Orban 418A Manuals

OPERATION AND MAINTENANCE MANUAL STEREO LIMITER MODEL 418 orbcin 1525 Alvarado Street, San Leandro, CA 94577 USA Phone: (1) 510/351-3500; Fax: (I) 510/351-0500; E-Mail: [email protected]; Site: www orban com P/N: 95012.000.04 STEREO LIMITER MODEL 418A TABLE OF CONTENTS Page Replacement o'f Components in REGISTRATION INTRODUCTION 1 Printed Circuit Boards Comments on 1C Opamps CIRCUIT DESCRIPTION General INSTALLATION: MECHANICAL 1 Input Buffer and Broadband AGC Program Controlled Pre-emphasis INSTALLATION: ELECTRICAL 1 De-emphasis and Output Stage Power Supply Input 1 Output 1 FACTORY SERVICE Power 2 OPERATING CONSIDERATIONS 2 SHIPPING INSTRUCTIONS OPERATING INSTRUCTIONS 3 APPENDIX A: ALIGNMENT INSTRUCTIONS Required Instrumentation MAINTENANCE 3 Setup for Complete Alignment Alignment Procedure Preventive Maintenance 3 Corrective Maintenance 4 APPENDIX B: SPECIFICATIONS >o if> to 'O *o n rv |\ co co OD co REGISTRATION CARD The original purchaser should have received a postpaid Registration Card packed with this manual. Registration is of benefit to you because it enables us to tell you of new applications, possible performance improvements, service aids, etc., which may be developed over the life of the product. It also provides us with the date of sale so that we may more promptly respond to possible claims under Warranty in the future (without having to request a copy of your Bill of Sale or other proof of purchase). Please fill in the Registration Card and return it to us. If the Registration Card has become lost or you have purchased the unit used, please photocopy the image of the card reproduced below and send it to us in an envelope. Use the address shown on the title page. Model # Serial # Name or Title _____ Organization — Street City/State/Country Zip or Mail Code Purchased from__ City Date of Purchase Nature of your application How did you hear about it? Comments: Fig. I: REGISTRATION CARD WARRANTY The Warranty, which applies only to the first end-user of record, is stated on the Warranty Certificate on a separate sheet packed with this manual. Save it for future reference. INTRODUCTION The principal use of your new 418 Limiter is to condi- tion arbitrary complexaudio signals (not just single tracks, although the 418 may be used with these, too) in such a way that they can be recorded on tape or opti- cal film without overload, excessive noise, or distortion due to excessive high frequencies. In order to do this while introducing minimal artifacts into the signal, the 418 incorporates a highly refined program-controlled re- lease time circuit, as well as a separate high-frequency limiter which can control the high frequencies present in the program on an instantaneous basis without distortion and without disturbing the basic program loudness. The release time and high-frequency limiter are both adjustable by the user in order to obtain the desired amount of high-frequency control, level control, com- pression, and density augmentation . The controls have been arranged to minimize the probability of audible side-effects of an undesirable nature regardless of their settings Some uses of the 418 include: (1) mixing through while doing multitrack reductions in order to save time while doing radio commercials, demo sessions, and the like; (2) conditioning recorded program material so that it can be copied onto cassette or low-speed tape without excessive hiss and/or high-frequency distortion; (3) trans- fering from magnetic to optical film; (4) transferring from disc to 7.5 ips tape cartridge in broadcast stations; (5) re- cording production work through in broadcast production studios; and (6) transferring from tape to disc (with certain limitations — see OPERATING INSTRUCTIONS). Other applications will doubtless suggest themselves to the creative engineer The 418 is not rigorously RFI/EMI shielded, and its output contains substantial amounts of fast overshoots. It is therefore specifically not recommended for driving broadcast transmitters. Orban Associates Division manu- factures a line of devices, the OPTIMOD-FM and the OPTIMOD-AM, specifically designed for this purpose. INSTALLATION: MECHANICAL The 418 Limiter is designed to mount in a standard 19" (48.26 cm) rack, and requires 3.5" (8.89 cm) of vertical space. All operating controls are accessible from the front. The fuse, AC line cord, and audio connections are made from the rear. The audio connects to a Jones 140-type barrier strip (^5 screw), and connections can be made by means of spade lugs or a fanning strip, in those cases where quick connects/disconnects are required. In a rack mount installation, the 418 will pick up its chassis ground from the rack. Be sure to measure the re- sistance from chassis to rack after installation and correct any high-resistance situations before proceeding. It may be necessary to scrape the paint from the rack and/or the rear of the panel in order to effect an adequate ground. It is advisable to make sure that the rack is grounded to some earth ground simultaneously. Grounding of racks and other equipment to power line conduit grounds as a sole means of grounding often creates troublesome prob- lems. In rack -mounting the 418, very strong AC magnetic fields should be avoided because these can introduce hum into the input transformers. In addition, the 418 should not be mounted directly over equipment producing large amounts of heat, like vacuumtube power amplifiers. Ambient temperature should not exceed 45°C (11 3°F ) when the 418 is powered. If the 418 is rack-mounted, the jumper on the rear barrier strip connecting terminal 7 (signal ground) to terminal 8 (chassis ground) should be removed to avoid ground loops. If the 418 is used in a portable situ- ation, this jumper should be retained in order to assure that the chassis is grounded. When the jumper is retained, it is advisable to terminate the line cord with a three- prong to two-prong AC adapter in order to avoid intro- ducing ground loops through the AC power line grounding system. The center (ground) prong on the 418 line cord (green wire) is connected directly to the chassis. INSTALLATION: ELECTRICAL Input; The input of the 41 8A is a 100K ohm balanced bridging input. It is synthesized by means of an electronic differ- ential amplifier; no transformer is used. Absolute input clipping occurs at +21 dBm; higher levels require use of an external balanced pad. With the INPUT ATTEN full clock- wise, -10 dBm will produce 10 dB gain reduction. It is important that both (+) and (-) inputs be driven by a source impedance of 600 ohms or less in order to assure best "common mode rejection" (i.e., ground loop hum rejection). If the device driving the 41 8A has a balanced output, the two output leads should be driven directly into the (+) and (-) inputs of the 41 8A. If the device driving the 41 8A has an unbalanced output, it snould also be connected to the 41 8A with a two conductor shielded cable. The black wire should be connected bet- ween the driving device's signal ground and the 418A's (-) input. The second wire should be connected between the driving device's output and the 418A's (+) input. This arrangement takes maximum advantage of the hum- reducing ability of the 418 A's balanced input. In either case, the shield of the interconnecting cable should be connected to chassis ground at one end only. No special RF suppression techniques have been used in the 418A. If RF interference is experienced in high RF fields, we suggest bypassing audio inputs, outputs, and the power line to chassis ground through 0.001 mfd ceramic capacitors with short as possible leads. Be sure that the voltage rating of the power line bypass capacitor is at least 1 .6 kV, and that bypassing occurs after the fuse to avoid a potential fire should the capacitor short . Because the chassis metalwork has not been designed to be rigorously RF-tight, it is unlikely that the 418A could be operated immediately adjacent to a transmitter. In a broadcast production studio, sufficient RF suppression usually exists so that successful operation can be easily obtained. Output: The output of the 418 is unbalanced, and follows the OUTPUT ATTEN control, which is configured as a standard potentiometer. Maximum output resistance occurs with this control at 12 o'clock; in this case, the output resis- tance is approximately 400 ohms. Maximum available level is +1 3 .4 dBm