AT&T M9B Description And Application Manual

BELL SYSTEM PRACTICES Plant Series SECTION 100-513-101 Issue 1, April, 1946 AT&TCo Standard M9B METER (PORT ABLE VOLT-OHM-MILLIAMMETER DESCRIPTION AND APPLICATION CONTENTS 1. GENERAL . . . . . 2. CIRCUIT AND EQUIPMENT FEATURES . . (A) M9B Meter. . . . . . . . . . . (B) Test Leads, Carrying Strap, and Carrying Case . . . . . . 3. OPERATION , . . . . . (A) Precautions . . . . (B) Preparation. . . . . . . . (C) Scales . . . . . . . . (D) Voltage Measurements . . . . (E) Current Measurements (F) Resistance Measurements . (G) Capacitance Measurements 4. MAINTENANCE. . . . . . . . . . . . (A) Voltage Accuracy . . (B) Battery Replacement . . . . . . 5, REPAIR . . . . . . . . . . . . . . (A) General (B) Meter Unit . . . . . . . (C) Meter Glass and Zero Corrector (D) Pin Jacks • 6. REPLACEMENT PARTS 1. GENERAL . . . . . PAGE l 2 2 3 4 4 4 4 5 5 5 6 8 8 c . 9 9 10 10 11 12 1,01 This Section describes the Western Elec- tric Company M9B Meter (portable volt- ohm-milliammeter), includes instructions for its use and methods for replacement of parts. The information . is also generally applicable to the D-166852 Meter. 1,02 The M9B Meter is a small portable multi- meter designed for general maintenance use for the measurement of a-c and d-c volt- ages, d-c current, and resistance, Five volt- age scale ranges are provided, both a-c and d-'c, from 0-3 to 0-300 volts, with a sensitivity of 2000 ohms per volt on all scales. Three d-c current ranges are provided from 0-150 milli- amperes to 0-15 amperes, and four resistance measuring scale ranges from 0-1000 ohms to 0-1,000,000 ohms, 1.03 A special double-pointer meter movement provides unusual legibility of scales; the linear voltage and current scale markings are grouped in the upper semicircle of the me- ter fa~e, and the nonlinear resistance scale is located under the pointer sweep on the lower semicircle of the meter face, The wide angle sweep (150 degrees) of the pointer adds to the legibilityof the scales. A nonglare, hardened glass window is used. All circuit connections are made to positive contact pin jacks, Fig, 1 shows a face view of the M9B Meter. Fig. 1 - M9B Meter - !''ace View 1.04 The M9B Meter is furnished with a pair of KS-9290 test pick leads• a pair of KS-9291 test clip leads and a KS-9308 carrying strap. A 4-1/2-volt battery (par, 2.08) is required for use in the meter. The meter is equipped with "D" loops for attaching a neck carrying strap (KS-9308), A fibre carrying case (KS-9307) is available for carrying the meter and test leads. (See Figs. 2 and 3.) The M9B Meter is similar to the Western Electric Company D-166852 Vol~- ohm-milliammeter which was recently developed for maintenance use with carrier, central office~ and telegraph equipments. Copyright, 1946 1 by American Telephone and Telegraph Company Printed in U.S. A, Page 1

SECTION 100-513-101 2, CIRCUIT AND EQUIPMENT FEATURES (A) M9B Meter 2,01 A schematic of the M9B Meter is shown in Fig, 4, The scale ranges provided are as follows: Voltmeter Ranges A-C or D-C (2000 Ohms Per Volt) 0-3 volts 0-15 volts 0-30 volts 0-150 volts 0-300 volts Ammeter Ranges D-C Only 0-150 milliamp, 0-3 amp. 0-]6 amp. Ohmmeter Ranges 0-1000 ohms 0-10,000 ohms 0-100,000 ohms 0-),,000,000ohms The accuracy of the meter is _:!:2 per cent. of full scale for d-c and _:5 per cent, of full scale fora-c measurements; for resistance meas- urements, the accuracy is _:!:2 per cent. at one- half the pointer travel, i.e., at "4o" on the OHMS scale, 2.02 The meter movement is of a relatively sensitive type, requiring 100 microamperes of current to obtain full-scale deflection,and is combined with suitable series and shunting resistances to provide for the direct current, the a-c and d-c voltage, and the resistance ranges tabulated in Paragraph 2 ,01. In the voltmeter condition, on all scales, a-c and d-c, the internal resistance (sensitivity) of the meter is 2000 ohms per volt, 2,03 The dial (Fig. 5) is circular, with the current and voltage scales on the upper half of the dial and the nonlinear resistance scale on the lower half, The double-ended pointer is pivoted at the center. One end of the pointer travels over the upper scales; the other end of the pointer sweeps over the lower scale. This provides a complete separation of the nonuniform resistance measuring scale from the markings for the current and voltage meas- uring scales, which makes the scales easier to read than the conventional type meter which has all scales grouped under one pointer. The pointer swing is from zero on the left, to full scale on the right, on all scales, Instead of the conventional arc of 90 degrees, the point- ers swing through a 150-degree arc from zero to full-scale readings. The outside scales are approximately 2-374" long. 2,04 A face view of the volt-ohm-milliammeter is shown in Fig, 1. All the connections to the meter are made by means of pin ~acks, Connections for resistance measurements (X and R jacks) are on the left side of the panel; those for voltage measurements (V jacks) are located on the ril$ht side of the :{lanel and cur- rent measuring (A and MA jacks) are located along the lower part of the panel. Page 2 2,05 A copper-oxide rectifier in the meter provides means for using the d-c meter movement for measuring a-c voltage, Operation of the AC-DC toggle switch at the right of the meter dial cuts the rectifier into the circuit for a-c voltage measurements or eliminates it for all d-c measurements, including resistance. 2.06 Two toggle switches located to the right VM of the meter and designated AC-DC, and AM - RES, together set up the internal connec- tions which are required for each type of use; that is, as either an a-c or d-c voltmeter, as a d-c a:mmeter, or as a resistance measuring device. 2,07 A quick-acting push-to-read switch (with its push-button marked PRESS) is provided to connect the meter movement across the in- ternal d-c measuring shunts which are associ- ated with the -A, 15A, 3A, and 15011A jacks. The meter movement is only connected to read current while this switch is depressed, ,., Fig. 2 - 119B Meter in Carrying Case Open Cover

Fig, 3 - KS-9307 Carrying Case with KS-93()8 Carrying Strap 2.08 A 4-1/2-volt battery is required for use in the meter, The battery mounts in a bracket inside the meter case, Any one of the following batteries may be used: Bright Star 03-17s Eveready 781 Burgess 5360 Ray-0-Vac 531R Bond 317 2,09 The knob BATTERY ADJUS1'MENT controls a rheostat which adjusts the "zero" setting portion of the resistance measuring circuit, This setting varies with the voltage and condi- tion of the 4-1/2-volt dry cell battery, ISS 1, SECTION 100-513-101 (B) Test Leads, Carrying Strap, and Carrying Case 2,10 The tes~ leads supplied with . the meter are equipped with pin terminals at one end for connection to the meter jacks, One pair of test leads (KS-9291) is equipped at the other end with test picks, the other pair (KS-9290) with test clips, The test picks are 7-1/2" long and consist of a slender hard rub- ber handle with a pick extending approximately 1/2 11 from the end, The test clips are narrow, alligator-type clips. 2,11 The KS-9308 carrying strap is available for use with the M9B Meter. This strap (Figs, 2 and 3) is equipped on each end with a harness snap and is adjustable as to length by means of a sliding buckle, The strap is in- tended to attach to the metal 11D11 loop on the sides of the instrument, and to be used as a neck strap to support the meter so as to leave both hands of the tester free for making test connectionsJ or the strap may be attached to the KS-9307 carrying case and used in the same way, 2,12 The Ks-9307 carrying case maybe obtained for use with this meter, This fibre case (Figs. 2 and 3) i,s arranged with a hinged top, inside of which a snap-fastened fabric flap ~rovides a place for storing the test leads (Fig, 2), There is a "D" ring on each side of the case to which the KS-9308 carrying strap tnay be attached, The case is so designed that Bl x~•l•l1----..----..-----------------t------------l.'O -v 4.!>V, 32 . !I >--- ..... R4 299- 2994 ... R6 2000 ... 30,000'"' BATTERY ADJUSTMENT Pl R20 492 ... -A Rl7 0 I :.A Rl8 0 3A Vt.A AM Fig, 4 - Schematic Diagram of M9B Meter aircuit 4885"' 24,000- 120,000""' 150,000 Page 3

SECTION . 100-513-101 when the lid is open the meter can be used with- out removing it from the case. A simple clamp- ing device holds the meter securely in posi- tion in the case, cushioned between sponge rub- ber blocks on sides, end, and bottom, There is room for two spare dry batteries inside the carrying case, in the space between the hinged side of the case and the meter; one may be placed on each side of the meter clamping de- vice, 2,13 The dimensions and weights of the H9B Meter and associated equipment are as follows: Dimensions pn.) Wt, Name Length Width Depth Lbs, M9B Meter 8 4-1/4 3-1/2 3.25 KS-9290 Test Leads (pair) 50 0.18 (ea) KS-9291 (pair) Test Leads 50 (ea) 0.06 KS-9308 Carrying 4o 1 0.18 Strap KS-9307 Carrying 8-1/2 6 6 3.4 Case 3. OPERATION (A) Precautions 3.01 In order to avoid damage to the meter, the following precautions should be ob- served, Do not connect resistance measuring jacks (X and R) to a circuit which includes a source of either d-c or a-c power, since it may damage the meter movement and t he meter resistances, This is particularly important with regard to a-c power, because the alternat- ing current entering the meter throu~h the re- sistance measuring jacks (X .and R) will not give a meter deflection and therefore might destroy either the meter coil or a resistance without giving a warning indication on the me- ter. Do not connect the current measuring jacks (-A, 15A, 3A, and 150MA) to a circuit in which the current is greater than 15 amperes d-c; do·not connect into an a-c circuit, (B) Preparation 3,02 Before making direct current or a-c or d-c voltage measurements, check that the upper pointer of the meter lines up exactly with the zero mark of the upper scales, ( which also sets the lower pointer at the (infinity) nark of the resistance measuring scale), The zero posi~ion of the pointers can be adjusted by turnin g the slotted bakelite button in the center of the meter glass with a screwdriver or small coin. (C) Scales 3.03 Two scales, inner and outer, appear on the top half of the meter face. A single scale for resistance measuring, calibrated in ohms is on the lower half, Fi g , 5 shows the meter scales in detail. 3.04 The inner scale (with red markings) on the upper half of the dial is for readin g a-c voltages in the 0-3-volt range. This separate scale is necessarv because a nonuniform move- ment of the meter.pointer is produced when a-c voltage within this low range is measured, 3,05 The outer scale is used for all other voltage measure ;nents both a-c and d-c and for direct-current measurements, It haa 75 equal divisions with every fifth division a long mark, It is marked with black figures at each 25 divisions, as follows: 50 100 100 200 150 300 The outer scale divisions and markings have the fol l owing values for current and voltage measurements: Current or Voltage Value Scale Value for Top Pointer at Each Division When Connected 50 100 150 Short Long Measuring to Jacks 100 200 300 Lines Lines Direct -A and 150MA 0.050 amp. 0.100 amp, 0.150 amp, 0.002 amp, 0.010 amp, Curren+, -A and 3A 1.0 amp, 2,0 amp, 3.0 amp. o.o4 amp, 0.2 amp, -A and 15A 5.0 amp. 10.0 amp. 15.0 amp, 0.2 amp. 1.0 amp. Voltage* -V and -,v 1 volt 2 volts 3 volts 0,04 volt 0.2 volt D-C Only -V and 15V 5 volts 10 volts 15 volts 0.2 volt 1 volt Voltage -V and 30v 10 volts 20 volts 30 volts o.4 volt 2 volts A-C or -V and 150v 50 volts 100 volts 150 volts 2,0 volts 10 volts D-C -V and 300v 100 volts 200 volts 300 volts 4,o volts 20 volts Voltage• -V and ,v Use top pointer and RED scale A-C Only * For measuring a-o voltages when jacks, see Paragraph 3.04. connected to the -V and "3V Page 4

Fig. 5 - M9B !1eter - Face View 3.06 The resistance scale (lower half of the dial (Fig. 5)) is read directly in ohms if the test cords are connected to X and R (0-1000-ohm scale). If the test cords are con- nected at X and RxlO, the scale reading should be multiplied by ten; if the connections are at X and RxlOO multiply the scale reading by 100; if connections are at X and RxlOOO, multiply the scale reading by 1000. (D) Voltage Measurements 3.07 In measuring d-c voltage, set the upper toggle switch at its DC position; in measuring a-c voltage, set this switch at its AC position. Set the lower toggle switch at its X}1 position. Make connections to the -V pin Jack and to the 300v, 150v, 30v, 15v, or Yi pin jack depending on the amount of voltage to be measured. In measuring d-c voltage con- nect the -V pin jack to the negative side of the circuit being checked. (E) Current Measurements 3.08 Direct current onlt can be measured. When direct curren is to be measured set the upper toggle swit.ch at its DC position and the lower toggle switch at its m position, ISS 1, SECTION 100-513-101 Connect the negative side of the circuit to the -A pin jack and the positive side of the cir- cuit to the 15A, 3A, or 150MA jack dependint on the amount of current to be measured, Caution: amount current is nown, s art w1 t e jack, Current will flow through the meter shunts, but not throu~h the meter movement, as soon as connec ion throu~h these ~in jacks is made. Push down t e ~~~y button marked PRESS to read the meter, This ermits current to flow t roug e me movemen • e me- ter indication 1s less than 3 amperest connect to the 3A pin jack, and if i is less than 150 milliamperes, connect to the 150MA pin jack, (F) Resistance Measurements 3.09 When resistance is to be measured, set the ut*er toggle switch at its DC posi- tion, ande lower toggle switch at its RES position, Connect one test cord to the X pin jack, and the other test cord to either the R, RxlO, RxlOO, or RxlOOO jack depending on the value of the resistance to be measured. Short- circuit the test cords and turn the BATTERY ADJUSTMENT lmob until a zero reading is obtained on the ohms scale, This adjustment is necessary to calibrate the meter circuit to the exact voltage and condition of the dry-cell battery, When a zero adjustment can no longer be obtained within the range of the BATTERY ADJUSTMENT lmob, the battery of the meter is no l~nger in suitable condition and should be replaced (Paragraph 4.03). Connect the test cords to the circuit to be measured and read the resis- tance scale of the meter. 3.10 The resistance scale is not uniform, and the pointer moves farther for a particu- lar value of resistance change when over the left side of the scale than when over the right side of the scale. Therefore, greater accuracy of reading results when the scale is selected which as faras possible keeps the pointer near the middle range of its swing. The following table suggests the most favorable connections to the meter for various ranges of resistance values to be measured. Resistance - Ohms 0-200 100-2000 1000-20,000 10,000-1.000.000 Heter Jack Connections X and R X and RxlO X and RxlOO X and RxlOOO 3.11 When making resistance measurements the drain on the 4-1/2-volt test battery is dif'f'erent f'or connections to ea.ch pair of' jacks (i,e,, X and R, X and RxlO, X and RxlOO, or X and RxlOOO), This may, especially with a used Page 5

SECTION 100-513-101 battery, cause the zero setting to need a dif- ferent BATTERY ADJUSTMENT knob position for each resistance measuring 8Cale range, There- fore, when accuracy of the measurement is im- portant, it is desirable to check the zero set- ting (by short-circuiting the test leads) each time the scale connection to ~he meter jacks is changed, Also, when connected to the X and R jacks, the current drainis relatively heavy, and it may be desirable to recheck the zero setting from time to time while using this scale range, The meter is accurate for resis- tance measurements within +2 per cent, at mid- swing of the pointer, The current drains at zero reading on the ohms scale, for each test lead connection, are approximately as follows: Test Lead Connection Current - MilliamEeres X and R 129.5 X and Rxl0 12.95 X and Rxl00 1.3 X and Rxl000 0.13 3,12 If a 4,5-volt battery of a suitable size is not available, any 4,5-volt battery can be connected externally for making resis- tance measurements, If this external 4,5-volt battery differs appreciably as to its internal resistance, from the types of batteries normal- ly used in the meter• the accuracy of the lower resistance scales may be slightly decreased. 3.13 To use an external battery, connect the negative terminal of the battery to the -V terminal of the meter, Connect the positive terminal of the battery to one side of the cir- cuit whose resistance is to be measured. Con- nect the other side of the resistance to the proper pin jack for the scale required (Rxl0, Rxl00, or Rxl000), (G) CaEacitance Measurements 3,14 The following Paragraphs (3.15 through 3,21) cover the use of the M9B Meter for measuring capacitance by the ballistic kick method of testing. By this method, the meter may be used to make capacitance measurements within the limits of approximately 0.1 mf to 200 mf, with a reasonable degree of accuracy. 3,15 General :Method. In measuring capaci- tance, the resistance measuring portion of the M9B Meter circuit is used, with the test leads connected to the X and RxlO00 pin jacks for the lower capacitance values or to the X and Rxl00 pin jacks for higher values. The maximum swing of the pointer at the in- stant of connection to the capacitor is read on the 0-150 scale on the upper part of the meter dial. This scale reading is then con- verted into capacitance in microfarads by use 0£ the curves in Fig, 6 or 7, SeYeral repeti- tions of the swing generally are required for Page 6 2.0 1.9 I.& 1.7 I.& i.5 I 7 6 5 4 3 .2 .I c~Wi~"'""'- j AfTER ~ SHORT CIRCUIT I I l I I ' I I I I ,' I i ' / n· I /1,;' ~ -- :..-:: ) ,, / I J I " / ,/ [/ - i- ! ; h- CURVE 8 1 I SWING USING REV. SWITCH j I ~Y~"" J AFTER y SHORT CIRCUIT I I I I/ CURVE B\ SWING USING / REV. SWITCH ), .... _,...,~ - ·"" .... - 2 0 I 9 8 17 16 I 5 I I m 4o z 3 < < I 2"' ! II I I 0 .. ::E I 9 8 ~ ~ 7 ~ ,-- If, < u ... ... 5 4 3 2 I 0 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 METER DEfLtCTION ON 0-150 SCALE Fig. 6 - Capacitance Measurement - Smaller Values - Usin~ X and Rxl000 Jacks 20 19 ,e 17 16 15 1D 14 0 ~ 13 "' 12 .., ~I :, I y IO .. ~ 9 .., ~ II ~ u 7 It ~ 6 5 4 3 CURVE A'""' j &WING AFTER \f SHORT CIRCUIT I I . I I I ·' I I I I I I ' I IL' ' /I 1,.- I/ 2 J,..- L.,.,-• I ' CURVE Bl • I/ SWING ; USING REIi SWITCH I I j ' c~i~t-- AFTER \ j SHORT CIRCUIT I I I ) I/ J ,v V ,v ,,...,... .... - L,.• 1.-- i-- I ' I I j I CURVE 8\ SWING USING REV SWITCH ... ..... ..... I-- L>" 200 90 80 70 60 50 40 l1l 30 2 I I I I I I I I I I < 20 < "' 10 ~ a: :, 00 u I ,._ 90 :I! I 80 tf z ~ 70 V It 60 ~ 50 40 30 20 0 I 0 ~ 1::::: 0 0 10 20 30 40 50 60 70 &O 90 100 110 120 130 140 150 METER OEFLECTION ON 0-150 SCALE Fi~, 7 - Capacitance MeaGurement - Larger Values - Using X and Rxl00 Jacks

accurate reading, The test may be made by ei- ther of two methods; by -short-circuiting the capacitor to full? discharge it and then making connection to the meter; or, by reversing the polarity of the connections from the meter to the capacitor, without intermediate discharge of the capacitor, The latter method requires the use of an auxiliary switch inserted in the connections between the meter and capacitor as shown in Fig. 9. When the short-circuiting method is followed, no auxiliary switch is re- quired; however, if desired, a switch may be used in the test leads to discharge the capac- itor and then reconnect it to the meter, in order to simplify the procedure (see Fig. 8), The reversing switch method, covered in Para- graph 3. 18, should not be used for electrolytic capacitors, since a single polarity should be used v1hen testing this type of capacitor; that is, the(+) or X terminal of the meter should alv1a,rs connect to the ( +) terminal of the ce- pacitor. When using the reversing method, the magnitude of the pointer swing is approximately double that obtained after shorting the capac- itor. The dotted curves Band B• in Figs, 6 and 7 are provided for use when the reversing switch is employed, and solid curves A and A• when the short-circuiting switch is used, 3.16 The table below summarizes the connec- tions which may be used for various values of capacitance, and the curves which are appl~cable for the testing procedure used. The A' and B' curves in both Figs. 6 and 7 correspond to the lower portions of the A and B curves respectively, but are plotted on a larger scale for easier and more accurate reading of the smaller values of capacitance, It is therefore preferable to use curves A• or B• if the pointer swing is low enough to be read on them. 3.17 Electrolytic Capacitors. Before measur- ing the capacitance of electrolytic ca- pacitors which have not been in service for e.n extended period,the film should be restored by connecting the ce.paci tor to a d-c voltage ap- proximating the normal working voltage of the capacitor, in series with a lamp, for about 30 minutes, If a capacitor is tested in the cir- cuit, and there are any shunting paths around the capacitor, at lee.st one terminal should be discom1ected before proceeding. Capacitance Pin Jack Range Connectiors 0,1 to 2.0 mf X and Rxl000 2.0 to 20 mf (X and Rxl000 ( or (X and RxlO0 20 to 200 mf X and Rxl00 Fig, 6 6 7 7 155 1, SECTION 100-513-101 3.18 Procedure, The following procedure for measuring capacitance is to be followed when neither a sho~t-circuiting switch nor a reversing switch is to be used, r'hen a short- circuiting switch or a reversing switch is used, the procedure given below is modified as covered in Paragraph 3,20 or 3.21. (1) For higher capacitance measurements, use the X and Rxl00 pin jacksJ for lower capacitance measurements, use the X and Rxl000 pin jacks (see Paragraph 3.16). (2) Set the meter switches to their DC and RES positions, connect the test cords to the meter jacks to be used and adjust the setting of the BATTERY ADJUSTMENT knob for zero reading on the resistance scale (as covered in Para~raph 3.09), (3) Connect the test lead from the X pin jack to one terminal of the capacitor (if the capacitor is electrolytic, connect this lead to the positive terminal). (4) With the other test lead disconnected from the meter, connect its clip end to the other capacitor terminal (negative, if capacitor is electrolytic), (5) Then, quickly insertthe other terminal of this test lead into the Rxl00 or the Rxl000 pin jack, at the same time watching the meter needle to determine its maximwn swin~. If this oonneotion is not made quickly a full swing of the pointer will not be obtained, (6) Read the maximl.Ull swing on the 0-150 (upper) scale and convert the reading to microfarads by use of the solid curv~s A or A• in Fig, 6 or 7; use Fig. 6 for connections to the X and Rxl000 jacks; use Fig. 7 for X and Rxl00 connections. (7) To repeat the test, remove the lead from the meter Rxl00 or the Rxl000 jack, touch it to the capacitor to short- circuit and discharge it, then rel?eat the ~onnection to meter, as in Items (5) and (6) above. Aoolicable Curve Short Get, Rev. Sw, Method- Method- Solid Curve Dotted Curve A• B' A B A' B' A B Page 7

SECTION 100-513-101 SHORTING SWITCH TO X PIN JACK_+.._ ____ "° OF METER TO RXIOO OR _ RxlOOO PIN ----.-o JACK OF METER TO POSITIVE ------TERMINAL OF CAPACITOR TO NEGATIVE ------TERMINAL OF CAPACITOR Fig. 8 - Wiring of Shorting Switch 3.19 Procedure Using Short-circuiting Switch. For greater convenience in making capac- itance measurements, a switch may be used to short-circuit the terminals of the capacitor before each test. A quick-acting DPDT toggle switch may be used for this purpose, wired as shown in Fig, 8. After the switch is connected to the meter jacks and to the capacitor as in- dicated in Fig. 8, operate the switch quickly from its short-circuit position to charge the capacitor, the charging current producing the meter pointer swing; then restore the switch to its short-circuit position to discharge the capacitor. If repetition of the swinis is de- sired, it may be obtained by repeated opera- tion of the switch. Otherwise, the method de- scribed in Paragraph 3.18 is followed, using the solid curves (A or A1 ) in Fig. 6 or 7. TO + X PIN JACK------ .. OF METER TO RXIOO OR RXIOOO PIN------ JACK OF METER Fig. 9 - Wiring of Reversing Switch 3.20 Procedure Using Reversing Switch~ If desired, a reversing switch may be used with the test leads in place of the shorting switch described in Paragraph 3.19. Fig. 9 shows a snap-action double-pole double-throw toggle switch wired as a reversing switch and indicates the connections to the meter and to the capacitor. After these connections have been made, operation of the switch to either position reverses the polarity of the voltage applied to the capacitor by the meter and pro- duces a swing of the meter pointer. Repeti- tions of the swing maybe obtained by operating the switch back and forth until the maximum swing is ascertained, The reading obtained by this method is converted to mi_crofarads by us- ing the dotted curves ( B or B') in Fig. 6 or 7. Page 8 Since the effective change in voltage across the capacitor when using a reversing switch is twice that obtained when using the uni-polarity short-circuiting switch, the resulting swing of the pointer is approximately doubled for a given value of capacity. 3.21 Leaka e Resistance of Electrol ic Ca- paci ors. n measuring capaci ance as c6vered in the preceding paragraphs, the meter needle should return to O after the initial swing. In checking electrolytic capacitors, the needle, after its swing, will not return entirely to zero but generallywill stabilize at some value above zero, depending upon how completely the film of the capacitor is formed and on its leakage resistance. The amount.of leakage resistance in ohms can be read on the ohms scale in the usual manner, i.e., as 100 or 1000 times the actual reading on the meter, depending upon the meter scale used. In using the M9B Meter to measure the leakage of capac- itors, a lov1 voltage (4.5 volts) is applied, as compared to the usual operating voltages, Therefore, this test, in general, imposes a less severe condition than the service voltages to which the capacitor is normally connected. Leakage resistance at the low voltage at which the test is made should generally be 100,000 ohms or greater, for capacitors in good condi- tion. The amount of leakage which can be tol- erated depends upon the circuit usage of the capacitor, Leakal!,e current, of course, is con- verted into heat loss in the capacitor, and when appreciable, may hasten the deterioration and failure of the capacitor. 4. MAINTENANCE (A) Voltage Accuracy 4,01 No regular routine accuracy tests are required but it is recomi~ended that the d-c voltmeter be occasionally checked against a voltmeter of known accuracy. The permissible error is 2 per cent. of full scale, at any point on a scale. 4.02 The a-c checked curacy. The of full scale voltmeter may be occasionally against a voltmeter of known ac- permissible error is 5 per cent. at any point on the scale. (B) Battery Replacement 4.03 The battery should be replaced when it is impossible to adjust the meter pointer to the zero ohms mark when the test leads con- nected to the X and RxlOO jacks are short-cir- cuited (Paragraph 3.09), or when frequent ad- justment of the BATTERY ADJUSTMENT knob is re- quired when measuring resistance. If desired, the voltage of the battery may be measured without removing it from the meter as follows: ( 1) Arrange the meter for d-c voltage meas- urement.

(2) Connect one jack and the 15V pin jack. test lead to the X pin other test lead to the (3) Short-circuit the test leads and read the battery voltage on the 0-15 volt scale. 4.04 When replacement of the battery i s re- quired, use one of the followin g 4-1 / 2 volt batteries which have suitable chara cte r- istics and the proper type terminals for use in the meter. Bright Star 03-17s Eveready -781 Burgess 536o Ray-0-Vac 531R Bond 317 4.05 The lo\•1er portion of the meter casing is removable from the meter top panel by loosening the four scre ws which are located on the face of the panel near the edges, The bat- tery slides into a bracket formed to fit the battery and mounted on the rear of the meter housing. The leads to the battery are equi pped with spade terminals to fit under the screw terminals of the battery. The RED lead connects to the positive(+) terminal oTThe battery, 4.06 A coating of nonfluid oil (New York and New Jersey Lubricant Co, No. K-000) is applied to the edges of the casing and panel which fit together, in orde~ to pr~vide a mois- ture seal, Care should be taken not to wipe off this oil v:hen the case is opened, so that the seal can be maintained when the casing is put back together. A rubber gasket may be pro- vided on some meters in place of the oil or may be obtained if preferred. (Part 6.) ISS 1, SECTION 100-513-101 4,07 The screws holding the casing and pane together are 6-32 (,138-32), 5/8 11 long, oval-head machine screws, 5. REPAIR (A) General 5,01 The re placement of parts in the field, ot her t han replacement of the battery, is not recommended, since the calibration of the meter may be affected by variations in re- placement parts. If, however, parts are re- moved or replaced for any reason, the follow- in g instructions should be carefully followed, 5.02 All apparatus parts are attached to the underside of the top panel of the meter (Fie. 10), This panel maybe removed by taking out the four screws which attach it to the me- ter case, The edges of the panel and case may be coated with oil, or a rubber gasket may be provided in order to moisture-seal the meter. If a coating of oil is used, take care not to wipe it off when removing the top panel or mak- ing repairs, The oil used for this purpose and the rub ber gasket are listed in Part 6. 5.03 Identification of Leads. If it is neces- sary to re move parts from the meter for replacement or to remove leads or parts in or- der to gain acces11 to a defective part, make a record of the connections removed and of the location of any part removed, in ord ·er that the connections and parts can be correctly replaced. 5,04 Electrical Connections. When replacing internal wiring, clip the leads as close as possible for satisfactory connection. Take care to use only enough solder to make a secure BATTERY 8 1 RESISTOR P l RESISTORS R 7 THROUGH Rl6 ANO R2.0 -- --..-- PIN JACK CONNECTORS SWITCH 01 SWITCH 03 Fig, 10 - Location of Parts of M9B Meter ESISTOR BRACKET Page 9

SECTION 100-513-101 connection. Do not heat the tenninal or con- nection more than necessary to avoid possible damage to resistors, rectifier, etc. Caution: Never change the location of parts or wiring leads. Such a change may necessitate complete recalibration of the meter, Never chan e the len th o wiring eads. Use o. gauge wire. Moisture-resistant wire,Western Elec- tric Company D-142203, No, 22 gauge, solid or stranded, or KS-9819 wire is used in wiring the meter; this or its equivalent should be used for re- pairs, CLAMPING RING ' "7 r ~~ cf BATTERY V HOLDER Fig, 11 - Location of Parts of M9B Meter - Battery Holder and Meter Unit Re- moved 5 .05 Replacement of Parts, In replacing parts, take care to replace all parts in the same manner as originally installed. Be par- ticularly careful to replace the phenol-fibre insulating washers and bushings correctly. (B) Meter Unit 5,06 The meter unit is housed within a cylin- drical phenol-plastic wall which is.part of the top panel (Fig. 11). If it is necessary to remove the meter unit, it must be handled with care, and particular care must be taken when replacini;; the unit in its housing as cov- ered by Item ~6) below. Instructions for re- moving and replacing the meter unit follow: (1) Disconnect the leads from the battery and slide the battery from its holder. Page 10 (2) Remove the battery holder by removing the screws which attach it to the meter unit housing, (3) Loosen the two screws which fasten the spring clips and turn the clips clear of the meter unit. (4) Note t~e color of the lead attached to each of the meter tenninals on the rear of the meter unit, Disconnect these leads by removing the tenninal screws. (5) Place the palmof the hand over the me- ter unit and turn the panel face upward so that the meter unit slides out into the hand. (6) Before replacing the meter unit in the housing, carefully note the position of the turned-up brass tab close to the center of the meter assembly which deter- mines the zero setting of the pointer (Fig, 11). This brass tab must be engaged by one of the small slots in the zero corrector which is 'mounted in the center of the glass meter window. Holding the meter unit face upward in the palm of the hand, carefully slide the meter panel housing down over it in such a way that the relative position of the brass tab and the engaging slot of the zero corrector will be approximately right; then v•:hen almost fully in place, carefully turn the meter unit in the housing until the pointer adjusting tab slides in- to the slot in the zero corrector. If the meter unit face is not lined up straight in the shell, carefully rotate the meter unit in order to position the dial properly• keeping the brass tab and zero corrector engaged. Use care in perfonning this oper- ation since serious damage may be done to the meter unit by careless or rough han- dling, (7) Holding the meter unit in place, turn the panel fa_ce down; reposition the spring clips; replace the meter unit ter- minal leads, the battery holder, and the battery. (8) Replace the panel on the casing, place on a level surface, and adjust the zero reading of the pointers by turning the zero corrector with a screwdriver or small coin. (C) Meter Glass and Zero Corrector 5,07 The meter glass is moisture-sealed to the meter case by caulking between the outer rim of the glass and the case. A light- colored plexiglass ring, within the cylindrical meter unit housing, is held against the window

by a forced-in brass clamping ring. If it is necessary to replace the glass window and zero corrector assembly, proceed as follows: (1) Remove the meter unit as covered by Paragraph 5.o6 above. (2) Using a thin-bladed screwdriver, pry the brass clamping ring away from the inside of the meter unit housing at one point, bending the brass away sufficiently so that long-nose pliers can be inserted to grip it. (3) Grasp the bent part of the brass ring with the pliers and remove the ring, (4) Turn panel face upward so that the plexiglass ring will slide out. (5) From the top of the panel, pry the glass away from the case by inserting a small screwdriver blade or knife blade. Carefully scrape the old caulk from the case. (6) Reassembling, seal the glass to the meter case with Hallemi te No. 770 caulk mixed with 3 per cent, litharge. If Halle- mite caulk is not available, use G,E.Co, Glyptal mixed with enough talc to give it body, Wipe off any excess before it sets. 155 1, SECTION 100-513-101 (7) The clamping ring may sometimes be used again if carefully reshaped with pliers, or a new ring maybe used. Push the clamp- ing ring down evenly until it rests firmly against the plexiglass ring, A wooden block, if available• may be used to force the clamping ring in. (8) Replace the meter unit and adjust the zero reading as covered in Paragraph 5.o6, Item (5) through (7) above. (D) Pin Jacks 5.08 The pin jack assemblies are screwed into drillings in the underside of the top panel, Each pin jack (Fig, 12) consists prin- cipally of the outer shell which screws into the panel, the pin jack body, a lock nut, and lock washer. Two lengths of pin jacks are used. Additional washers and nuts are added to the stem of the longer jacks for connecting wires, lugs, etc., as required. A pin jack, if taken • ASSEMBLED PIN JACK .. OUTER SHELL Fig. 12 - Pin Jack Assembly and Parts Notes, l, Wires designated "A" shall be per Spec, KS-9819 ,{/e2 AWG Solid Conductor, 2, Wires designated "B" shall be per Spoo, KS-9819 ,(/e.2 AWG Stranded Conductor, :,. Wires designated "c" shall be furnished with appara.tua, 4, Wires designated "T" shall be ,(/1.22 AWG Bare Tinned Copper, 5. Wires designated "S" shall be covered with No, 17 Varnish Tubing per LRM 186. 6, All soldering shall be in accordance with Spec. KS-512 Method E, using Solder fl}, Flux No. 2, 7. All connections to be mechanically secure before soldering. 8. Battery leads shall be arranged so that cord tips do not Come into contact with any electrical connections. 9. No. 11 Varnished Tubing per LRl1 186. approx. 1/2 in. long shall be assembled over the ends of these leads and soldered connections, Fig. 13 - M9B Meter - Wiring Diagram Page 11

SECTION 100-513-101 apart for repair or inspection, must be care- fully reassembled as follows~ (1) Screw the pin jack into the shell as far as it. will 1,0; then back it off a little (not over 1/4 turn). (2) Place the lock washer and lock nut on the protruding end of the pin jack and screw the lock nut down to hold the pin jack in place, Use care that the inner part is not turned from the position de- scribed in Item (1) above whenthelock nut is tightened. If the tips of the inner jack "bottom," they will not grip properly when the pin terminal of the test load is inserted, (3) If pin jacks do not grip tightly, the slotted ends of the tips of the pin .jack body may be adjusted using pliers at the time that the pin jack is disassembled. (4) It is unnecessary to remove the outer shell from the panel in order to in- spect the body of the jack, Do not remove the jacks from the panel unnecessarily, as the bushing threads may be da.r.1aged by doing this repeatedly or carelessly. 6. REPLACEMENT PARTS 6.01 The following is a list of the more readi- ly replaceable parts of the M9B Meter: Part Battery, 4-1/2 volts. Page 12 12 Pages nanufacturer and No. Bright Star 03-17S, Eveready 781, Burgess 5360, Bond 317 or Ray-0-Vac 531R Part Gasket, rubber; for use between top panel and case. Meter Unit Assembly (meter movement, scale plates and pointers), Oil, nonfluid; for moisture-sealing top panel to case. Pin Jack (longer size) Potentiometer (battery adjustment) Resistor; for replacing R-4; may require sli ght modification of resis- tance of secondary wind- ing to obtain accurate readin gs on 0-1000-ohm scale. Zero Corrector Assembly (zero cor- rector moimted in hardened glass me- • ter window) Manufacturer and No. W. E. Co. BA-109230 H. E, Co, P-480532 N, Y. and N. J, Lubricant Co. :/IK-000 \;. E, Co, P-480657 Allen-Bradley J-Ul032-P4048-4 W, E, Co, D-166804, with secondary wind- ing of 33.5 ohms W, E. Co. P-285979