120 volts below the em itter o f Q1235. This voltage drop is kept constant under dynamic conditions by the essentially constant current established through R 1236, which is clamped by the Q1238 forward bias voltage. When the em itter of Q1235 is suddenly stepped positive by the erase waveform, the base of G1238 is stepped positive by the same amplitude. Q1238 em itter follow s the base, and the positive-going step is coupled through C l235 to raise the collector of Q1235 positive by essentially the same amplitude as that at its em itter, thus maintaining a fairly constant collector-to- em itter voltage. This action reverse biases CR1235, tem po­ rarily disconnecting the -i-300-volt supply. When the fade positive pulse is terminated and the em itter o f Q1235 is pulled negative, CR1237 turns o ff, disconnecting the boot­ strap circuit and allowing the collector of Q1235 to return to its +300-volt level. Enhance Generator W riting speed is prim arily a function of the w riting gun beam current density and physical properties of the storage tube. A t very fast sweep speeds, the w riting beam does not charge the scanned portion of the target sufficiently to shift it to the stored state, and the flood gun electrons discharge the small deposited charge back down to the rest potential before the next sweep. W riting beyond the normal w riting speed of the CRT is attained through the process of enhancement or integra­ tion. First to be discussed w ill be enhancement. The enhance generator produces an approximate two- millisecond negative-going pulse which is applied to the feedback am plifier summing point, resulting in a positive­ going pulse to the target backplate. This conditions the target so that less w riting gun current is required to shift the scanned section to the stored state. Q1245, Q1246, and their associated circuitry form a monostable m ultivibrator. Operation of this circuit is 3-28

either ENHANCE switch (S90C or S92C) is pushed in, Q1245 has a conduction path to ground through R1245. Q1245 saturates and the low voltage-level at the collector o f Q1245 keeps Q1246 turned o ff. The negative-going portion of the Enhance Trigger pulse from the Sweep circu it is coupled through C l240 to switch the Enhance M u ltivibrator. Q1245 turns o ff and Q1246 turns on. The collector of Q1246 snaps down to about —15 volts producing a negative-going step which is coupled through C l246, and turns o ff CR1245. The length of tim e that the m u ltivib ra to r remains in this state, and thus the pulse w id th , is determined by the values of R1244 and C1246. The setting o f the ENHANCE LE V E L control, R92, deter­ mines the am plitude of the pulse which is applied to the feedback am plifier summing point. 1 integrate The second fast w ritin g technique to be discussed is integration. In this mode of operation, the flood gun beam is interrupted m om entarily, allowing the w ritin g gun beam to sum small amounts o f charge fo r successive sweeps so th a t when the flood electrons are again turned on, the scanned target area shifts to the stored state. This is accomplished by pressing the IN TEG R A TE switch, S94, which disconnects the flood gun cathodes. This also connects —75 volts to the error signal input term inal of the high-voltage regulator c irc u it through R960 to sh ift the high voltage slightly, correcting fo r the deflection sensi­ tiv ity changes that occur when the flood guns are turned o ff. Releasing the IN TEG R A TE switch, then, allows the display to sh ift to the stored state. 3-29

434 Change info rm a tio n, i f any, affecting this section w it! be fo u n d a t the rear o f the manual. Introduction This section o f the manual contains maintenance in fo r­ m ation fo r use in preventive maintenance, corrective maintenance or troubleshooting of the 434. Cabinet Removal Dangerous potentials exist a t several p o in ts through­ o u t this instrum ent. When the instrum ent is operated w ith the covers removed, do n o t touch exposed connections o r components. Some transistors may have elevated cases. Disconnect pow er before cleaning the instrum ent o r replacing parts. The cabinet can be removed from the oscilloscope as follow s: 1. Unwrap the power cord from the instrum ent feet. 2. Loosen the phillips-head screw located in each instru­ m ent fo o t. See Fig. 4-1, 3. Remove the rear ring assembly from the rear o f the instrum ent. 4. Slide the cabinet to the rear and remove the oscillo­ scope. The R432 can be removed from its cabinet in a similar manner. T o replace the instrum ent in its wrap-around cabinet, reverse the removal procedure. The portable w rap­ around cabinet should be installed w ith the carrying handle p iv o t p o in ts positioned tow ard the bottom of the instrum ent. PR EVENTIVE M AIN TEN AN C E Genera! Preventive maintenance consists of cleaning, visual in s p e c tio n , lu b ric a tio n , etc. Preventive maintenance Fig. 4-1. R em oving w rap -a ro u n d cabinet. perform ed on a regular basis may prevent instrum ent break­ down and w ill improve the re lia b ility of this instrum ent. The severity o f the environm ent to w hich the 434 is subjected determines the frequency of maintenance. A convenient tim e to perform preventive maintenance is preceding recalibration o f the instrum ent. Cleaning General. The 434 should be cleaned as often as opera­ ting conditions require. A ccum ulation of d irt in the instru­ m ent can cause overheating and com ponent breakdown. D irt on components acts as an insulating blanket and prevents efficie n t heat dissipation. It also provides an elec­ trical conduction path w hich may result in instrum ent failure. The cabinet provides protection against dust in the in terior o f the instrum ent. Operation w ith o u t the cabinet in place necessitates more frequent cleaning. The fro n t cover provides dust protection fo r the fro n t panel and the CRT face. The fro n t cover should be installed fo r storage or transportation. 4-1

m ight damage the plastics used in this instrum ent. A vo id chemicals which contain benzene, toluene, xylene, acetone o r sim ilar solvents. Exterior. Loose dust accumulated on the outside of the 434 can be removed w ith a soft cloth or small paint brush. The paint brush is particularly useful fo r dislodging d irt on and around the front-panel controls. D irt w hich remains can be removed w ith a soft cloth dampened in a m ild deter­ gent and water solution. Abrasive cleaners should n o t be used. CRT. Clean the blue plastic light filte r and the CRT face w ith a soft, lint-free cloth dampened w ith denatured alcohol or a m ild detergent and water solution. The optional CRT mesh filte r can be cleaned in the fo llow ing manner. 1. Hold the filte r in a vertical position and brush lightly w ith a soft No. 7 w atercolor brush to remove light coatings o f dust and lint. 2. Greasy residues or dried-on d irt can be removed w ith a solution of warm water and a neutral pH liquid detergent. Use the brush to lig h tly scrub the filte r. 3. Rinse the filte r thoroughly in clean water and allow to air dry. 4. If any lin t or d irt remains, use clean low-pressure air to remove. Do n o t use tweezers or other hard cleaning tools on the filte r, as the special finish may be damaged. 5. When not in use, store the mesh filte r in a lint-free dust-proof cantainer such as a plastic bag. Interior. Dust in the in terior of the instrum ent should be removed occasionally due to its electrical conductivity under high-hum idity conditions. The best way to clean the in terior is to blow o ff the accumulated dust w ith d ry, low- pressure air. Remove any d irt which remains w ith a soft paint brush or a cloth dampened w ith a m ild detergent and water solution. A cotton-tipped applicator is useful fo r cleaning in narrow spaces or fo r cleaning c ircu it boards. Lubrication The re lia b ility o f potentiom eters, cam switches and other moving parts can be m aintained if they are kept properly lubricated. Lubricate switch detents w ith a heavier grease (e.g., T e ktro n ix Part No. 006-0219-00). P otentio­ meters w hich are not perm anently sealed should be lu b ri­ cated w ith a lubricant which does not affect electrical characteristics (e.g., T e ktro n ix Part No. 006-0220-00). A lubrication k it containing these lubricants and instructions is available from T e ktro n ix, Inc. Order T e ktro n ix Part No. 003-0342-01. The only portions o f a cam switch th a t require lubrication are the detents and the bushings. No lubricant should be applied to the cams or contacts of a cam switch. The correct lubricant fo r the detents and bushings is available by ordering T e ktro n ix Part No. 006-1353-00. Transistor Checks Periodic checks of the transistors in the 434 are not recommended. The best check o f transistor performance is actual operation in the instrum ent. More details on checking transistor operation are given under T rouble­ shooting. Recalibration To assure accurate measurements, check the calibration o f this instrum ent after each 1000 hours of operation or every six months if used infrequently. In addition, replace­ m ent of components may necessitate recalibration o f the affected circuits. Complete calibration instructions are given in the C alibration section. The calibration procedure can also be helpful in local­ izing certain troubles in the instrum ent. In some cases, m inor troubles may be revealed and/or corrected by recalibration. TROUBLESHO O TING Introduction The fo llow ing inform ation is provided to facilitate troubleshooting o f the 434. Inform ation contained in other sections should be used along w ith the fo llow ing inform a­ tion to aid in locating the defective com ponent. An under­ standing of the circu it operation is very helpful in locating troubles. See the C ircuit D escription section fo r complete inform ation. Troubleshooting Aids Diagrams. Complete circu it diagrams are given on fold- out pages in the Diagrams section. The com ponent number and electrical value of each com ponent in this instrum ent are shown on the diagrams. Im portant voltages and wave­ form s are also shown on the diagrams. The portions of the circu it mounted on the c ircu it boards are enclosed w ith a blue line. <§> 4-2

section show the c irc u it boards used in the 434. Fig. 4-5 shows the location o f each board w ith in the instru­ m ent. Each electrical com ponent on the boards is id e n ti­ fied by its c irc u it num ber. These pictures, used along w ith the diagrams, aid in locating the com ponents m ounted on the c irc u it boards. Wiring Color-Code. A ll insulated w ire and cable used in the 434 is color-coded to fa cilita te c irc u it tracing. Table 4-1 gives the w iring color-code fo r the pow er-supply voltages used in this instrum ent. TABLE 4-1 Power Supply Wiring Color Code S upply Background Color Stripe — 15 v o lt Purple Black + 15 vo lt Red Black + 115 v o lt Red B row n +250 v o lt Red Orange Resistor Color-Code. In ad d ition to the brow n com ­ position resistors, m etal-film resistors and some w ire-w ound resistors are used in the 434. The resistance o f a w ire- w ound resistor is printed on the body o f the com ponent. The resistance values o f com position resistors and metal- film resistors are color-coded on the com ponents w ith E IA color-code (some m etal-film resistors may have the value printed on the body). The color-code is read starting w ith the stripe nearest the end of the resistor. C om position resistors have fo u r stripes w hich consist of tw o significant figures, a m u ltip lie r and a tolerance value (see Fig. 4-2). M etal-film resistors have five stripes consisting o f thrt-' significant figures, a m u ltip lie r and a tolerance value. Capacitor Marking. The capacitance values o f com m on disc capacitors and small electrolytics are marked in m icro ­ farads on the side o f the com ponent body. The w hite ceram ic capacitors used in the 434 are color coded in pico­ farads using a m odified E IA code (see Fig. 4-2). Diode Color-Code. The cathode end o f each glass- encased diode is indicated by a stripe, a series o f stripes or a dot. For m ost silicon or germ anium diodes w ith a series of stripes, the color-code identifies the three significant digits Com position Resistors: M etal-Film Resistors: Ceramic Capacitors: Resistor and Capacitor Color Code O © © — 1st, 2nd and 3rd significant figu n © — m u ltip lier; ( J ) —tolerance; — tem perature coefficient. Color Signifi­ cant Figures M ultiplier Tolerance Resis­ tors Capaci­ tors Resis­ tors Capaci­ tors Silver . . . io-= ± 1 0 % — G old — 10-* — ± 5 % Black 0 1 1 — ± 2 0 % or 2 pF* Brown 1 10 10 ± 1 % ± 1 % or 0.1 pF* Red 2 10- 102 ± 2 % ± 2 % Orange 3 1.0* 103 ± 3 % ± 3 % Yellow 4 104 104 ± 4 % + 100% - 0 % Green 5 105 105 ± 0 .5 % ± 5 % or 0.5 pF* Blue 6 10° 10° — Violet 7 — . . . G ray 8 10-- + 8 0 % -2 0 % or 0.25 pF* W hite 9 10-1 ± 1 0 % or 1 pF* (none) ± 2 0 % ± 1 0 % or 1 pF* ♦ For capacitance o f 10 pF or less. NOTE: ( T ) a n d /o r ^ C ) color code fo r capacitors depends upon m anufacturer and capacitor type. M a y not be present in some cases. 4-3 Fig. 4-2. C o lo r-co d e resistors and ce ra m ic cap acitors.

system (e.g., a diode color-coded pink or blue-brown-gray- green indicates T ektronix Part Number 152-0185-00). The cathode and anode ends of a metal-encased diode can be identified by the diode symbol marked on the body. See Fig. 4-3. Semiconductor Lead Configuration. Fig, 4-4 shows the lead configurations of the semiconductors used in this instrument. This view is as seen from the bottom o f the device. Troubleshooting Equipment The follow ing equipment is useful for troubleshooting the 434. Fig. 4-3. D iode p o la rity m arkings. 1. Transistor Tester Description: Tektronix Type 576 Transistor-Curve Trace or equivalent. Purpose: To test semiconductors used in this instru­ ment. 2. M ultim eter Description: VTVM , 10 megohm input impedance and 0 to 500 volts range; ohmmeter, 0 to 50 megohms. Accuracy, w ithin 3%. Test probes must be insulated to prevent accidental shorting. Purpose: To check voltages and for general trouble­ shooting in this instrument. NOTE A 20,000 ohm s/vott VOM can be used to check the voltages in this instrum ent i f allowances are made fo r the circu it loading o f the VOM a t high-impedance points. 3. Test Oscilloscope Description: DC to 25 MHz frequency response, one m illivo lt to five volts/division deflection factor. A 10X probe should be used to reduce circuit loading. Purpose: To check waveforms in this instrument. 4. Isolation Transformer Description: Primary to secondary ratio of 1:1; capable of supplying operating power for this instrument. Purpose: To isolate power input of this instrum ent from ground to allow grounding points in the internal power supply for troubleshooting purposes. Troubleshooting Techniques This troubleshooting procedure is arranged in an order which checks the simple trouble possibilities before pro­ ceeding w ith extensive troubleshooting. The first few checks assure proper connection, operation and calibration. If the trouble is not located by these checks, the remaining steps aid in locating the defective component. When the defective component is located, it should be replaced fo llo w in g th e replacem ent procedures given under Corrective Maintenance. 4-4

Unijunction ---------------' Transistor Transistor 4-5 Fig. 4-4. Electrode configuration for semiconductors used in this instrument.

T ransformer Primary Board A 14 Z-Axis Board A17 Storage Board 4-6

can indicate a trouble that does not exist. If there is any question about the correct fu n ctio n or operation of any control, see the Operating Instructions section. 2. Check Associated Equipment. Before proceeding w ith troubleshooting of the 434, check th a t the equipm ent used w ith this instrum ent is operating correctly. Check that the signal is properly connected and th a t the inter­ connecting cables are not defective. Also, check the power source. 3. Visual Check. Visually check the portion of the instrum ent in which the trouble is located. Many troubles can be located by visual indications such as unsoldered c o n n e c tio n s , broken wires, damaged circu it boards, damaged components, etc. 4. Check Instrument Calibration. Check the calibration of this instrum ent, or the affected circu it if the trouble appears in one circuit. The apparent trouble may only be a result of m isadjustm ent or may be corrected by calibration. Complete calibration instructions are given in the Calibra­ tio n section. 5. Isolate Trouble to a Circuit. To isolate trouble to a circuit, note the trouble sym ptom . The sym ptom often identifies the circu it in which the trouble is located. For example, poor focus indicates that the CRT circu it (includes high voltage) is probably at fault. When trouble sym ptom s appear in more than one circuit, check affected circuits by taking voltage and waveform readings. Incorrect operation o f all circuits often indicates trouble in the power supply. Check firs t fo r correct voltage o f the individual supplies. However, a defective com ponent else­ where in the instrum ent can appear as a power-supply trouble and may also affect the operation of other circuits. Table 4-2 lists the tolerances of the power supplies in this instrum ent. If a power-supply voltage is w ith in the listed TABLE 4-2 Power Supply Tolerance and Ripple Power Supply Tolerance Maximum Ripple (Peak-to-peak) Line Frequency 25 Kilohertz —15 vo lt W ithin 0.113 volt 10 mV 40 m V +15 volt W ithin 0.225 volt 10 mV 40 m V +115 volt W ithin 4.6 volts 0.5 volt 0.5 vo lt +250 volt W ithin 10 volts 1 volt 1 volt —75 volt W ithin 2.25 volts 1 volt 1 volt tolerance, the supply can be assumed to be w orking correctly. If outside the tolerance, the supply may be misadjusted or operating incorrectly. Use the procedure given in the C alibration section to adjust the power supplies. A fte r the defective circu it has been located, proceed w ith steps 6 through 8 to locate the defective com ­ ponents). 6. Check Circuit Board Interconnections. A fte r the trouble has been isolated to a particular circu it, check the pin connectors on the circu it board fo r correct connection. Figs. 8-1 through 8-23 show the correct connections for each board. The pin connectors used in this instrum ent also provide a convenient means of circu it isolation. For example, a short in a power supply can be isolated to the power supply itself by disconnecting the pin connectors fo r th a t voltage at the remaining boards. 7. Check Voltages and Waveforms. O ften the defective com ponent can be located by checking fo r the correct voltage or waveform in the circuit. Typical voltages and waveform s are given on the diagrams. N O TE Voltages and waveforms given on the diagrams are n o t absolute and may vary slightly between instru­ ments. To obtain operating conditions sim ilar to those used to take these readings, see the firs t diagram page. 8. Check Individual Components. The follow ing pro­ cedures described methods of checking individual com po­ nents in the 434. Components which are soldered in place are best checked by disconnecting one end. This isolates the measurement from the effects of surrounding circu itry. A . TRANSISTO RS. The best check o f transistor opera­ tion is actual performance under operating conditions. If a transistor is suspected of being defective, it can best be checked by substituting a new com ponent or one w hich has been checked previously. However, be sure that circuit conditions are not such that a replacement transistor m ight also be damaged. If substitute transistors are not available, use a dynam ic tester (such as T e ktro n ix Type 576). Static- type testers are not recommended, since they do n o t check operation under simulated operating conditions. © 4-7

The POWER switch m ust be turned o ff before rem ov­ ing o r replacing transistors. B. DIODES. A diode can be checked fo r an open or shorted condition by measuring the resistance between terminals. W ith an ohm m eter scale having an internal source o f between 800 m illivo lts and 3 volts, the resistance should be very high in one direction and very low when the meter leads are reversed. r ' — S C A U T I O N < Do n o t use an ohm m eter scale that has a high internal current. High currents may damage the diode. Do n o t measure tunnel diodes w ith an ohm m eter; use a dynam ic tester (such as a Tektronix Type 576 Transistor-Curve Tracer). C. RESISTORS. Check the resistors w ith an ohmmeter. See the Electrical Parts List fo r the tolerance of the resis­ tors used in this instrum ent. Resistors norm ally do n o t need to be replaced unless the measured value varies w idely from the specified value. D. INDUCTORS. Check fo r open inductors by check­ ing c o n tin u ity w ith an ohm m eter. Shorted or partially shorted inductors can usually be found by checking the waveform response when high frequency signals are passed through the circuit. Partial shorting often reduces high- frequency response (ro ll-o ff). E. CAPACITORS. A leaky or shorted capacitor can best be detected by checking resistance w ith an ohm m eter on the highest scale. Do not exceed the voltage rating of the capacitor. The resistance reading should be high after initial charge o f the capacitor. An open capacitor can best be detected w ith a capacitance meter or by checking whether the capacitor passes AC signals. 9. Repair and Readjust the Circuit. If any defective parts are located, fo llo w the replacement procedures given in this section. Be sure to check the performance o f any circu it th a t has been repaired or th a t has had any electrical components replaced. CORRECTIVE M AIN TEN AN C E General Corrective maintenance consists o f com ponent replace­ m ent and instrum ent repair. Special techniques required to replace components in this instrum ent are given here. Obtaining Replacement Parts Standard Parts. A ll electrical and mechanical part replacements fo r the 434 can be obtained through your local T e ktro n ix Field O ffice or representative. However, many of the standard electronic components can be obtained locally in less tim e than is required to order them from T e ktro n ix, Inc. Before purchasing or ordering replace­ ment parts, check the parts list fo r value, tolerance, rating and description. N O TE When selecting replacement parts, i t is im p o rta n t to remember that the physical size and shape o f a com ­ ponent m ay a ffe ct its perform ance in the instrum ent, p a rticu la rly a t high frequencies. AH replacement parts should be d ire ct replacements unless i t is know n that a d iffe re n t com ponent w ill n o t adversely a ffect instrum ent performance. Special Parts. In addition to the standard electronic components, some special components are used in the 434. These components are m anufactured or selected by Tek­ tro n ix , Inc. to meet specific performance requirements, or are manufactured fo r T e k tro n ix , Inc. in accordance w ith our specifications. These special components are indicated in the Electrical Parts List by an asterisk preceding the part number. Most o f the mechanical parts used in this instru­ m ent have been manufactured by T e ktro n ix, Inc. Order all special parts dire ctly from your local T e ktro n ix Field O ffice or representative. Ordering Parts. When ordering replacement parts from T e ktro n ix, Inc., include the fo llow ing inform ation: 1. Instrum ent type. 2. Instrum ent serial number. 3. A description o f the part (if electrical, include circu it num ber). 4. T e ktro n ix Part Number. Soldering Techniques W A R N I N G Disconnect the instrum ent from the pow er source before soldering. 4-8

40-w att pencil type soldering iron on the circu it boards. The tip of the iron should be clean and properly tinned fo r best heat transfer to the solder jo in t. A higher wattage soldering iron may separate the w iring from the base material. The follo w in g technique should be used to replace a com ponent on a circu it board. Most components can be replaced w ith o u t removing the boards from the instrum ent. > C A U T I O N i The Vertical M ode Switch, the attenuator and the Vertical In p u t A m p lifie r c irc u it boards are made o f m aterial easily damaged b y excessive heat. When soldering to these boards, do n o t use a soldering iron w ith a rating o f m ore than approxim ately 15 watts. A vo id prolonged applications o f heat to circuit-board connections. 1. G rip the com ponent lead w ith long-nose pliers. Touch the soldering iron to the lead at the solder connec­ tion. Do n o t lay the iron directly on the board as it may damage the board. 2. When the solder begins to m elt, pull the lead out gently. This should leave a clean hole in the board. If not, the hole can be cleaned by reheating the solder and placing a sharp object such as a toothpick into the hole to clean it out. A vacuum-type desoldering tool can also be used fo r this purpose. 3. Bend the leads of the new com ponent to f it the holes in the board. If the com ponent is replaced w hile the board is m ounted in the instrum ent, cut the leads so they w ill just protrude through the board. Insert the leads into the holes in the board so the com ponent is firm ly seated against the board (or as positioned originally). If it does not seat properly, heat the solder and gently press the com ponent into place. 4. Touch the iron to the connection and apply a small am ount o f solder to make a firm solder jo in t; do not apply too much solder. To protect heat-sensitive components, hold the lead between the com ponent body and the solder jo in t w ith a pair o f long-nose pliers or other heat sink. 5. Clip the excess lead that protrudes through the board (if not clipped in step 3). 6. Clean the area around the solder connection w ith a flux-rem over solvent. Be careful not to remove inform ation printed on the board. M etal Terminals. When soldering metal terminals, ordinary 60/40 solder can be used. Use a soldering iron w ith a 40- to 75-w att rating and a 1/8-inch wide wedge- shaped tip . Observe the follow ing precautions when soldering metal terminals: 1. A pply only enough heat to make the solder flo w freely. Use a heat sink to protect heat-sensitive com ­ ponents. 2. A p p ly only enough solder to form a solid connection. Excess solder may im pair the function o f the part. 3. If a w ire extends beyond the solder jo in t, clip o ff the excess. 4. Clean the flu x from the solder jo in t w ith a flux- remover solvent. Component Replacement W A R N IN G | Disconnect the instrum ent from the pow er source before replacing components. C ircuit Board Replacement. If a circu it board is damaged beyond repair, either the entire assembly includ­ ing all soldered-on components, or the board only, can be replaced. Part numbers are given in the Mechanical Parts List fo r either the com pletely wired or the unwired board. Most o f the components m ounted on the c ircu it boards can be replaced w ith o u t removing the boards from the instru­ ment. Observe the soldering precautions given under Solder­ ing Techniques in this section. Most o f the connections to the circu it boards in the instrum ent are made w ith pin connectors. However, some connections are soldered to the board. Use the follow ing procedure to remove a circu it board: 1. Disconnect all pin connectors from the board and unsolder any soldered connections. 2. Remove all screws holding the board to the chassis. 3. L ift the circu it board out of the instrum ent. Do not force or bend the board. 4-9

4. To replace the board, reverse the order of removal. Correct location o f the pin connectors is shown in Figs. 8-1 through 8-23. Replace the pin connectors carefully so they mate correctly w ith the pins. If forced into place incor­ rectly positioned, the pin connectors may be damaged. T ra n sisto r Replacement. Transistors should not be replaced unless actually defective. If removed from their sockets during routine maintenance, return them to their original sockets. Unnecessary replacement of transistors may affect the calibration of this instrum ent. When tra n ­ sistors are replaced, check the operation o f th a t part of the instrum ent which may be affected. POWER switch m ust be turned o ff before rem oving or replacing transistors. Replacement transistors should be of the original type or a direct replacement. Fig. 4-4 shows the lead configuration o f the transistors used in this instrum ent. Some plastic case transistors have lead configurations which do not agree w ith those shown here. If a transistor is replaced by a transistor made by a diffe re n t m anufacturer than the original, check the m anufacturer's basing diagram fo r correct basing. A ll transistor sockets in this instrum ent are wired fo r the basing used fo r metal-case transistors. Transistors w hich have heat radiators or are m ounted on the chassis use silicone grease to increase heat transfer. Replace the silicone grease when replacing these transistors. W A R N I N G Handle silicone grease w ith care. A v o id getting s ili­ cone grease in the eyes. Wash hands thoroughly after use. Cathode-Ray Tube Replacement. Use care when handling a CRT. Protective clothing and safety glasses should be w orn. Avoid striking it on any object which m ight cause it to crack or im plode. When storing a CRT, place it face dow n on a smooth surface w ith a protective cover or soft mat under the faceplate to protect it from scratches. The CRT shield shpuld also be handled carefully. This shield protects the CRT display from d istortion due to magnetic interference. If the shield is dropped or struck sharply, it may lose its shielding a b ility. The fo llow ing procedure outlines the removal and replacement of the cathode-ray tube: A . R E M O V A L: 1. Rem ove the wrap-around cabinet as described previously. 2. Remove the light filte r. 3. Remove the cover plate from the rear casting. 4. Remove the socket from the base of the CRT. 5. Remove the 2 Axis C ircuit Board from the instru­ ment. 6. Disconnect the deflection plate leads from the neck o f the CRT. Be careful not to bend or excessively squeeze the pins. 7. Remove the tw o screws securing the rear of the CRT shield to the rear casting. 8. Remove the delay-line assembly from the CRT shield by removing the lone screw in the m iddle of the delay line. 9. Remove the tw o screws securing the CRT shield to the fro n t casting. 10. Remove the CRT assembly from the instrum ent. 11. Loosen the CRT clamp at the rear o f the CRT shield. 12. Hold one hand on the CRT faceplate and push forw ard on the CRT base w ith the other. As the CRT starts o u t o f the shield, grasp it firm ly . When the CRT is free of the clamp, slide the shield com pletely o ff the CRT. B. REPLACEM ENT: 1. Loosen the fo u r hex-head screws on the fro n t part of the CRT shield. 2. Insert the CRT in to the shield. Loosen the tw o securing screws inside the rear of the CRT shield. Be sure the faceplate of the CRT is flush or slightly recessed w ith the fro n t opening o f the CRT shield. Do not tighten the CRT clamp yet. 4-10

insert the CRT assembly into the instrum ent. Be sure the CRT faceplate seats properly in the fro n t casting. The lip on the upper edge of the fro n t of the CRT shield must engage the slot in the fro n t casting. 4. Replace the tw o screws securing the rear of the CRT shield to the rear casting. 5. Seat the CRT firm ly against the fro n t casting, making sure the light mask is positioned correctly. C orrectly align the CRT in the opening in the fro n t casting by positioning and tightening the fo u r hex-head screws loosened pre­ viously in step 1. Also tighten the three screws inside the rear of the CRT shield. Recommended tightening torque fo r the clamp screw is 4 to 7 inch/lbs. 6. Install the CRT socket on the base of the CRT. 7. Install the Z A xis C ircuit Board. 8. Reconnect the deflection plate leads on the neck of the CRT. Be careful not to bend or excessively squeeze the pins. 9. Re-install the delay-line assembly on the bottom of the CRT shield. 10. Re-install the cover plate on the rear casting. 11. Re-install the CRT light filte r in the fro n t casting. 12. Recheck instrum ent calibration. Fuse Replacement. The only fuse used in the instru­ m ent is the power-line fuse. Use only a 1 1/2 ampere fast-blow fuse as a replacement. Power Transform er Replacement. If the power trans­ form er becomes defective, contact your local T e ktro n ix Field O ffice or representative fo r a w arranty replacement (see w arranty note in the fro n t of this manual). Be sure to replace only w ith a direct replacement T ektro n ix trans­ form er. A fte r the transform er is replaced, check the per­ formance of the complete instrum ent. The components located in the power-supply com part­ m ent can be reached fo r maintenance by using the fo llo w ­ ing procedure: 1. Remove the wrap-around cabinet from the instru­ ment as described earlier in this section. 2. Lay the instrum ent dow n fla t w ith the power-supply com partm ent edge facing you. 3. Remove the tw o screws securing the com partm ent shield to the rear casting. 4. Loosen the tw o screws securing the com partm ent shield to the forward power-supply com partm ent bulkhead and slide the shield out o f the instrum ent. W A R N I N G I Line AC , high voltage, and stored DC are present in this com partm ent. I t is recommended the instrum ent n o t be operated w ith this shield removed. A fte r gaining access to the power-supply com partm ent, the power transform er assembly can be removed as follow s: 1. Remove the Power Supply Secondary circu it board. 2. Remove the plastic insulating sheet that mounts be­ neath the Power Supply Secondary circu it board. 3. Remove the metal cover to the enclosure containing the power-supply transform er assembly. 4 . R em ove th e tra n s fo rm e r assembly from the enclosure. Be careful not to bend the pins. Recalibration A fte r Repair A fte r any electrical com ponent has been replaced, the calibration o f that particular circu it should be checked, as well as the calibration of other closely related circuits. Since the power supply affects all circuits, calibration of the entire instrum ent should be checked if w o rk has been done in the power supply or if the transform er has been replaced. Instrum ent Repackaging If the 434 is to be shipped fo r long distances by commercial means of transportation, it is recommended that the instrum ent be repackaged in the original manner fo r m axim um protection. The original shipping carton can be saved and used fo r this purpose. The Repackaging illus­ tration in the Mechanical Parts Illustrations shows how to repackage the 434 and gives the part numbers fo r the repackaging components. New shipping cartons can be obtained from T e ktro n ix, Inc. C ontact yo u r local T e k­ tro n ix Field O ffice or representative. 4-11

Change inform ation, i f any, affecting this section w ill be fou n d a t the rear o f this manual. Introduction To assure instrum ent accuracy, check the calibration of the 434 every 1000 hours o f operation, or every six months if used infrequently. Before complete calibration, th o r­ oughly clean and inspect this instrum ent as outlined in the Maintenance section. Tektronix Field Service T e ktro n ix, Inc. provides complete instrum ent repair and recalibration at local Field Service Centers and the Factory Service Center. Contact your local T ektronix Field O ffice or representative fo r fu rth e r inform ation. Using This Procedure To aid in locating a step in the C alibration procedure, an index is given p rior to the complete procedure. C om pletion o f each step in the fu ll C alibration procedure insures that this instrum ent meets the electrical specifications given in Section 1. Where possible, instrum ent performance is checked before an adjustm ent is made. For best overall instrum ent performance when perform ing a complete cali­ bration procedure, make each adjustm ent to the exact setting even if the C HECK— is w ith in the allowable to le r­ ance. A partial calibration is often desirable after replacing components, or to touch up the adjustm ent of a portion of the instrum ent between major recalibration. T o adjust only part of the instrum ent, set the controls as given under Prelim inary C ontrol Settings and start w ith the nearest Equipm ent Required List preceding the desired portion. To prevent unnecessary recalibration of other parts o f the instrum ent, readjust only if the tolerance given in the C HECK— part of the step is not met. If re-adjustment is necessary, also check the calibration o f any steps listed in the IN T E R A C T IO N — part of the step. IM P O R T A N T N O TE AH waveforms shown in this procedure were taken w ith a Tektronix Oscilloscope Camera System, unless otherwise noted. Lim its, tolerances, and waveforms in this procedure are given as calibration guides and should n o t be interpreted as instrum ent specifications except as specified in Section 1. TEST EQUIPMENT REQUIRED General The follow ing test equipm ent and accessories, or their equivalent, are required fo r complete calibration of the 434. Specifications given fo r the test equipm ent are the m inim um necessary fo r accurate calibration. Therefore, the specifications of any test equipm ent used must meet or exceed the listed specifications. A ll test equipm ent is assumed to be correctly calibrated and operating w ith in the listed specifications. Detailed operating instructions fo r the test equipm ent are n o t given in this procedure. Refer to the instruction manual fo r the test equipm ent if more inform a­ tion is needed. Special Calibration Fixtures Special T ektronix calibration fixtures are used in this procedure only where they facilitate instrum ent calibration. T hese special calibration fixtures are available from T e ktro n ix, Inc. Order by part number through your local T e ktro n ix Field O ffice or representative. Calibration Equipm ent Alternatives A ll of the listed test equipm ent is required to com pletely calibrate this instrum ent. The C alibration procedure is based on the firs t item o f equipm ent given as an example of applicable equipm ent. When other equipm ent is substi­ tuted, control settings or calibration setup may need to be altered slightly to meet the requirements of the substitute equipm ent. If the exact item of test equipm ent given as an example in the Test Equipm ent list is not available, first check the Specifications colum n carefully to see if any other equipm ent is available which m ight suffice. Then check the Usage colum n to see w hat this item o f the test equipm ent is used fo r. If used fo r a check or adjustment which is of little or no importance to your measurement requirements, the item and corresponding step(s) can be deleted. The follow ing procedure is w ritten to com pletely check and adjust the 434 to the Performance Requirements given in Section 1. If the applications fo r which you w ill use the 434 do not require the fu ll available performance from the 434, this procedure and the required equipm ent list can be sho rte n e d accordingly. For example, only the basic measurement capabilities of this instrum ent can be verified by checking vertical deflection accuracy w ith a Standard A m plitude Calibrator, vertical square-wave response w ith fast-rise Square-Wave Generator (such as the T ektro n ix Type 106), and the horizontal tim ing using a Tim e-Mark Generator. 5-1

with AC voltmeter Capable of supplying 66 volt- Amperes at an output voltage of 120 VAC. Power Supply adjustment. General Radio W10MT3W Variac Autotransform er. 2 . T e s t- o s c il loscope system. B a n d w id th , DC to 25 m e g a h e r tz ; m in im u m d e fle c tio n fa c to r, fiv e m illivolts/division; accuracy, w ithin 3%. A djust Power Supply opera­ tion, CRT grid bias, Sweep Generator offset adjustment, and Z-Axis Compensation. a. Tektronix 7503 or 7504 Oscilloscope w ith 7A15 or 7A16 A m plifier and 7B50 or 7B52 Time-Base plug-in units, and P6053 Probe. b. Tektronix 432 Oscillo­ scope w ith a P6011 Probe and a P6006 Probe. 3. Precision DC voltmeter Range, zero to 500 volts; accuracy, w ithin 0.2%. Calibrator output accuracy check and adjustment. Power Supply adjustment. a. T ektronix 7D13 Digital M ultim eter (test oscilloscope must have Readout System). b. Fluke Model 825A D iffer­ ential DC Voltm eter. 4. DC voltmeter Range, zero to 4000 volts; accuracy, checked to w ithin 1% at —3940 volts. High voltage power supply adjustment. a. T rip le tt Model 630-NA. b. Simpson Model 262. 5. Time-mark generator Marker outputs, 20 nano­ seconds to 5 seconds; marker accuracy, w ithin 0.1%. CRT geometry check and a d ju s tm e n t. H o riz o n ta l tim ing check and adjustment. C alibrator repetition rate check and adjustment. a. T ektronix 2901 Time-Mark Generator. b. T ektronix 184 Time-Mark Generator. 6. M e d iu m -F re q u e n cy constant-amplitude signal generator Frequency, 350 kilohertz to 25 megahertz; reference fre­ quency, 50 kilohertz; output amplitude, variable from five m illivolts to five volts peak to peak into 50 ohms; amplitude accuracy, constant w ithin 3% of reference as output fre­ quency changes. External Z-axis operation ch e ck. Vertical am plifier bandwidth check. Trigger cir­ cuit check and adjustment. a. Tektronix 191 Constant Am plitude Signal Generator. b. General Radio 1 211 -C w ith 1263-C Am plitude Regulating Power Supply. 7. Low-frequency signal generator Frequency, 100 hertz to 30 kilohertz; output amplitude, variable from 35 m illivolts to 40 volts. Trigger circuit check and adjustment. a. General Radio 1310-B Oscillator. 8. Standard Am plitude Calibrator Am plitude accuracy, 0.25%; signal amplitude, 5 m illivolts to 50 volts; output signal, one-kilohertz square wave. Vertical am plifier gain check a. Tektronix calibration fix- and adjustment. External and t u r e P a r t N u m b e r horizontal gain check. 067-0502-01. 9. Square-wave generator Frequency, one kilohertz and 100 kilohertz; risetime, one nanosecond or less from fast- rise output. Vertical am plifier compensa- a. T e k tro n ix Type 106 tion checks and adjustments. Square-Wave Generator. _ 5-2

Calibration—434 Description Minimum Specifications Usage Example 10. Current Probe Maximum Current, 5 A RMS. Power Supply checks and adjustments. Not necessary for periodic recalibration. a. Tektronix P6021 AC Cur­ rent Probe w ith 011-0105-00 Passive Term ination. 11. Adapter Connectors, GR874 and BNC female. Vertical am plifier bandwidth checks. Trigger circuit checks and adjustments. a. Tektronix Part Number 017-0063-00. 12. Input normalizer RC time constant, 24 pico­ farads times one megohm. Standardize input RC time constant. a. Tektronix Part Number 067-0539-00. 13. T connector Connectors, BNC. External trigger operation checks. External Z Axis operation check. ADD mode operation check. a. Tektronix Part Number 103-0030-00. 14. Attenuator A ttenuation ratio, 10X; con­ nectors BNC, impedance, 50 ohms. Vertical am plifier compensa­ tion checks and adjustments. a. Tektronix Part Number 011-0059-01. 15. Termination Impedance, 50 ohms; accu­ racy, ±2%; connectors, BNC. External Z Axis operation c h e ck. Vertical am plifier bandwidth check. Trigger cir­ cuit operation checks and adjustments. a. Tektronix Part Number 011-0049-01. 16. Cable (two required) Impedance, 50 ohms; type, RG-58/U; length, 42 inches; connectors, BNC. Used throughout procedure for signal interconnection. a. T ektronix Part Number 012-0057-01. 17. Screwdriver Three-inch shaft, 3/32-inch bit. Used throughout procedure to adjust variable resistors. a. Xcelite R-3323. 1 8 . L o w -c a p a c ita n c e screwdriver 1 1/2-inch shaft. Used throughout procedure to adjust variable capacitors. a. Tektronix Part Number 003-0000-00. 19. Tuning tool Fits 5/64-inch (ID) hex cores. V e rtic a l a m p lifie r high- frequency compensation ad­ justments. a. Tektronix Part Number 003-0307-00 (handle) and 003-0310-00 (insert). 5-3

PROCEDURE Power Supply and Display A djustm ent 1. Preset Power Supply Current Sense Adjustm ent 2. Adjust —15-Volt Power Supply Page 5-6 Page 5-7 24. Adjust Channel 2 V O LT S /D IV Switch Compensation 25. Adjust High Frequency Compensation 26. Check Vertical A m p lifie r Bandwidth 27. Check 5 MHz BW Bandwidth 3. Adjust Power Supply Current Sense Adjustm ent Page 5-7 Trigger C ircuit A djustm ent 4. Adjust High-Voltage Power Supply Page 5-8 28. A djust Trigger Level Centering 5. Adjust CRT Grid Bias Page 5-8 29. Adjust CH 1 and COMP Trigger DC Level 6. Adjust Focus Range and Astigmatism Page 5-9 30. Check Trigger C ircuit Operation 7. Adjust Trace Rotation Page 5-9 31. Check Single Sweep Operation 8. Pre-Set C ollim ation and Storage Target Levels Page 5-9 32. Check TRIGGER LE V E L Control Range 9. Adjust Upper and Lower Non-Store Levels Page 5-9 33. Check Line Triggering 10. Adjust Upper and Lower Store Levels Page 5-10 11. Adjust Collim ation Page 5-11 H orizontal System A djustm ent 12. Check Stored W riting Speed Page 5-11 34. Adjust Sweep Generator Offset Adjustm ent 13. Adjust Geometry Page 5-12 35. Adjust Sweep Cal Adjustm ent 14. Check BEAM FINDER Operation Page 5-12 36. Adjust Horizontal Gain 15. Check External Z Axis Operation Page 5-13 37. Adjust Magnifier Registration 16. Check Chopped Operation Page 5-13 38. Check Variable T1ME/D IV Range 39. Adjust High Speed Tim ing Vertical System A djustm ent 17. Adjust Channel 1 Balance 40. Check T IM E /D IV Accuracy Page 5-14 18. Adjust Channel 2 Balance Page 5-14 41. Check Magnified Sweep Accuracy 19. Adjust CH 1 and CH 2 G AIN Page 5-15 42. Check High Speed Magnified Tim ing Accuracy 20. Check CH 1 Variable V O LT S /D IV Range and A ttenuator Accuracy Page 5-15 43, Check External Horizontal Sensitivity 21. Check CH 2 Variable V O LT S /D IV Range and A ttenuator Accuracy Page 5-16 22. Check ADD Mode Operation Page 5-16 C alibrator C ircuit A djustm ent 44. A djust Calibrator O utput Voltage A m plitude 23. Adjust Channel 1 V O LT S /D IV Switch Page 5-16 Compensation 45. Adjust Calibrator Repetition Rate Page 5-17 Page 5-17 Page 5-19 Page 5-20 Page 5-21 Page 5-21 Page 5-22 Page 5-22 Page 5-23 Page 5-23 Page 5-24 Page 5-24 Page 5-25 Page 5-25 Page 5-25 Page 5-25 Page 5-26 Page 5-26 Page 5-26 Page 5-26 Page 5-27 Page 5-27 5-4

NOTE This instrum ent should be adjusted a t an ambient temperature o f +25°C (±5°C) fo r best overall accuracy. NOTE Titles fo r externaI controls o f this instrum ent are capitalized in this procedure (e.g., IN TE N S ITY ). Internal adjustments are in itia l capitalized only te.g.. Sweep Cal). 1. Remove the wrap-around cabinet from the 434 in the manner given in section 4 of this manual. 2. Connect the autotransformer to a suitable power source. NOTE I f a line voltage source o f exactly 120 VAC RMS is available, it w ill not be necessary to use the au to transformer. 3. Connect the 434 to the autotransformer output. 4. Set the autotransformer output voltage for exactly 120 VAC RMS. 5. Set the controls as given under Preliminary Control Settings. A llow at least 30 minutes warmup before proceeding. Preliminary Control Settings Preset the instrum ent controls to the settings given below when starting a Calibration procedure. POWER/IIMTENSITY POSITION (vertical and horizontal) 5 MHz BW IN VER T Input Coupling Vertical Mode V O LTS /D IV Variable VO LTS /D IV TRIGGER SOURCE TRIGGER COUPLING TRIGGER LEVEL TRIGGER SLOPE Sweep MODE T IM E /D IV VAR T IM E /D IV ENHANCE LEVEL STORE (upper & lower) ENHANCE (upper & lower) Pulled out and rotated fu lly counterclockwise Midrange Pushed in Pushed in AC CH 1 .1 V CAL COMP AC Midrange + SINGLE SWEEP 1 ms CAL Fully counterclockwise Non-store O ff NOTES

Equipment Required 1. Test Oscilloscope 7. Current Probe 2. Medium-Frequency Constant-Am plitude Signal 8. Adapter (GR874 and BNC female connectors) Generator 3. Time-Mark Generator 4. Precision DC Voltm eter 5. DC Voltm eter 6. Autotransform er 9. 50 El BNC Term ination 10. 42-Inch 50 £2 BNC Cables (2 ea.) 11. BNC T Connector 12. 3-Inch Screwdriver Control Settings Preset instrument controls to the settings given under Preliminary Control Settings. 1. Preset Power Supply Current Sense Adjustment NOTE This step need be perform ed only if the setting o f R1074 has become grossly misad/usted, or if major circuit components in the pow er supply have been replaced that w ould cause the setting o f R 1074 to be incorrect, i f the power supply portion o f this instrum ent has been working correctly, proceed with step 2. a. Turn o ff instrument power, disconnect the power line, and remove the power supply compartment shields to provide access to leads connected to transistor Q1080. See Fig. 5-1. Under certain conditions. C l016 can remain charged fo r several minutes. I f one o f the two neon bulbs on the Primary Power Supply circuit board is s till lit with instrum ent power turned o ff, wait u n til both lights are extinguished before attem pting to discharge C l016 and/or working in the pow er supply area. b. Connect the P6021 Current Probe around the collec­ tor lead (grey-yellow wire to pin 2 of P I02 on Power Supply Primary circuit board) of Q1080 w ith the arrow on the head of the Current Probe pointing to the collector of Q1080. c. Connect the Passive Term ination for the Current Probe to the input connector of the test oscilloscope and connect the Current Probe to the Passive Term ination. d. Reconnect the line cord and turn on instrument power to the 434 under test. W A R N I N G I Line AC, high voltage, and stored DC are present in the Power Supply compartment. Primary Power Supply circu it common and guard box are elevated to line voltage potential. Do n o t touch the guard box or connect test equipment ground leads to the circuit common w ithout first connecting the 434 under test to the power tine through a 1:1 ratio isolation transformer that is insulated fo r 600 volts or more between prim ary and secondary. Exercise extreme c a u t i o n when working in this area w ith the com partm ent shields removed. a loso C ollecto r Lead P6021 C urrent Probe (N ote p o la rity sym bols) Fig. 5-1. Measuring Q 1980 co lle cto r current. 5-6

e. Set the sensitivity of the Current Probe Passive Ter­ mination to 10 m A /m V and the V olts/D iv switch of the test oscilloscope to 50 m V/div. Fig, 5-4. Lo ca tio n o f —1 5 -V o lt Power S upp ly Test P oint. f. CHECK—Test oscilloscope display of 4.4 divisions peak to peak (peak current measurement of 2.2 amperes). See Fig. 5-2. Repetition rate should be approximately 25 kilohertz (40 /us period). 2. A d ju s t-1 5 -V o lt Power Supply a. Connect the Precision DC Voltm eter between the -1 5 -v o lt power supply test point (negative lead of C l 107 on Power Supply Secondary circuit board; see Fig. 5-4) and ground. g. A D JU S T-C urrent Sense adjustment R 1074 (see Fig. b C H E C K -M eter reading of -1 5 volts, ±0.112 volt 5-3) fo r peak to peak display amplitude of 4.4 divisions, (±0.187 volt if the measurement is being made outside of ±0.2 division (2.2 amperes, ±0.1 ampere). the +20°C to ±30°C temperature range). Fig. 5-3. Lo cation o f C urrent Sense adjustm ent R1070. c. ADJUST— —15 Volts adjustment R1122 (see Fig. 5-4) fo r a meter reading of —15 volts, ±0.037 volt. d. Disconnect the Precision DC Voltm eter from the 434 under test. e. IN TER A C TIO N —May affect the operation of all circuits w ithin the 432. 3. Adjust Power Supply Current Sense Adjustment a. Obtain a display of the current waveform in the collector circuit of Q1080 in the manner given in Calibra­ tion Procedure step 1. NOTE i f step 1 was n o t perform ed, the need fo r the Current Probe can be eliminated by m onitoring the repetition rate o f the Power Supply Primary circuit using a test oscilloscope with a voltage probe connected to pin 1 o f plug P i 27 on the Z Axis circuit board. ® 5-7

second tim e period between current peaks. c. ADJUST—Current Sense adjustment R1074 (see Fig. 5-3) fo r 40 microseconds, ±one microsecond tim e period between current peaks. d. Disconnect all test equipment and re-install tbe Power Supply compartment shields. e. IN TER A C TIO N —May affect the operation of all circuits w ithin the 432. 4. Adjust High-Voltage Power Supply a. Connect the DC Voltm eter between the —3940 volt test point TP962 (see Fig. 5-5) and ground. b. CHECK—Meter reading of —3940 volts, ±98.5 volts (±118.2 volts if the measurement is being made outside of the +20°C to +30"C temperature range). c. ADJUST—High Voltage Adjust R963 (see Fig. 5-5) for a meter reading of —3940 volts, ±78.8 volts. d. Disconnect the DC Voltm eter from the 432 under test. . irj? JU ? JCRT„r,'s c v i\l9 fV ^ '.'3 t~?.,i+.a'^usXTOp/?*. Ioc?tio.o5 e. IN TER A C TIO N —May affect vertical gain, horizontal tim ing accuracy and CRT focus, astigmatism and geometry. NOTE I f the line voltage is w ithin the operating lim its o f the 432, (90 VAC to 264 VAC RMS), the 432 can be connected directly to the line, i f not, leave the 432 connected to the autotransformer fo r the remainder o f this procedure. 5. Adjust CRT Grid Bias and Z-Axis Compensa­ tion a. Attach a 10X probe to the test oscilloscope and connect the tip of the probe to test point TP924 on the Z Axis circuit board. See Fig. 5-5. b. Set the CH 1 POSITION control fu lly counter­ clockwise and the Sweep MODE to AUTO . c. Turn the INTENSITY control fu lly clockwise. d. Measure and note the maximum voltage level that can be attained w ith the IN TEN SITY control fu lly clockwise. e. Reduce the setting of the INTENSITY control to a level 70 volts below the maximum level measured in step d. f. Set the T IM E /D IV switch to 5 s/DIV and CH 1 POSI­ TIO N control to midrange. s c. a u T t t ! N < To avoid possible damage to the CRT phosphor, do n o t allow a bright spot to remain stationary fo r an extended period o f time. *V AQJA 1STi—ORT. 'Trirl.Ri^s^^ctvjrstm rat.RPfKL^jeeTig. 5-5) so the spot on the CRT just disappears. h. Set the T IM E /D IV switch to 1 ms and increase the IN TEN SITY control setting to obtain a visible display of nominal intensity. i. Obtain a stable display on the test oscilloscope of the unblanking waveform present at test point TP924. j. CHECK—Test oscilloscope display fo r optim um wave- .for.m. riset.ijne„and.fiat.tpo. <8> 5-8

risetime and fla t top. a. Set the Sweep MODE to SINGLE SWEEP. 1. Disconnect all test equipment. b. Connect the minus lead of a DC voltmeter to test point TP 1236 and the plus lead of the meter to test point TP1294. See Fig. 5-6 for test point locations. 6. Adjust Focus Range and Astigmatism a. Connect the PROBE C AL 0.6 V 1 kHz signal to the CH 1 input connector. c. A djust R 1293 (CE-1, see Fig. 5-6) fo r a meter reading of 100 volts. b. Adjust the TRIGGER LEVEL control for a stable display and advance the INTENSITY control to a com fort­ able viewing level. d. Move the plus lead of the meter to test point TP1296 (see Fig. 5-6). c. CHECK—CRT display fo r optim um focus of both the horizontal and vertical portions of the square wave. The e. Adjust R1295 (CE-2) for a meter reading of 100 volts. display should remain in focus as the setting of the IN TEN SITY control is varied. f. Move the plus lead of the meter to test point TP 1235. d. ADJUST—Focus Range adjust R968 (see Fig. 5-5) and ASTIG adjust R85 (located on rear panel) for optimum focus of both the horizontal and vertical portions of the g. Adjust Upper Non-Store Level R1224 for a meter reading of 90 volts. display. h. Set the UPPER SCREEN STORE button to the STORE (button in) position. e. Disconnect the PROBE C AL 0.6 V 1 kHz signal from the CH 1 input connector. 7. Adjust Trace Rotation i. Adjust Upper Store Level adjustment R1226 for a meter reading of 180 volts. a. Position the free-running trace to the center hori­ zontal graticule line. j. Set the UPPER SCREEN STORE button to non-store (button out) position and move the plus lead of the meter to test point TP1285 (see Fig. 5-6). b. CHECK—The trace should be parallel w ith the center horizontal line. k. Adjust Lower Non-Store Level R1274 for a meter reading o f 90 volts. c. A D JU S T -T R A C E ROTATION adjustment R80 (located on rear panel) so the trace is parallel w ith the horizontal graticule lines. 1. Set the LOWER SCREEN STORE button to the STORE (button in) position. 8. Pre-Set Collimation and Storage Target Levels NOTE m. Adjust Lower Store Level R1276 for a meter reading of 180 volts. I f C RT storage performance has been satisfactory, no adjustment o f the storage circuitry is necessary. 9. Adjust Upper and Lower Non-Store Levels Proceed with step 13. I f it is desired to touch up storage calibration to improve operation o f an instru­ m ent, proceed with step 9. I f this calibration procedure is being perform ed on an instrum ent a. Set the Sweep MODE to AUTO and the UPPER SCREEN STORE to STORE (button in). having unknown storage circu itry calibration (such as after replacing a CRT), continue with step 8. b. Adjust the INTENSITY control for a moderately bright trace. 5-9 5-9

pMlHW|-__ All ftigh?s ftf'> G eo m etry B 1292 SSeM PwHIBBB6 L o w e r S tore | Level “ R1276 1 Lo w e r N on- j S tore Level I U pper S tore Level R 122 6 U pper N on- S tore Level R 122 4 Fig. 5-6. L o c a tio n o f storage c irc u it ad ju stm en ts and test p o in ts. c. F ully w rite the entire screen by vertically positioning the trace from one extreme to the other. d. Set the LOWER SCREEN STORE button to the non­ store (button out) position. e. CHECK—The stored display in the Lower Screen area disappears very quickly and does not linger. Also should have m inim um "scalloping" of the Upper Screen stored display. f. AD JU S T—Lower Screen Non-Store Level R1274 fo r best non-store display compromise as described in step e. g. Set the LOWER SCREEN STORE button to STORE (button in). h. Fully w rite the entire screen by vertically positioning the trace from one extreme to the other. i. Set the UPPER SCREEN STORE button to the non­ store (button out) position. j. C H EC K—The stored display in the Upper Screen area disappears very quickly and does not linger. Also should have m inim um "scalloping" of the Lower Screen stored display. k. A D JU S T—Upper Screen Non-Store Level R1224 for best non-store display compromise as described in step k. 10. A djust Upper and Lower Store Levels N O TE Some compromises in the C R T display can be made b y adjusting the Store Level controls. When the operating level is increased, the brightness and w riting speed increase; however, the contrast ratio decreases. When the operating level is decreased, the contrast ratio increases; however, brightness and w riting speed decreases. a. Set both STORE buttons to their Non-store (button out) positions and adjust the IN TE N S ITY control for norm al display brightness. 5-10

defined trace. c. Set both STORE buttons to their STORE (button in) position, the TRIGGER SOURCE to LIN E, the TRIGGER LEVEL to midrange, and the T IM E /D IV to 1 ms/div. d. Connect the plus lead of the DC voltmeter to test point TP 1235 (see Fig. 5-6). e. Locate the w riting threshold in the follow ing manner: 1. Vertically position the trace from one extreme of the display area to the other in such a manner so as to achieve approximately three w ritten lines per division. 2. Carefully check the w ritten lines fo r breaks or gaps of 0.025 inch or more. If no breaks or gaps are evident after 10 seconds, note the voltmeter reading, then adjust Upper Store Level R1226 to decrease the operating level by 5 volts. 3. Erase the display, w ait 10 seconds, then write again and check for breaks or gaps. 4. Repeat this procedure of decreasing the operating voltage in 5-volt steps until breaks of approximately 0.025 inch occur. This is the w riting threshold. Note this voltage and rotate the Upper Store Level adjustment until the original level in step 2 is reached. NOTE Do n o t change the IN TE N S ITY or ASTIG M ATISM con trol settings. f. Locate the upper w riting lim it as follows: 1. Vertically position the trace from one extreme of the display area to the other in such a manner so as to achieve approximately three w ritten lines per division. 2. Carefully check the stored lines fo r more than normal trace spreading or background fadeup. If no trace spreading or background fadeup is evident after 10 seconds, adjust Upper Store Level R1226 to increase the operating level by 5 volts. 3. Erase the display, w ait 10 seconds, then write again and check for breaks or gaps. 4. Repeat this procedure until trace spreading or background fade-up occurs. This is the upper w riting lim it. Note this voltage. g. Adjust Upper Store Level R1226 fo r an operating point midway between the w riting threshold and the upper w riting lim it. Adjust Lower Store Level R1224 to set the lower screen operating level to the same point while measuring the voltage level at test point TP1285. It is desirable to have both storage targets at the same operating level to minimize the difference in background illum ina­ tion. h. Disconnect the DC voltmeter. i. IN TER A C TIO N —Collim ation is affected if change in operating level is significant. 11. Adjust Collimation a. Set the Sweep MODE to AUTO , the TRIGGER LE VEL control fu lly clockwise, and vertically position the free-running trace from one extreme of the display area to the other to w rite the entire screen. b. Rotate the INTENSITY control fu lly counter­ clockwise. c. ADJUST—R 1293 (CE-1) throughout its range. Note that as the adjustment is rotated in the clockwise direction, the display grows brighter in the center and then the bright­ ness spreads to the edges of the screen. A further increase in the voltage level at the CE-1 electrode w ill cause slight shadows to occur and then a large bright area in the center. Norm ally, the optim um setting for CE-1 is where the fu ll screen is bright but the shadows haven't yet started to occur. d. ADJUST—R 1295 (CE-2) throughout its range. Note that as the voltage level at test point TP1296 is increased, the edges of the display area brighten and then merge w ith the rest of the display. Norm ally the optim um setting fo r CE-2 is where the bright edges have merged and the display area is of uniform brightness. e. Erase the display and disconnect all test equipment. f. I NT E R A C T I O N —May affect operating level if changes in collim ation settings are significant. 12. Check Stored Writing Speed a. Set both STORE buttons to the Non-store (button out) position and the TRIGGER SOURCE to CH 1. 5-11

CH 1 input connector via a 42-inch 50 !T2 BNC cable. p. Adjust the IN TEN SITY control until the spot is just extinguished. c. Set the Time-Mark Generator for an output of 10 microsecond markers. q. Erase the display, w ait at least 3 seconds, then push the RESET button. Repeat this procedure while adjusting the ENHANCE LEVEL control to obtain a stored display where the background just starts to fade up. d. Adjust the TRIGGER LEVEL control fo r a stable display. e. Set the T IM E /D IV switch and the T IM E /D IV Variable control for one marker per division. r. CHECK—CRT stored display for no breaks or gaps exceeding 0.025 inch. Check the entire storage display area. Proper storage of a 2.5 ps/division sweep indicates an enhanced storage w riting speed of at least 400 centimeters per millisecond. f. Set CH 1 input coupling to GND. g. Position the trace on screen w ith the beginning of the trace at the left edge of the graticule. s. Set the STORE buttons to Non-store (buttons out), ENHANCE buttons to O ff (buttons out), Sweep MODE to AUTO , TRIGGER SOURCE to CH 1, and INTENSITY control fo r normal display intensity. h. Set the Sweep MODE to SINGLE SWEEP, the TRIGGER SOURCE to LINE, and both STORE buttons to the STORE (button in) position. 13. Adjust Geometry a. Set the CH 1 input coupling to DC. i. Adjust the IN TEN SITY control until the spot is just extinguished. b. A pply 1 ms and .1 ms tim e marks from the Time- Mark Generator to the CH 1 input connector. j. Press both ERASE buttons, w ait 10 seconds, and then press the RESET button. A single sweep should be pre­ sented and stored. c. Adjust the CH 1 POSITION control and the CH 1 V O LTS /D IV switch so the time marks extend above and below the vertical extremes of the CRT viewing area. k. CHECK—CRT stored display fo r no breaks or gaps exceeding 0.025 inch. Check the entire storage display area. Proper storage of a 10 ps/division sweep indicates a storage w riting rate o f at least 100 centimeters per millisecond. d. Adjust the TRIGGER LEVEL control fo r a stable display w ith the T IM E /D IV switch set to 1 ms. e. CHECK—CRT display for no more than 0.1 division of bowing or tilt of tim e marks in the center 6 X 1 0 division area, and no more than 0.2 division of misalignment in the 1. Erase the display, reduce the setting of the IN TEN ­ SITY control, and set CH 1 input coupling to DC. extreme upper and lower 1 X 1 0 division areas. m. Set the Sweep MODE to AUTO , the STORE buttons to Non-Store (button out), and TRIGGER SOURCE to CH 1. f. ADJUST—Geometry adjustments R967 and R1292 (see Figs 5-5 and 5-6) fo r minim um bowing and tilt of time marks. Norm ally, the optim um adjustment point of R1292 is fo r a voltage measurement of +230 volts at the em itter of transistor Q1292 located on the Storage circuit board. n. Set the T IM E /D IV switch and the T IM E /D IV Variable control for one marker per four divisions. g. Disconnect all test equipment. 14. Check BEAM FINDER Operation o. Set the CH 1 input coupling to GND, Sweep MODE to S IN G LE SWEEP, TRIGGER SOURCE to LINE, TR IG G ER LE VE L to midrange, STORE buttons to STORE (button in), and ENHANCE buttons On (buttons in). a. Press the BEAM FINDER button. b. Rotate the CH 1 POSITION and horizontal POSI­ TIO N controls fu lly clockwise and then fu lly counter­ clockwise. 5-12

running trace out of the graticule area when holding the BEAM FINDER button in. 15. Check External Z Axis Operation a. Connect the output of the Medium-Frequency Constant-Amplitude Signal Generator to the EXT TRIG and Z AXIS input connectors via a 50 £2 term ination, a BNC T, and tw o 42-inch 50 £2 BNC cables. b. Adjust the Constant—Am plitude Signal Generator for a 5-volt output amplitude of 50 kilohertz reference signal. c. Set the T IM E /D IV switch to 20 jus and the TRIGGER SOURCE to EXT. d. Adjust the TRIGGER LEVEL control for a stable display. e. CHECK—CRT display fo r noticeable intensity m odu­ lation of the trace (may require reducing the setting of the IN TEN SITY control). f. Increase the output frequency of the Constant Am plitude Signal Generator to 20 megahertz. g. Set the T IM E /D IV switch to .05 jus. h. CHECK—CRT display for noticeable intensity modu­ lation o f the trace. i. Disconnect all test equipment. 16. Check Chopped Operation a. Set the T IM E /D IV switch to 2 jus and the TRIGGER SOURCE to COMP. b. A pply 1 jus tim e marks to the CH 1 in p u t connector. c. Adjust the TRIGGER LE VE L control for a stable display. d. Adjust the T IM E /D IV switch and the Variable T IM E / DIV control fo r exactly tw o markers per division. e. Disconnect the Time-Mark Generator. Do not change the setting of the T IM E /D IV switch or the Variable T IM E / D IV control. f. Set the Vertical Mode to CHOP. g. Adjust the TRIGGER LEVEL control fo r a stable display. h. Adjust the CH 1 and CH 2 POSITION controls to separate the tw o traces. i. CHECK—Tim e duration of chopped waveform should be approximately 4.2 to 6.2 divisions (80 kilohertz to 120 kilohertz, approxim ately). NOTES

Equipment Required 1. Standard Am plitude Calibrator 7. Adapter (GR874 and BNC female connectors) 2. Square-Wave Generator 8. 50 £2 BNC Term ination 3. M e d iu m -F re q u e n c y Constant-Amplitude Signal 9. BNC T Connector Generator 10. 3-Inch Screwdriver 4. 24 pF Input Normalizer 11. Low-Capacitance Screwdriver 5. 42-Inch 50 £2 BNC Cable (2 required) 12. Tuning Tool 6. BNC 50 £2 10X Attenuator Control Settings Preset the instrum ent controls to the settings given under Preliminary Control Settings except as follows: Sweep MODE INTENSITY Input Coupling TRIGGER LEVEL AUTO For visible display GND Fully clockwise 17. Adjust Channel 1 Balance a. Change the CH 1 V O LTS /D IV switch from 10 mV to 1 mV. b. CHECK—CRT display for not more than 0.1 division of trace shift when switching from 10 mV to 1 mV. Channel 1 Variable Balance Adjust R212 Channel 2 Variable Balance Adjust R312 Inve rt Balance A d ju s t R348 ao«c . - -- Fig. 5-7. Lo cation o f Channel 1 and 2 balance adjustm ents. c. A D JU S T-C H 1 STEP ATTEN BAL adjustment (located on fro n t panel) for minim um trace shift when switching from 10 mV to 1 mV. d. Set the CH 1 V O LTS /D IV switch to 10 mV. e. Rotate the CH 1 Variable V O LTS /D IV control. f. CHECK—CRT display fo r not more than 0.2 division of trace shift when rotating the CH 1 Variable V O LTS /D IV control. g. ADJUST—Variable Balance adjust R212 (see Fig. 5-7) for m inim um trace shift when rotating the CH 1 Variable V O LTS /D IV control. h. Set the CH 1 V O LTS /D IV switch to 10 mV and the CH 1 Variable V O LTS /D IV control to CAL. 18. Adjust Channel 2 Balance a. Set the Vertical Mode to CH 2. b. Change the CH 2 V O LTS /D IV switch from 10 mV to 1 mV. c. CHECK—CRT display for not more than 0.1 division of trace shift when switching from 10 mV to 1 mV. d. A D JU S T-C H 2 STEP ATTEN BAL adjustment (located on fro n t panel) for minim um trace shift when switching from 10 mV to 1 mV. <§> 5-14

f. Rotate the CH 2 Variable V O LTS /D IV control. g. CHECK—CRT display for not more than 0.2 division of trace shift when rotating the CH 2 Variable V O LTS /D IV control. h. ADJUST—Variable Balance adjust R312 (see Fig. 5-7) for minim um trace shift when rotating the CH 2 Variable V O LTS /D IV control. i. Set the CH 2 V O LTS /D IV switch to 10 m V and the CH 2 Variable V O LTS /D IV control to CAL. j. Position the free-running trace to the center hori­ zontal graticule line. k. Set the IN VER T switch to the IN VER T position (button out). I. CHECK—CRT display fo r not more than 0.2 division of trace shift when inverting the Channel 2 display. m. ADJUST—Invert Balance adjustment R348 (see Fig. 5-7) for minim um trace shift when inverting the Channel 2 display. n. Push the IN VER T button in. 19. Adjust CH 1 and CH 2 GAIN a. Set input coupling fo r both channels to DC. b. Connect the output of the Standard Am plitude Cali­ brator to the CH 2 input connector via a 42-inch BNC cable. c. Set the Standard Am plitude Calibrator for a 50 m illi­ volt signal output amplitude. d. CHECK—CRT display fo r 5 divisions, ±0.15 division of deflection. e. ADJUST—CH 2 GAIN adjustment (located on fro n t panel) for exactly 5 divisions of deflection. f. Change Vertical Mode to CH 1. g. Remove the Standard Am plitude Calibrator signal from the CH 2 input connector and connect it to the CH 1 input connector. h. CHECK—CRT display fo r 5 divisions, ±0.15 division of deflection. i. ADJUST—CH 1 GAIN adjustment (located on fro n t panel) fo r exactly 5 divisions of deflection. 20. Check CH 1 Variable VO LTS/D IV Range and Attenuator Accuracy a. W ith exactly a 5-division amplitude display, rotate the CH 1 Variable V O LTS /D IV control. b. CHECK—CRT display can be reduced in amplitude to tw o divisions or less. c. Set the CH 1 Variable V O LTS /D IV control to CAL. d. CHECK—Using the CH 1 V O LTS /D IV switch and the Standard Am plitude Calibrator settings given in Table 5-1, check to see if the vertical deflection factor accuracy for each position o f the CH 1 V O LTS /D IV switch is w ithin 3%. TABLE 5-1 Vertical Deflection Accuracy V O LTS /D IV Switch Setting Standard Am plitude Calibrator O utput Vertical Deflection in Divisions Maximum Error For +3% Accuracy 1 mV 5 m illivolts 5 ±0.15 division 2 mV 10 m illivolts 5 ±0.15 division 5 mV 20 m illivolts 4 ±0.12 division 10 mV 50 m illivolts 5 Previously set in step 19. 20 mV 0.1 volt 5 ±0.15 division 50 mV 0.2 volt 4 ±0.12 division .1 V 0.5 volt 5 ±0.15 division .2 V 1 volt 5 ±0.15 division .5 V 2 volts 4 ±0.12 division 1 V 5 volts 5 ±0.15 division 2 V 10 volts 5 ±0.15 division 5 V 20 volts 4 ±0.12 division 10 V 50 volts 5 ±0.15 division 5-15

Attenuator Accuracy a. Remove the Standard Am plitude Calibrator signal from the CH 1 input connector and connect it to the CH 2 input connector and set the Vertical Mode to CH 2. b. W ith the CH 2 V O LTS /D IV switch set to 10 mV, set the Standard Am plitude Calibrator for a 50 m illivo lt output signal amplitude. c. W ith an exactly 5-division amplitude display, rotate the CH 2 Variable V O LTS /D IV control. d. CHECK—CRT display can be reduced in amplitude to tw o divisions or less. e. Set the CH 2 Variable V O LTS /D IV control to CAL. f. CHECK—Using the CH 2 V O LTS /D IV switch and the Standard Am plitude Calibrator settings given in Table 5-1, check to see if the vertical deflection factor accuracy for each position of the CH 2 V O LTS /D IV switch is w ithin 3%. 22. Check ADD Mode Operation a. A pply the Standard Am plitude Calibrator output signal to both the CH 1 and CH 2 input connectors via a BNC T and tw o 42-inch 50 SI BNC cables. b. Set both V O LTS /D IV switches to .1 V and the Ver­ tical Mode to ADD. c. Set the Standard Am plitude Calibrator fo r a .2 volt output signal. d. CHECK—CRT display fo r 4 divisions, ±0.12 division of deflection. e. Disconnect all test equipment. 23. Adjust Channel 1 V O LTS/D IV Switch Com­ pensation a. Set the Channel 1 V O LTS /D IV switch to 10 mV, the Vertical Mode to CH 1, and the CH 1 Input Coupling to DC. b. Connect the high-amplitude output of the Square- Wave Generator (Type 106) to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 SI BNC cable, a 50 SI BNC 10X attenuator, a 50 SI BNC term ination, and a 24 picofarad input normalizer. c. Adjust the output of the Square-Wave Generator fo r a display five divisions in amplitude and a repetition rate of one kilohertz. d. Adjust the TRIGGER LEVEL control fo r a stable display. e. C H E C K -C R T display at each Channel 1 V O LTS /D IV switch position for optim um square corner and fla t top. Typically less than +2%, —2%, or a total of 2% peak to peak aberration (+3%, —3%, or total of 3% peak to peak if the measurement is being made outside of the +20°C to +30°C temperature range). Remove the 10X attenuator and the 50 £2 BNC term ination as necessary to maintain a five-division display amplitude. f. ADJUST—Channel 1 V O LTS /D IV switch compensa­ tion as given in Table 5-2. Adjust fo r optim um square corner and fla t top. Remove the 10X attenuator and 50 £2 BNC term ination as necessary to maintain a five-division display amplitude. Fig. 5-8 shows the location of the variable compensation adjustments. TABLE 5-2 V O LT S /D IV Switch Compensation V O LTS /D IV Switch Setting Attenuator Adjusted fo r optimum Compensated Square Corner Flat Top 10 mV ±1 C9 for Channel 1 C19 for Channel 2 5 mV Check If error is greater than 2%, com prom ise setting at 1 mV, 2 mV, 5 m V, and 10 m V f o r b e s t o v e ra ll response. 2 mV Check 1 mV Check 20 mV -±2 C l 06 | C l07 50 mV ±■5 C110 j C111 .1 v ±10 C l 14 C l 15 Remove external 10X attenuator from generator .2 V Check If error is greater than 2%, compromise setting at .1 V, .2 V, and .5 V fo r best over­ all response. .5 V Check Remove 50 SI term ination 1 V ±100 C l 18 C l 19 2 V Check If error is greater than 2%, 5 V Check compromise setting at 1 V, 2 V, 5 V, and 10 V fo r best overall response. 10 V Check 5-16

24. Adjust Channel 2 V O LT S /D IV Switch Com­ pensation a. Set the Channel 2 V O L T S /D IV switch to 10 m V , the Vertical Mode to CH 2, and the CH 2 Input Coupling to DC. b. Connect the high-am plitude o u tp u t o f the Square- Wave Generator (Type 106) to the CH 2 input connector via a GR to BNC adapter, a 42-inch 50 £2 BNC cable, a 50 £2 BNC 10X attenuator, a 50 £2 BNC term ination, and a 24 picofarad input norm alizer. c. A djust the o u tp u t o f the Square-Wave Generator fo r a display five divisions in am plitude and a repetition rate of one kilohertz. d. CHECK—CRT display at each Channel 2 V O LT S / D IV switch position fo r optim um square corner and fla t top. T ypically less than +2%, —2%, total of 2% peak to peak aberration (+3%, —3%, total o f 3% peak to peak if the measurement is being made outside of the +20° C to +30°C tem perature range). Remove the 10X attenuator and the 50 £2 BNC term ination as necessary to m aintain a five division display am plitude. e. A D JU S T—Channel 2 V O L T S /D IV switch compensa­ tion as given in Table 5-2. A djust fo r optim um square corner and fla t top. Remove the 10X attenuator and 50 £2 BNC term ination as necessary to m aintain a five-division display am plitude. Fig. 5-8 shows the location of the variable compensation adjustments. f. Disconnect all test equipm ent. 25. A djust High Frequency Compensation a. Connect the positive-going fast-rise o u tp u t of the Square-Wave Generator (Type 106) to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 £2 BNC cable, and a 50 £2 BNC term ination. b. Set the Vertical Mode to CH 1 and both V O L T S /D IV switches to 10 m V. c. Set the Square-Wave Generator fo r a six-division display w ith a repetition rate o f 100 kilohertz. d. A djust the TR IG G ER LE V E L control fo r a stable display. 5-17

w ith the CH 1 POSITION control. f. CHECK—CRT display for optim um risetime w ith aberrations typically less than +2%, —2%, a total of 2% peak to peak (+3%, —3%, total of 3% peak to peak if this measurement is being made outside of the +20°C to +30°C temperature range). g. ADJUST—C217, C226, C461, R461, C572, L533, and L584 (see Fig. 5-9) fo r optim um risetime and aberra­ tions typically less than +2%, —2%, or a total of 2% peak to peak (+3%, —3%, a total of 3% peak to peak if this measure­ ment is being made outside of the +20°C to +30°C temperature range). h. Position the top of the display to the bottom grat­ icule line. i. CHECK—CRT display for aberrations typically less then +4%, —4%, or a total of 6% peak to peak. NOTE The tolerances given in steps i, o, t, and w apply only in the temperature range o f +20°C to +30°C. j. Remove the Square-Wave Generator signal from the CH 1 input connector and connect it to the CH 2 input connector. k. Set Vertical Mode to CH 2 and vertically center the display w ith the CH 2 POSITION control. I. CHECK—CRT display fo r optim um risetime w ith aberrations typically less than +2%, —2%, or a total of 2% peak to peak (+3%, —3%, or a total of 3% peak to peak if this measurement is being made outside of the +20 C to +30°C temperature range). m. A D JU S T —C317 and C326 (see Fig, 5-9) for optim um risetime w ith aberrations typically less than +2%, —2%, or a total of 2% peak to peak (+3%, —3%, or a total o f 3% peak to peak if this measurement is being made outside of the +20° C to +30° C temperature range). 5-18 Fig. 5-9. Lo cation o f vertical system high-frequency com pensation adjustm ents.

cule line. o. CHECK—CRT display fo r aberrations typically less than +4%, —4%, or a total of 6% peak to peak. p. Connect the negative-going fast-rise output of the Square-Wave Generator to the CH 2 input connector. q. Adjust the Square-Wave Generator for a six division display. r. Set TRIGGER SLOPE to — and obtain a stable dis­ play. s. Position the bottom of the display to the top of the graticule. t. CHECK—CRT display fo r aberrations typically less then +4%. —4%, or a total of 6% peak to peak. u. Remove the Square-Wave Generator signal from the CH 2 input connector and connect it to the CH 1 input connector. v. Set the Vertical Mode to CH 1 and position the bottom of the display to the top of the graticule. w. CHECK—CRT display for aberrations typically less than +4%, —4%, or a total of 6% peak to peak. x. Reconnect the positive-going fast-rise output from the Square-Wave Generator to the CH 1 input connector and set the TRIGGER SLOPE switch to +. y. Set the CH 1 V O LTS /D IV switch to 5 mV. z. Adjust the Square-Wave Generator for a six-division display. aa. V ertically center the display using the CH 1 POSI­ TION control. ab. CHECK—CRT display in 1 m V, 2 m V, and 5 mV positions of the CH 1 and CH 2 V O LTS /D IV switches. Refer to Table 5-3. Use the 10X BNC attenuator as neces­ sary to maintain a six-division display amplitude. TABLE 5-3 Amplifier Compensation VOLTS/DIV Switch Setting Compensation Adjustment Typical Aberration 5 mV C225 in Channel 1 C325 in Channel 2 Less th a n +2%, -2 % , total of 2% peak to peak. 2 mV C223 in Channel 1 C323 in Channel 2 1 mV C220 in Channel 1 C320 in Channel 2 Less th a n +3%, -3 % , total of 3% peak to peak. ac. ADJUST—Refer to Table 5-3 fo r the correct adjust­ ment and tolerances. See Fig. 5-9 for adjustment locations. ad. Disconnect all test equipment. 26. Check Vertical A m plifier Bandwidth a. Connect the output of the Medium-Frequency Constant-Am plitude Signal Generator to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 Ei BNC cable, a 10X BNC attenuator, and a 50 £2 BNC term ination. b. Set both V O LTS /D IV switches to 10 mV, the Ver­ tical Mode to CH 1, and the TRIGGER LEVEL control fu lly clockwise. c. Adjust the signal generator output amplitude for a six-division display of the 50 kilohertz reference frequency. d. W ithout changing the output amplitude, increase the output frequency until the display is reduced to 4.2 divi­ sions. e. CHECK—O utput frequency of the signal generator must be at least 25 megahertz. f. Repeat this bandwidth check procedure for all posi­ tions listed in Table 5-4. Check both Channel 1 and Channel 2. ® 5-19

VOLTS/DIV Minimum Switch Setting Bandwidth — 15; C to +30°C +30°C to +55°C 10 mV 25 megahertz 25 megahertz 5 mV 23 megahertz 21 megahertz 2 mV 20 megahertz 18 megahertz 1 mV 18 megahertz 16 megahertz 27. Check 5 MHz BW Bandwidth a. Connect the output of the Medium-Frequency Constant-Amplitude Signal Generator to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 H BNC cable, and a 50 £1 BNC termination. b. Set the CH 1 VOLTS/DIV switch to 10 mV and the Vertical Mode to CH 1. c. Set the 5 MHz BW button to the out position. d. Adjust the output of the signal generator for a six- division display of the 50 kilohertz reference frequency. e. W ithout changing the output amplitude, increase the frequency of the signal generator until the display is reduced to 4.2 divisions. f. CHECK—Output frequency of the generator must be 5 megahertz, +1 megahertz. g. Disconnect all test equipment. NOTES

Equipment Required 1. Med i u m -F requ ency Constant-Amplitude Signal 4. BNC T Connector Generator 5. 42-Inch 50 f t BNC Cable (two required) 2. Low-Frequency Signal Generator 6. 3-Inch Screwdriver 3. 50 f t BNC Termination Control Settings Preset the instrument controls to the settings given under Preliminary Control Settings except as follows: Sweep MODE AUTO TIM E/D1V 50 ms IN TEN SITY Visible Display 28. Adjust Trigger Level Centering a. Connect the output of the Medium-Frequency Constant-Am plitude Signal Generator to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 f t BNC cable, and a 50 f t BNC term ination. b. Adjust the output of the signal generator fo r a 0.3- division display of the 50 kilohertz reference frequency. c. Vertically center the display around the center Fig. 5-10. Lo cation o f Trigger Level C entering adjustm ent, graticule line. d. C H E C K -W ith the TRIGGER LEVEL control centered, should have a stable display in the + and — posi­ tions of the TR IGGER SLOPE switch. e. ADJUST—Trigger Level Centering adjustment R629 (see Fig, 5-10) fo r a stable display in both the + and — positions of the TRIGGER SLOPE switch. 29. Adjust CH 1 and COMP Trigger DC Level a. Set the TRIGGER COUPLING to DC and the TR IGGER SLOPE switch to +. b. CHECK—CRT fo r a stable display. c. ADJUST—Comp Trigger DC Level adjustment R274 (see Fig. 5-11) fo r a stable display. 5-21 Fig. 5-11. Lo cation o f trigger DC level adjustm ents.

Calibration—434 e. CHECK—CRT for a stable display. f. ADJUST—CH 1 Trigger DC Level adjustment R284 (see Fig. 5-11) for a stable display. 30. Check Trigger Circuit Operation a. Connect the signal from the signal generator to the CH 1 input connector via a GR to BNC adapter, a 42-inch 50 12 BIMC cable, and a BNC T connector. Connect the unused output of the BNC T connector to the EXT TRIG input connector via a 42-inch 50 12 BNC cable and a 50 12 BNC term ination. b. CHECK—Stable display can be obtained using the signal amplitude and coupling modes given in Table 5-5. TABLE 5-5 Trigger Operation Check TRIGGER SOURCE TRIGGER COUPLING M inim um Signal Am plitude 5 MHz 25 MHz CH 1 & COMP AC DC LF REJ 0.3 div 1 div EXT AC DC LF REJ 35 mV 125 mV c. Set TRIGGER SOURCE to COMP and TRIGGER COUPLING to HF REJ. d. Adjust the signal generator output for a one-division display of the 50 kilohertz reference frequency. e. CHECK—A stable display can be obtained. f. Adjust the signal generator output for a one-division display of a 1 megahertz signal. g. CHECK—A stable display can not be obtained. h. Replace the Medium-Frequency Constant-Amplitude Signal Generator w ith a Low-Frequency Signal Generator and remove the 50 12 BNC term ination from the test setup (42-inch 50 12 BNC cable should be connected directly to the EXT TR IG input connector). i. Set the TRIGGER COUPLING to LF REJ. j. Adjust the Low-Frequency Signal Generator for a one-division display of a 30 kilohertz signal. k. CHECK—A stable display can be obtained. I. Adjust the signal generator for a one-division display of a 100 hertz signal. m. CHECK—A stable display can not be obtained. n. Adjust the signal generator for a one-division display of a 100 kilohertz signal. o. Set Sweep MODE to NORM. p. CHECK—Should be able to obtain a stable display. When the TRIGGER LEVEL control is rotated fu lly counterclockwise or clockwise, there should be no display presented on the CRT. 31. Check Single Sweep Operation a. Adjust the signal generator for a 0.3-division display of a 1 kilohertz signal. b. Set the TRIGGER COUPLING to AC. c. Adjust the TRIGGER LEVEL control for a stable display. d. Set the Sweep MODE to SINGLE SWEEP. e. Press the RESET button. f. CHECK—A single-sweep display (one sweep only) is presented. g. Rotate the TRIGGER LEVEL control fu lly clock­ wise. 5-22