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Model 1200 Powermixer SERVICE MANUAL
ISSUE NO. 1

Manufactured by

SHURE BROTHERS INC. 222 Hartrey Avenue Evanston, Illinois 60202-3696

Copyright 1988, Shure Brothers Inc. AL954 (HE) 27A8187

Printed in U.S.A.

SPECIFICATIONS
Output Clipping Level MINIMUM CLIPPING LEVEL OUTPUT +29 dBV (28 V) SPEAKER +18 dBV (7.9 V) MONITOR +18 dBV (7.9 V) PROGRAM MIX +16 dBV (6.3 V) PHONES +18 dBV (7.9 V) TAPE Impedance FOR USE WITH ACTUAL INPUTS 75 to 600 1 k LO Z MIC 100 k or less 130 k HI Z MIC 10 k or less 50 k AUX 10 k or less 50 k PA OUTPUTS 2.4 k 2 k or more MONITOR 2.4 k 2 k or more PROGRAM MIX 2 k or more 2.4 k TAPE 430 4 or more PHONES 4 or more SPEAKER Hum and Noise Less than -126 dBV equivalent input hum and noise (20 Hz to 20 kHz, LO Z input to SPEAKER output) Noise Less than -127 dBV equivalent input noise (300 Hz to 20 kHz, LO Z input to SPEAKER output) Signal-to-Noise Ratio Greater than 80 dB (below full output) at typical control settings Phantom Power 24 Vdc ± 10% open circuit, 1.8 k series resistance Power Requirements 120 Vac ± 10%, 50/60 Hz, 420 watts typical with no ac receptacle load AC Convenience Receptacle 120 Vac, 100 watts maximum Certifications Listed by Underwriters Laboratories Inc. and by Canadian Standards Association as certified Environmental Conditions Operating Temperature: -7 to 43°C (20 to 110°F) Storage Temperature: -40 to 74°C (-40 to 165°F) Relative Humidity (Operating and Storage): 0 to 95% Overall Dimensions 191 mm H x 483 mm W x 343 mm D (7-½ x 19 x 13-½ in.) Weight 12.3 kg (27 lb) 18.2 kg (40 lb) in A1200C Carrying Case RECOMMENDED LOUDSPEAKERS AUDIOMASTER Model 3200, 100 W, 8 , vented two-way speakers OPTIONAL ACCESSORIES Carrying Case. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1200C Input Expansion Module* (2 channels, 2 each HI Z and LO Z inputs). . A1200MX Speaker Cable, 15 m (50 ft) with phone plugs . . . . . . A50SC Line Matching Transformer (LO Z to HI Z) . . . . . . . . . A95UF 240-V Conversion Kit* . . . . . . . . . . . . . . . . . . . . . . . . RKC209 Phono Preamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M64A *For installation by qualified service personnel only.

Type Mono Powermixer Frequency Response Flat +1, -3 dB, 40 Hz to 20 kHz (any input to any output) Inputs Six input channels: six unbalanced high- and/or balanced low-impedance inputs; channels 1 and 2 highimpedance inputs switchable to Aux level; available expansion modules* each contain 2 high- and 2 lowimpedance microphone inputs; two modules (4 channels) can be added to each 1200 Power Output (1 kHz, 120 Vac, 1% THD) 200 watts minimum with 4 ohm speaker 120 watts minimum with 8 ohm speaker Distortion THD typically less than 0.15% at 1 kHz, 0.35% at 70 Hz and 20 kHz (180 watts to 4 ohms, measured from lowimpedance input, Input Attenuation, individual channel and Master Volume controls at typical user settings) IM distortion typically less than 0.4% (116 watts to 4 ohms, Input Attenuation, individual channel and Master Volume controls at typical user settings) Low- and High-Frequency Equalization (Individual channel and Monitor) ±10 dB at 100 Hz and 10 kHz Input OVERLOAD Indicators Illuminate 3 dB before clipping of input preamplifier or equalizer stage Power Amp Limiter Threshold: 1.5 dB below speaker output clipping level Input signal range: 15 dB beyond limiting threshold Output PEAK/LIMIT Indicator With Limiter Out: Lights 2 dB before clipping at speaker outputs With Limiter In: Lights 0.5 dB before onset of Limiter action Output NORMAL Indicator Lights when speaker output level is greater than 1.4 Vrms (0.5 W into 4 ohms) Input Sensitivity (full power output) BAL LO Z: -66 dBV (0.5 mV) HI Z: -44 dBV (6.3 mV) AUX: -26 dBV (50 mV) PA INPUT: 0 dBV (1.0 V) Input Clipping Level
INPUT CLIPPING LEVEL ATTENUATION

-33 to -3 dBV (22 to 707 mV) HI Z -11 to +18 dBV (281 mV to 8.41 V) AUX +6 to +36 dBV 2 to 63 V PA INPUT -1 dBV (891 mV) Voltage Gain (at 1 kHz)
INPUT OUTPUT

BAL LO Z

0 to -30 0 to -30 0 to -30 -

SPEAKER PGM MIX MONITOR PHONES

TAPE

LO Z HI Z AUX PA

95 73 55 29

dB dB dB dB

65 dB 43 dB 25 dB -

71 dB 49 dB 31 dB -

82 60 42 16

dB 51 dB dB 29 dB dB 11 dB dB -

MODEL 1200 SERVICE MANUAL TABLE OF CONTENTS
Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . For Years of Dependable Service . . . . . . . . . . . . . . . . . . . . Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . Service Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General Service Procedure . . . . . . . . . . . . . . . . . . . . . . . AC Voltage Measurements . . . . . . . . . . . . . . . . . . . . . . . . DC Voltage Measurements . . . . . . . . . . . . . . . . . . . . . . . . Resistance Measurements . . . . . . . . . . . . . . . . . . . . . . . . Chassis-Mounted Boards and Components . . . . . . . . . . A1 Reverb Pan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SHR-11 (and SHR12) Power Amplifier Board Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SHR-11 Potentiometer Adjust . . . . . . . . . . . . . . . . . . VR1101 Output Voltage Offset . . . . . . . . . . . . . . . . VR1102 Driver Balance . . . . . . . . . . . . . . . . . . . . . VR1103 Idle Current . . . . . . . . . . . . . . . . . . . . . . . SHR-12 Temperature Sensor Board . . . . . . . . . . . . . . . VR1201 Temperature Sensor Threshold . . . . . . . . . . SHR-14 Main Board . . . . . . . . . . . . . . . . . . . . . . . . . . . VR1401 Power Amplifier Limiter Threshold . . . . . . . . Rear-Panel Boards and Components . . . . . . . . . . . . . . . SHR-10 Input-Output Board . . . . . . . . . . . . . . . . . . . . . SHR-03 Aux/Mic Board . . . . . . . . . . . . . . . . . . . . . . . . SHR-02 Hi-Z Input Board . . . . . . . . . . . . . . . . . . . . . . . SHR-01 Lo-Z Input Board. . . . . . . . . . . . . . . . . . . . . . . SHR-13 Speaker Output Board . . . . . . . . . . . . . . . . . . B1 Fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S3 Phantom Power Switch . . . . . . . . . . . . . . . . . . . . . . Front-Panel Boards and Components . . . . . . . . . . . . . . . SHR-04 Channel Board (6). . . . . . . . . . . . . . . . . . . . . . Front Mounting Panel . . . . . . . . . . . . . . . . . . . . . . . . . . SHR-05 Master Control Board . . . . . . . . . . . . . . . . . . . SHR-09 Limiter Board . . . . . . . . . . . . . . . . . . . . . . . . . SHR-06 Headphones Output Board and SHR-07 Headphones Control Board . . . . . . . . . . . . . SHR-08 Indicators Board . . . . . . . . . . . . . . . . . . . . . . . S2 On/Off Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1200MX Input Expansion Module . . . . . . . . . . . . . . . . . Checking Active Components . . . . . . . . . . . . . . . . . . . . . Ferrite Beads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Service Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optional Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 2 3 3 3 3 3 4 5 5 5 5 5 5 5 6 6 6 6 6 6 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 8 9 9 9 9 9

DESCRIPTION
The Shure Model 1200 AUDIOMASTER Powermixer is a compact, flexible microphone mixer with six inputs for high- or low-impedance sources and a 200-watt power amplifier. The 1200 is human-engineered for ease of setup and operation. Connection of microphones, speakers and other equipment (tape recorder, equalizer, effects device, remote amp, etc.) is fast and convenient. The 1200 is rack-mountable or portable. Its 6 inputs are expandable to 8 or 10 inputs through the use of A1200MX Expansion Kits. Inputs accept both high- and low-impedance microphones (dynamic, ribbon or condenser), as well as amplified instruments or other high-level sources. Individual channel input attenuators with overload indicators permit precise gain control to prevent input overload. The 1200 has built-in reverberation with individual channel and overall level adjustments.
®

Other effects devices or an equalizer can be connected through a post-master control program loop. An integral power amp limiter prevents overload distortion over a wide signal input range. Pre-volume monitor send controls and pre-master volume tape output provide maximum versatility in stage or recording applications. The control panel has color-coded knobs for ease of adjustments, while LED indicators give instant notice of operating status. In addition to the A1200MX Expansion Module, the following accessories are available for the 1200: A1200C Carrying Case, A95UF Line Matching Transformer, RKC209 240 V Conversion Kit, and M64A Phono Preamplifier. The 1200 is Listed by Underwriters Laboratories, Inc., and listed by Canadian Standards Association as certified.

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FOR YEARS OF DEPENDABLE OPERATION...
The AUDIOMASTER® System is exceptionally well designed, with all components of the highest quality, operating well within their respective ratings to assure long life. The following list of Do's and Don'ts describes minimal operating precautions and maintenance to provide years of dependable service. DO use a 16 AWG or larger, heavy-duty, 3-conductor extension cord when additional line cord length is needed. DON'T replace the rear-panel fuse with a different size or type. Use only 5 A, 250 V, Type 3AG. DON'T operate the Powermixer with its air vents blocked; don't place it on a radiator or heat-producing equipment. Avoid operation in direct, hot sunlight. DO unplug the Powermixer before cleaning. Use only mild detergent and a damp (never wet) cloth to clean the outer surfaces; Don't use strong solvents or cleaning fluids. DON't use unbalanced low-impedance microphones with the PHANTOM 24V switch on; turn off the switch if not required for powering condenser microphones. If phantom power is in use, connect unbalanced low-impedance microphones through a line matching transformer (Shure A95UF) to a HI Z input. Phantom power will not affect balanced low-impedance dynamic microphones. DON'T risk fire or shock hazard by operating the Model 1200 in the rain. TROUBLESHOOTlNG Should any difficulty be encountered in operation of your AUDIOMASTER System, the trouble can often be traced to some simple source. The following is offered as a basic guide to solving this kind of problem.

SYMPTOM Powermixer is "dead" (no output, POWER LED off)

PROBABLE CAUSE AND CORRECTION 1. Check that ac power source is "live" and Model 1200 is plugged in. 2. Check that POWER switch is on. 3. Check that rear panel fuse (5 A, 250 V) is good. 4. If the 1200 has turned off due to excessive internal temperatures, allow at least an hour for cooling, and reactivate unit. If difficulty persists, refer to General Service Procedure in this manual. 1. Check total speaker load (must be no lower than 4 ohms) and for possible shorted speaker cable. 1. Check air vents for blockage. 2. Check that internal fan is operating (fan located on rear panel). 3. Turn MASTER volume control down for several minutes to allow proper cooling. If difficulty persists, refer to General Service Procedure. 1. Check for defective or improperly connected speaker cables. 1. Check settings of channel VOLUME and MASTER VOLUME controls. 2. Check connections to EXTERNAL DEVICE LOOP 1. Replace with identical fuse (5 A, 250 V, 3AG). 2. If second fuse blows, refer to General Service Procedure. 1. Make sure similar microphones are used on both inputs, and microphone impedances match the inputs used. 2. Make sure a low-impedance microphone is not used with aux level equipment on other input. 3. Make sure MIC/AUX switch is in MIC position (Ch. 1 and 2 only). 4. Make sure microphone switches are on; check microphone cables.

OVERLOAD LED illuminates, either A. Flickering with program material, indicating abnormal speaker load B. Continuously to indicate power amplifier shutdown

No signal at speaker (all other functions appear normal), either A. NORMAL LED illuminated, or B. NORMAL LED not illuminated

Fuse blown One of two inputs on same channel not working properly (both 1/4-inch and 3-pin jacks in use)

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SYMPTOM INPUT OVERLOAD LED flashing NOTE: Occasional flashing is acceptable Loud clicks when certain microphones or cables are used

No MONITOR output (program output normal)

Sound quality poor (weak or thin)

PROBABLE CAUSE AND CORRECTION 1. Adjust INPUT ATTENUATION counterclockwise to reduce channel input level. 2. Reduce input signal level at source. 1. Make sure PHANTOM 24V switch is not on (when not needed). 2. Make sure unbalanced low-impedance microphone or cable is not used when PHANTOM switch is on. 3. Check for defective microphone cables. 1. Make sure channel MONITOR and MONITOR MASTER controls are turned up. 2. Make sure controls on external equipment connected to Monitor output jack are turned up. 3. Check for defective cable from MONITOR output jack. 1. Check for excessive treble boost or bass cut on equalization controls. 2. Check PROGRAM and MONITOR output jacks for signal quality (if acceptable, problem is in power amplifier section). 3. Check for defective cables. 4. Check impedance match (high- or low-impedance mics) at input.

SERVICE INSTRUCTIONS
EXTERNAL PARTS The knobs and feet can be replaced without disassembling the 1200. All knobs are of the pull-off type, and are color-coded by function. The Equalization knobs are dual concentric types; all other knobs are single. DIAGNOSIS A simple method of localizing problems without opening the 1200 is as follows. Turn off the Power switch. Do not connect a speaker or headphone load. Set all controls of the channel under test only to full clockwise (other channel volume and monitor controls full counterclockwise), except: Reverb Return full counterclockwise, and Eq controls centered. Turn the unit on and apply a 0.5 mV, 1 kHz test signal across pins 2 and 3 of one of the Bal Lo Z input connectors. Normal voltmeter readings taken at each output connector are given in Table 1. Similarly, a 5 mV signal inserted in a HI Z input, 50 mV in an AUX input, or 891 mV in the Power Amp and Monitor Inputs will yield similar output voltages. This method is useful for saving time in localizing problem areas. Internal servicing should be performed only by qualified service personnel. TABLE 1. NOMINAL TEST VOLTAGES OUTPUTS INPUT Input Spkr Prgm Mix Mon Phones Tape LO z 0.5 mV 28 V 890 mV 1.78 V 6.31 V 178 mV HI Z 5 mV 22 V 708 mV 1.41 V 5.01 V 141 mV AUX 50 mV 28 V 890 mV 1.78 V 6.31 V 178 mV PA 891 mV 25 V ----5.62 V --WARNING Voltages in this equipment are hazardous to life. Refer servicing to qualified service personnel. EXTERNAL FUSE REPLACEMENT To replace line fuse F1 (with no apparent problems in the Powermixer), disconnect the line cord from the ac source and remove the rear panel fuseholder cap by pushing it in and turning it counterclockwise (either a screwdriver or fingertip may be used.) Replace the defective fuse only with a 5A 250V Normal Blow type.

CAUTION If trouble symptoms (overheating, erratic operation, etc.) were apparent before the fuse blew, or if the replacement fuse blows, a qualified service person should troubleshoot the Powermixer carefully to find the source of the problem. Do not continue to replace fuses; have the trouble corrected. SERVICE ACCESS Disconnect the 1200 from its power source. To open the unit for servicing, remove ten screws and lockwashers from the top and five from each side of the cover. The cover can then be lifted off exposing the internal parts (see Figure 1).

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PRINTED CIRCUIT BOARD AND PARTS LOCATION FIGURE 1 WARNING After replacing high-voltage parts such as the fan, power cord, rear panel convenience receptacle, or printed wiring assemblies SHR-11, SHR-12, or SHR-14 (or their components), make certain that a dielectric voltage breakdown test is performed before connecting the unit to a power supply. With the unit disconnected from the ac source, turn the unit on and measure the resistance between the ground contact of the power plug and each of the other two prongs. This resistance should measure infinite. Then measure the resistance between the plug ground and exposed metal parts of the chassis, screws, connectors, fan grille, etc. This resistance should be zero ohms. If any measurements are recorded outside the specified limits, a shock hazard exists. The unit must be repaired and rechecked before it is returned to operation. IMPORTANT: When removing any printed wiring board, be sure the wires and connectors detached from the board are identified for proper reconnection. This may be done by affixing a piece of masking tape marked with the reference designation (connectors) or terminal letter or color (wires). NOTE: Any cable ties that were loosened or removed must be tightened or replaced after servicing. CAUTION Similar wire colors and connectors with the same number of pins are used in different circuits; make sure proper reconnections are made. Push-on connectors must be removed by pulling straight out. The side of a small screwdriver blade inserted between the free and fixed connector can sometimes be helpful in separating the connector. Do not apply side force when removing or reconnecting terminals, or damage may result. Reference to the service illustrations will be helpful in case of difficulty.

GENERAL SERVICE PROCEDURE To isolate a problem area, a general procedure is as follows. If the Powermixer is completely dead, check the ac power source, line cord, and fuses (external and internal). If the unit turns on but operation is abnormal, check the chassis power supply output (-56 Vdc between test point SHR-11-AB and ground, and +56 Vdc between test point SHR-11-AA and ground; -15 Vdc across C1421, +15 Vdc across C1420, and +24 Vdc between P1404-A and ground). If the measured dc voltages are correct, perform additional AC and DC Voltage Measurements as described below to isolate the problem.

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AC VOLTAGE MEASUREMENTS Numbers within rectangular symbols on the circuit diagrams denote ac voltages at that point under the following test conditions: 1. Voltages measured with respect to chassis unless otherwise indicated. 2. Line voltage: 120 V, 60 Hz. 3. Test signal of 0.5 mV across pins 2 and 3 of connector J101. 4. AC voltage measurements may vary ±20% from values shown. 5. Measurements made with ac voltmeter of 1 megohm or greater input impedance. 6. No load on Speaker Outputs. 7. All controls (of channel under test only) full clockwise except Equalization controls centered. 8. Reverb Return full counterclockwise. 9. Limiter switch and Phantom switch in Off position. 10. Monitor Master control clockwise. DC VOLTAGE MEASUREMENTS Numbers within elliptical symbols on the circuit diagrams denote dc voltages at that point under the following test conditions: 1. Voltages measured with respect to chassis unless otherwise indicated. 2. Line voltage: 120 V, 60 Hz. 3. No input signal applied. 4. Dc voltage measurements may vary ±20% from values shown. 5. Measurements made with dc voltmeter of 11 megohms or greater input impedance. 6. Phantom switch in On position. RESISTANCE MEASUREMENTS With the ac line cord disconnected from the ac source and the Power On/Off switch off, the following ohmmeter measurements may be made. 1. Reverb pan output coil: approximately 360 ohms; input coils approximately 40 ohms. 2. Transformers may be checked for continuity of each winding. 3. To test transistors, ICs and diodes, refer to the section on CHECKING ACTIVE COMPONENTS. CHASSIS-MOUNTED BOARDS AND COMPONENTS The following printed wiring boards and components are chassis-mounted. SHR-11 POWER BOARD SHR-12 SENSOR BOARD SHR-14 MAIN BOARD A1 REVERB PAN POWER TRANSFORMER T1 REVERB PAN To remove the reverb pan assembly, turn the 1200 on its side (power transformer down) and remove the three screws holding the reverb shield to the chassis bottom. Turn the 1200 upright and remove the screw holding the reverb shield to the standoff attached to the parallel vertical interior shield. Disconnect the phono connectors at the bottom of the reverb pan assembly. Remove the four screws holding the reverb pan to the vertical metal interior shield, and lift the reverb shield and pan assembly out of the chassis holding the pan to the shield. (If necessary to free the reverb shield, remove the cable tie(s) holding the orange and white leads to the metal shield.)

To replace the reverb pan, connect the white lead connector to the reverb Input and the orange lead connector to the reverb Output. Use the previously removed screws to secure the reverb pan to the reverb shield, and to secure the shield to the chassis bottom and the parallel vertical interior shield. Be sure to replace any cable ties that were removed or loosened. SHR-11 AND SHR-12 POWER AMP BOARD ASSEMBLY The Power Amplifier Board Assembly consists of SHR-11 and SHR-12 mounted on the large aluminum heat sink. To separate the heat sink and its associated boards from the 1200, remove the screws holding the sink to the power transformer shield bracket, and those holding the sink to the metal shield that divides the fan from the input and output connectors and boards. Disconnect the connectors from P1101, P1102 and P1201, and unsolder the red, green, and white leads from AA, AB and AC, respectively, on SHR-11. (The opposite ends of leads AA and AB are connected to SHR-14, Main Board; the opposite end of lead AC is connected to SHR-13, Speaker Output Board.) The Power Amp Board is now free of the 1200. To replace parts on SHR-11, it is then necessary to remove SHR-11 from the large heat sink. Do this by removing the four Phillips screws holding the power transistors at the corners of the board, and the two Phillips screws holding the board on the brass standoffs. NOTES: 1. Removal of SHR-11 from the heat sink may damage the insulators below the power transistors. Therefore, when servicing SHR-11, be prepared to replace all four 802639FK insulators. If either predriver transistor Q1103 or Q1104 (mounted on the vertical heat sink fastened to SHR-11) is replaced, be prepared to replace insulator 802681FK beneath it. 2. If transistor Q1105, mounted on the solder side of board SHR-11, is replaced or if the board has been removed from the heat sink, make certain that Q1105 physically contacts the large heat sink after reassembly of the board to the heat sink is completed. Apply a small amount of Wakefield Type 120 Thermal Joint Compound to the top surface of the transistor in order to ensure proper heat transfer. To replace SHR-11 in the 1200, solder the red, green and white leads to AA, AB and AC. Connect the cable assembly with three leads from P1405, SHR-14, to P1101 ; and connect the cable with a single lead from P1407, SHR-14, to P1102. SHR-11 POTENTIOMETER ADJUSTMENT If any components are replaced on SHR-11, trimpots VR1101, VR1102 and VR1103 may require readjustment. Measure the SHR-11 voltages described in the following paragraphs. If measured voltages are not correct, make adjustments as follows. With power off, no input signal applied, and no load on the 1200's speaker output, turn VR1103 completely clockwise. Turn power on and allow unit to warm up or thermally stabilize for ten minutes prior to making the adjustments. See Figure 2 for trimpot locations.

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VR1101 OUTPUT VOLTAGE OFFSET ADJUSTMENT 1. Connect a dc voltmeter between SHR-11 terminal AC and ground (see Figure 2). 2. Adjust VR1101 so that V1 equals 0 V ±15 mV VR1102 DRIVER BALANCE ADJUSTMENT 1. Connect a dc voltmeter between CP1101 and ground (see Figure 2). 2. Adjust VR1102 so that V2 equals 1.2 V. VR1103 IDLE CURRENT ADJUSTMENT 1. After the unit has been turned on for at least five minutes, connect a dc voltmeter between R1126 and R1127 as shown (see Figure 2) and check the idle current. If the value of V3 does not equal 6.6 mV ±3.3 mV, use a razor blade to carefully remove from the top and side of VR1103 the old cement that prevented its adjustment from changing. 2. Adjust VR1103 so that V3 equals 6.6 mV ±3.3 mV. 3. Apply a drop of cement (white glue, hot melt glue, caulk, etc.) to VR1103 to eliminate movement due to vibration.

VR1201 TEMPERATURE SENSOR THRESHOLD ADJUSTMENT If U1201 or other SHR-12 parts are replaced, VR1201 will probably require recalibration as follows. 1. Turn off the unit long enough for the heat sink to reach ambient temperature. Remove all input signal sources and speaker loads. 2. Measure the heat sink temperature or ambient temperature around the heat sink. Consult the graph in Figure 3 to determine the proper voltage at test point CP1402. 3. Attach a dc voltmeter between CP1402 (+) and ground (-). 4. Apply power to the unit and quickly adjust potentiometer VR1201 on SHR-12 until the proper voltage is reached.

TEMPERATURE SHUTDOWN SENSOR CALIBRATION FIGURE 3 SHR-14 MAIN BOARD The 1200 contains four internal fuses mounted on the Main Board (SHR-14). If replacement becomes necessary, replace only with identical Normal Blow fuses: two 0.75 A 250 V, and two 8 A 250 V. Do not continue to replace fuses if a fuse continues to blow; have the trouble corrected. To remove SHR-14 from the chassis, remove the three Phillips screws on each of the long sides of the board and the single screw next to the two 8 A fuses on the short side of the board. This will allow the board to be lifted free of the chassis. If it is necessary to completely separate SHR-14 from the 1200, remove all seven connectors (be sure to label the four 4-pin connectors and their receptacles to ensure proper reattachment). Unsolder the six transformer and two fan leads from pins AA through AH, and the two ground leads connected to Al and AJ. Be sure to label leads also so they can be resoldered to the proper pins. Unsolder from connection pins AA and AB of SHR-11 the red and green wires attached to the solder side of SHR-14. (Remove cable ties as necessary.) The SHR-14 board can now be completely detached from the 1200.

SHR-11 POTENTIOMETER ADJUSTMENTS FIGURE 2 SHR-12 TEMPERATURE SENSOR BOARD To remove SHR-12 from the large heat sink, remove the Power Amplifier Board Assembly from the 1200 as described above. Then remove the two Phillips screws that hold SHR-12 to the small vertical heat sink. When replacing SHR-12, U1201 (mounted on the solder side of the board) must physically contact the vertical heat sink in order to ensure correct operation of the power amplifier over-temperature protection circuitry. In addition, apply a small amount of Wakefield Type 120 Thermal Joint Compound to the top surface of the IC to allow good heat transfer.

6

If any of the heat-sink-mounted parts (voltage regulators U1408, U1409 and U1410, or silicon rectifiers D1423 and D1424) is replaced, be sure to apply a small amount of Wakefield Type 120 Thermal Joint Compound between the component and the heat sink to allow maximum heat transfer. A number of components on SHR-14 are mounted on spacing insulators to keep them a measured distance from the board, e.g., R1460, D1422. If any of these parts is replaced, be sure to remount them the required distance above the board on spacing insulators as originally supplied. VR1401 POWER AMPLIFIER LIMITER THRESHOLD ADJUSTMENT This adjustment is made under the following conditions. 1. Terminate the Speaker Output in a 4-ohm resistive load. 2. Set the Master control and trimpot VR1401 on SHR-14 fully clockwise. 3. Set the Limiter switch to Out. 4. Connect the unit to a 120 Vac, 60 Hz power source and switch the unit on. 5. Drive one low-impedance input channel at 1 kHz with its channel control fully clockwise. (Turn all the other input channel Volume Controls fully counterclockwise.) Increase the input signal until the signal at the Speaker Output just visibly clips. 6. Reduce the input signal level such that the output voltage drops 1.5 dB. 7. Switch the Limiter In. Slowly turn trimpot VR1401 counterclockwise until the output voltage drops an additional 0.2 dB. REAR-PANEL BOARDS AND COMPONENTS The following printed circuit boards and components are mounted on the rear panel. SHR-10 SHR-03 SHR-02 SHR-01 SHR-13 B1 S3 W1 J1 XF1 INPUT-OUTPUT BOARD AUX/MIC BOARD HI-Z INPUT BOARD LO-Z INPUT BOARD SPEAKER OUTPUT BOARD FAN +24 VDC PHANTOM POWER SWITCH POWER CORD AC CONVENIENCE RECEPTACLE EXTERNAL FUSEHOLDER

SHR-02 HI-Z INPUT BOARD To remove SHR-02, remove the six 1/2-inch nuts on the input jacks. Disconnect the four 3-pin connectors from the SHR-01 LO-Z INPUT BOARD and the two 3-pin connectors from the SHR-03 AUX/MIC BOARD. Pull the board straight back to disengage the jacks from the rear panel: SHR-02 can then be completely separated from the 1200. SHR-01 LO-Z INPUT BOARD Remove the twelve screws (two per input) connecting the XLR-type connectors to the rear panel. To remove SHR-01 without first removing SHR-02 HI-Z INPUT BOARD, remove the four Phillips screws that hold the rear panel to the chassis bottom. Rest the unit on its side while performing this operation. Then swivel the rear panel away from the chassis (it is still held by the power cord). This allows SHR-01 to be pulled straight back and away from the rear panel without being stopped by the interior vertical metal shield. Disconnect the four 3-pin connectors (two from SHR-03 and two from SHR-04 CHANNEL BOARDS) and the four 4-pin connectors (from SHR-02 and SHR-04). (Be sure to label all removed lead-connector assemblies.) Unsolder from point AA the yellow lead from SHR-10 REAR PANEL INPUTOUTPUT BOARD: SHR-01 is now completely free of the 1200. SHR-13 SPEAKER OUTPUT BOARD To remove SHR-13 SPEAKER OUTPUT BOARD: 1. Disconnect the 3-pin connector from P1301. 2. With a 1/2-inch nutdriver or wrench, remove the nuts holding the speaker output jacks to the rear panel. 3. Unsolder the leads from AA and AB. 4. The SHR-13 board is now free of the 1200. B1 FAN To remove the fan: 1. Remove the four screws, nuts, and starwashers at the four corners of the fan grille. This frees the fan from the rear panel. 2. Unsolder the black fan leads from pins AE and AG on SHR-14. 3. If necessary to remove the fan from the 1200, slide the fan leads out of the insulating tubing and separate the fan from the unit.

For access to or replacement of any of these parts, turn the 1200 on its side (power transformer down) and remove the four Phillips screws that hold the rear panel to the chassis bottom. The rear panel then can be separated sufficiently from the chassis bottom to permit access to these boards and components. SHR-10 INPUT-OUTPUT BOARD To remove SHR-10, use a 1/2-in. nutdriver to remove the nuts on the five phone jacks. Carefully pull the board straight back until the connectors are free of the rear panel. To separate the board completely from the rear panel, remove the 6-pin and 4-pin connectors from P1001 and P1002. Unsolder the green and red leads from the Phantom Power switch, and unsolder from SHR-10 the yellow lead that connects AC on SHR-10 to AA on SHR-01. SHR-10 can now be completely separated from the 1200. SHR-03 AUX/MIC BOARD To remove SHR-03, disconnect the four connectors from AA, AB, BA, and BB to P201 and P202 of SHR-02 and from AC, AD, BC, and BD to P102 and P104 of SHR-01. Remove the four Phillips screws that hold the switches to the rear panel; SHR-03 can be completely separated from the 1200. 7

CAUTION When replacing the fan, be sure to slide the leads through the insulating tubing before soldering them to the pins on SHR-14.

S3 PHANTOM POWER SWITCH Remove the two screws that fasten the Phantom Power Switch to the rear panel. This will free the switch from the panel. to separate the switch completely from the 1200, unsolder the red and green leads from the switch terminals. FRONT-PANEL BOARDS AND COMPONENTS The following printed wiring boards and components are mounted on the front panel. SHR-04 SHR-05 SHR-07 SHR-06 SHR-09 SHR-08 S2 CHANNEL BOARD (6) MASTER CONTROL BOARD HEADPHONES CONTROL BOARD HEADPHONES OUTPUT BOARD LIMITER BOARD INDICATORS BOARD POWER ON/OFF SWITCH

SHR-04 CHANNEL BOARD The SHR-04 Channel Boards are assembled and installed in pairs. Therefore, SHR-04s for Channel 1 and Channel 2 constitute one pair, those for Channel 3 and Channel 4 constitute another pair, etc. To remove any pair of Channel Boards: 1. Remove the control knobs by pulling them off the shafts. 2. Remove the two flat-head Phillips screws that hold the Channel Board Assembly in place. One screw is attached to the top of the front panel ledge, the other to the chassis bottom. 3. Disconnect the Channel Bus Connector from the top of each of the two Channel Boards. 4. Disconnect the 3-pin connector (coming from SHR-01 Input Board) from the bottom of each of the two SHR-04 Channel Boards. 5. Pull the Channel Board Assembly horizontally backward to free the control shafts from the front panel; the Assembly is now free of the 1200.

SHR-09 LIMITER BOARD To free SHR-09 LIMITER BOARD from the Mounting Panel, remove from the front of the panel the two Phillips screws that attach the Limiter Switch to the panel. This frees the board from the panel. SHR-06 HEADPHONES OUTPUT BOARD AND SHR-07 HEADPHONES CONTROL BOARD SHR-06 and SHR-07 are connected together by a solderedin-place 4-conductor ribbon cable. If it is not necessary to replace the cable, either remove both boards (if desired to free one of them completely from the 1200), or only remove one (if freeing the assembly from the 1200 is not essential). To remove SHR-07 HEADPHONES CONTROL BOARD, remove the 7/16-inch nut that holds the control shaft to the Mounting Panel. This permits the board to be freed from the panel (although it is still connected via the ribbon cable to SHR-06 HEADPHONES OUTPUT BOARD). To remove SHR-06 HEADPHONES OUTPUT BOARD, remove the 1/2-inch nut that holds the phone jack to the Mounting Panel. This permits the board to be freed from the Panel. SHR-08 INDICATORS BOARD Remove the two Phillips screws holding SHR-08 to the back of the Mounting Panel. Pull the board back from the panel to remove the LEDs from their holes and to free the board. S2 ON/OFF SWITCH To remove the On/Off Switch from the Mounting Panel: 1. Pull the switch button off the switch control shaft. 2. Remove the two Phillips screws that hold the switch to the panel. 3. Unsolder the red and black transformer leads from the switch. A1200MX INPUT EXPANSION MODULE The A1200MX is an optional input expansion module kit that provides two additional input channels to the 1200. A maximum of two A1200MXs can be added to the 1200 for a total of 10 inputs. The A1200MX consists of an input connector module (SHR-15 and SHR-16), an input transformer module (SHR-17), a channel control module (two SHR-04s), control knobs, and hardware. The A1200MX circuitry is identical to the input circuitry of the other six input channels. Servicing can be accomplished in the same manner. Printed wiring board drawings are provided with the service drawings. CHECKING ACTIVE COMPONENTS Integrated circuits can be checked without removing them from their circuit board. Measure the input, output and power supply voltages as shown on the applicable circuit diagram. Defective transistors and diodes can be located by use of a standard ohmmeter such as a Simpson 260. Polarity of the ohmmeter must be verified before these checks are made; all resistance measurements are made with the power off in the circuit under test. With a known diode orientation, measure the diode resistance in the forward and reverse directions. The lowest meter reading will establish the probe at the cathode end (schematic symbol arrow points to cathode) as the "minus" probe while the other probe will be "plus." (Some ohmmeters are not polarized in this manner with relation to "volts plus probe" and "volts minus probe.") With the ohmmeter "plus" probe on the anode end of a diode, and the "minus" probe on the cathode end, the ohmmeter should be read approximately 2000 ohms or less. With the meter probes reversed, a reading of about 10,000 ohms or more should be obtained. If either of these conditions is not met, one lead should be unsoldered from the circuit and the test repeated. If the results are identical, the diode should be replaced. 8

FRONT MOUNTING PANEL The Front Mounting Panel must be freed from the Front Panel in order to work on or remove SHR-05 MASTER CONTROL BOARD, SHR-06 HEADPHONES INPUT BOARD, SHR-07 HEADPHONES CONTROL BOARD, SHR-09 LIMITER BOARD, SHR-08 INDICATORS BOARD and the Power On/Off Switch from the 1200. To remove the Mounting Panel: 1. Remove the two flat-head Phillips screws from the front panel ledge above the Mounting Panel. 2. Rest the 1200 on its side with the fan and mounting panel upwards. 3. Remove the top three Phillips screws holding the front panel to the chassis bottom. Leave the bottom screw (below Channel 1) in place. (This will permit swiveling the front panel far enough away from the chassis to allow the Mounting Panel to be freed from the 1200 after other required disconnections have been made.) 4. Remove the knobs from the control shafts of the Master and Headphones Controls. 5. Disconnect the 3-pin connector from P701 on the HEADPHONES CONTROL BOARD. 6. Disconnect the 3-pin connector from P601 on the HEADPHONES OUTPUT BOARD. 7. Disconnect the CHANNEL BUS connector from P501 at the top of the MASTER CONTROL BOARD and disconnect 8-, 4-, and 5-pin connectors from P502, P503, and P504 at the bottom of the MASTER CONTROL BOARD. IMPORTANT: Mark all connectors before removing them so that they can be reconnected correctly. 8. Loosen the cable tie that holds the cable harness to the hole in the outside bottom of SHR-05. 9. Swivel the front panel away from the chassis bottom enough to permit pulling the control shafts out of the front panel and partially freeing the Mounting Panel from the 1200. (The panel is still connected to the 1200 by the transformer leads connected to the On/Off switch.) From this position it is possible to remove or work on boards SHR-05, -06, -07, -08, and -09.

SHR-05 MASTER CONTROL BOARD To remove SHR-05 MASTER CONTROL BOARD from the Mounting Panel: 1. Remove the control knobs. 2. Use a nutdriver or wrench to remove the nuts holding the control shafts to the Mounting Panel. 3. To free the board, pull the shafts back out of the panel.

To check LEDs, connect the cathode (notch or flat on flange, tab on lead or short lead) of the LED to the negative terminal of a standard 9 V transistor battery. Connect the positive battery terminal through a 4.7 k resistor to the LED anode. Replace any LED that does not light. CAUTION Do not check LEDs with an ohmmeter. The LEDs may be damaged or erroneous readings may be obtained.

FERRITE BEADS All low-impedance microphone connectors contain ferrite beads (L101-L112, SHR-01). Be sure to replace any ferrite beads removed during servicing. SERVICE ILLUSTRATIONS Immediately following the parts list on the pages that follow are printed wiring board foil and legend drawings, and circuit diagrams. Once a board has been located through the parts location photo (Figure 1), the components on that board can be located from the board drawing. The function of the part is shown on the relevant circuit diagram. OPTIONAL ACCESSORIES The following optional accessories are designed for use with the Shure 1200 AUDIOMASTER Powermixer. Carrying Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A1200C Input Expansion Module (2 channels, 2 each HI Z and LO Z inputs . . . . . . . . . . . . . . . . A1200MX* Speaker Cable, 15 m (50 ft), with phone plugs . . . . . . A50SC 240 V Conversion Kit . . . . . . . . . . . . . . . . . . . . . . . . . RKC209* Line Matching Transformer (LO Z to HI Z) . . . . . . . . . . . A95UF Phono Preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M64A

To check transistors, the ohmmeter should be set to the 100or 1,000-ohm scale. Transistors must be removed from the circuit before testing. If all conditions in the following table are met, the transistor may be considered free of any major defect; if any of the following conditions are not met, the transistor should be replaced. See Figure 3 for active component lead codes. OHMMETER CONNECTlON "Plus" Lead Collector Emitter Collector Emitter Base Base OHMMETER READING NPN PNP Transistor "Minus" Lead Transistor High High Emitter High High Collector Base High Low High Low Base High Collector Low Emitter Low High

*For installation by qualified service personnel only.

9

REPLACEMENT PARTS LIST
The following list provides information on replacement parts for the Shure Model 1200 AUDIOMASTER Powermixer. Shure part numbers are given for all parts and, where available, manufacturer's name and part number for acceptable equivalents in parentheses following the part description (note that for optimum performance, only direct replacement parts should be used). NOTE: Carbon film resistors shown in this parts list are rated at 0.2 watts. Standard 1/8-watt resistors should only be used as replacements if circuit power requirements are not exceeded. Standard 1/4-watt resistors can only be used if they are physically mounted in a vertical position. NOTE: In early production, PC Board Assembly SHR-14 contains the following legend error: Capacitor C1423 is marked "+" on the wrong lead. Note the position of C1423 and replace (if necessary) according to the part, not the legend. SHURE PART NO. 803039FK 802641FK 707471FK 707416FK 707425FK 707707FK 707725FK 707439FK 707424FK 800660FK 707351FK 707344FK 707328FK 707358FK 802602FK 707316FK 707350FK 708009FK 707629FK 707315FK 802600FK 707714FK 707571FK 707416FK 707705FK 707438FK 707329FK 707322FK 707354FK 802599FK 802605FK 800625FK 802594FK 800633FK 802596FK 802597FK 706541FK 802593FK 706306FK 706319FK 706323FK 706322FK 713642FK 802634FK 784129FK 802633FK 802629FK 713373FK 784104FK 784108FK 802625FK 788427FK 802579FK 802580FK 802581FK 802582FK

REFERENCE DESIGNATION A1 B1 C401, C702, C1405, C1408 C402, C410-C411, C413, C508, C509 C404 C407, C503 C408-C409, C501-C502, C1410 C412, C1411, C1415 C506, C510-C511, C1414 C701 C1006 C1101 C1103 C1104, C1113 C1105, C1107 C1106 C1108 C1109, C1112 C1110-C1111 C1201 C1301 C1401 C1403 C1406, C1412-C1414 C1407 C1417-C1418 C1419 C1420-C1421 C1422-C1423 C1424-C1425 C1426-C1428 D401-D404, D701-D702, D1401-D1418 D405 D801-D802 D803 D804 D1101 D1102-D1105 D1106-D1107, D1419-D1421 D1422 D1423 D1424 F1 F1401-F1402 F1403-F1404 J1 J101-J106 J201-J206, J1001-J1005 J601, J1301-J1302 L101-L112 L1101 MP1 MP2 MP3 MP4 MP5

DESCRIPTION Reverb Pan Fan Capacitor, Electrolytic, 0.22 µF, 50 V (Nichicon UKB1HR22KAA) Capacitor, Electrolytic, 22 µF, 16 V (Nichicon UKB1C100KAA) Capacitor, Electrolytic, 10 µF, 25 V (Nichicon UKB1E100KAA) Capacitor, Mylar, 0.0015 µF (Panasonic ECQ-B1H152JZ) Capacitor, Mylar, .047 µF (Panasonic ECQ-V1H473JZ) Capacitor, Electrolytic, 1 µF, 50 V (Nichicon ULB1H010MAA) Capacitor, Electrolytic, 4.7 µF, 25 V (Nichicon ULB1H4R7MAA) Capacitor, Electrolytic, 10 µF, 50 V (Nichicon ULB1H100MAA) Capacitor, Electrolytic, 100 µF, 50 V (Nichicon ULB1H101MPA) Capacitor, Electrolytic, 1 µF, 50 V (Nichicon ULB1H010MAA) Capacitor, Electrolytic, 47 µF, 25 V (Nichicon ULB1E470MAA) Capacitor, Electrolytic, 10 µF, 63 V (Nichicon ULB1J100MAA) Capacitor, Ceramic, 10 pF, 500 V Capacitor, Electrolytic, 22 µF, 16 V (Nichicon UKB1C100KAA) Capacitor, Electrolytic, 47 µF, 50 V (Nichicon ULB1H470MAA) Capacitor, Ceramic, 100 pF, 100 V Capacitor, Mylar, .1 µF (Panasonic ECQ-V1104JZ) Capacitor, Electrolytic, 10 µF, 16 V (Nichicon UKB1C100KAA) Capacitor, Mylar, .047 µF, 100 V (Sprague 225P47391WD3) Capacitor, Mylar, 0.0056 µF (Panasonic ECQ-B1H562JZ) Capacitor, Bipolar Electrolytic, 10 µF, 16 V (Panasonic ECE-A1CN100S) Capacitor, Electrolytic, 10 µF, 16 V (Nichicon UKB1C100KAA) Capacitor, Mylar, .001 µF (Panasonic ECQ-B1H102JZ) Capacitor, Electrolytic, 0.47 µF, 50 V (Nichicon UKB1HR47KAA) Capacitor, Electrolytic, 100 µF, 25 V (Nichicon ULB1E101MAA) Capacitor, Electrolytic, 1000 µF, 16 V (Nichicon ULB1C102MRA) Capacitor, Electrolytic, 470 µF, 50 V (Nichicon ULB1H471MRA) Capacitor, Electrolytic, 10,000 µF, 63 V Capacitor, Ceramic, .01 µF, 500 V Diode (RCA SK3100) LED, Red (RCA SK2022/3022) LED, Red (RCA SK2022/3022) LED, Yellow (RCA SK2021/3021) LED, Green (RCA SK2024/3024) Diode, Zener (RCA SK24A) Diode (RCA SK3100) Diode (RCA SK3311) Silicon Rectifier (RCA SK3647) Silicon Rectifier Silicon Rectifier Fuse, 5 A, 250 V (Littelfuse 312005) Fuse, 0.75 A, 250 V (Littelfuse 312.750) Fuse, 8 A, 250 V (Littelfuse 312008) Outlet, Unswitched AC Connector, XLR-type Receptacle, 3-pin (Cannon XLB-3-31PC) Phone Jack, 2-Circuit Headphone Jack, 3-Circuit Ferrite Bead Coil, 4.6 µH Rubber Foot Knob, Green, Bass Knob, Green, Treble Knob, Black Knob, Gold 10

REFERENCE DESIGNATON MP6 MP7 MP8 MP9 MP10 P1003-P1004 P1401 Q501, Q1110, Q1403 Q1101, Q1114 Q1102 Q1103-Q1104 Q1105,Q1109 Q1106 Q1107-Q1108 Q1111 Q1112-Q1113 Q1401-Q1402, Q1404 Q1405 Q1406 R101-R106 R201-R206, R405, R520, R522, R1404, R1415, R1445, R1452 R301, R304, R514 R302, R305 R303, R306, R407, R414, R416, R503, R513, R1401, R1412, R1423, R1426-R1427, R1430 R401, R518 R402 R403 R404, R409-R410, R502, R504, R512, R519, R602 R406, R408, R505-R506 R411, R1410, R1422, R1424, R1448-R1449 R412, R1006, R1409, R1420-R1421, R1433, R1435-R1438, R1443, R1446, R1451, R1458 R413, R1419, R1453 R415, R523, R601, R704, R1414, R1417-R1418, R1425, R1429, R1442, R1444, R1447 R501, R511 R507 R508, R515, R1428 R509, R516-R517 R510 R521, R1001-R1005, R1413, R1431-R1432, R1459 R603-R605 R701, R703 R702 R1101 R1102, R1104 R1103, R1112, R1201 R1105 R1106-R1108 R1109 R1110 R1111 R1113 R1114 R1115 R1116 R1117 R1118-R1119 R1120, R1122 R1121, R1123 R1124-R1125

SHURE PART NO. 802583FK 802584FK 802585FK 802587FK 802642FK 802628FK 711080FK 706102FK 706146FK 800412FK 802590FK 801798FK 706156FK 802591FK 706155FK 802592FK 706537FK 706139FK 706147FK 802610FK 801057FK 801059FK 801068FK 801065FK 802607FK 801075FK 801076FK 801061FK 801058FK 801081FK 801073FK 801072FK 801069FK 801062FK 801055FK 801077FK 801041FK 803041FK 801053FK 802614FK 802815FK 803042FK 708857FK 708842FK 708845FK 708835FK 708850FK 708906FK 708934FK 802617FK 803043FK 708838FK 708836FK 802616FK 802610FK 708849FK 708854FK 708840FK 802613FK

DESCRIPTION Knob, Red Knob, Blue Knob, White Fan Grille, Front Panel Fan Grille, Rear Panel Connector, Receptacle, 2-pin Connector, Receptacle, 8-pin Transistor, PNP (RCA SK3932) Transistor, Dual, NPN (RCA SK9427) Transistor, Dual, FET Transistor, Power, PNP (RCA SK9042) (requires 802681FK insulator) Transistor, NPN Transistor, NPN (RCA SK9118) Transistor, Power, NPN (requires 802639FK insulator) Transistor, PNP (RCA SK9363) Transistor, Power, PNP (requires 802639FK insulator) Transistor, FET Transistor, NPN (RCA SK9137) Transistor, PNP (RCA SK9138) Resistor, 1.8 K Resistor, 4.7 K Resistor, 6.8 K Resistor, 39 K Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, 22 K 2 K, 2% 150 K 180 K 10 K 5.6 K 470 K 100 K

Resistor, 82 K Resistor, 47 K Resistor, 12 K Resistor, 3.3 K Resistor, 220 K Resistor, 220 Resistor, 43 K (Early Production); 30 K (Later Production) Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, Resistor, 11 2.2 K Metal Oxide Film, 220, 1 W 13 K, 1% 680, 2% 47 K 2.7 K 4.7 K 680 12 K 1.8 K, 2% 47 K, 2% Metal Oxide Film, 5.6 K, 2 W Metal Oxide Film, 68, 1/2 W 1.2 K 820 Metal Oxide Film, 3.9 K, 2 W Metal Oxide Film, 1.8 K, 1/2 W 10 K 27 K 1.8 K Metal Oxide Film, 100, 1 W

REFERENCE DESIGNATION R1126-R1127 R1128 R1301 R1402 R1403, R1454 R1406-R1407 R1408 R1411 R1416 R1434 R1439 R1440, R1455 R1441 R1450 R1456 R1457 R1460 R1461-R1462 S1 S2 S3 S301-S302 S901 SHR-01 SHR-02 SHR-03 SHR-04 SHR-05 SHR-06 SHR-07 SHR-08 SHR-09 SHR-10 SHR-11 SHR-12 SHR-13 SHR-14 T1 T101-T106 U401-U402, U501-U504, U701, U1401-U1407 U1201 U1408 U1409 U1410 V1401 VR401 VR402, VR502 VR403, VR405, VR701 VR404 VR501, VR504 VR503 VR1101-VR1102 VR1103 VR1201 VR1401 W1 W2 W3 W4 XF1

SHURE PART NO. 802612FK 708853FK 710041FK 801064FK 801080FK 800190FK 801033FK 801085FK 801089FK 801063FK 802609FK 801070FK 801051FK 801045FK 800749FK 802611FK 709314FK 802615FK 802630FK 802631FK 802632FK 801599FK 784110FK 235901FK 235902FK 235903FK 235904FK 235905FK 235906FK 235907FK 235908FK 235909FK 235910FK 235911FK 235912FK 235913FK 235914FK 803474FK 802626FK 706077FK 802588FK 802589FK 706097FK 706098FK 802598FK 802620FK 802622FK 802619FK 802621FK 802623FK 802624FK 802618FK 802681FK 800030FK 710138FK 802638FK 908575FK 908580FK 800618FK 802636FK

DESCRIPTION Resistor, Ceramic, Dual, .22, 5 W Resistor, 22 K Resistor, Ceramic, 10, 5 W Resistor, 18 K Resistor, 390 K Resistor, 22, 1/2 W Resistor, 47 Resistor, 1 M Resistor, 2.2 M Resistor, 15 K Resistor, 51 K, 2% Resistor, 56 K Resistor, 1.5 K Resistor, 470 Resistor, Metal Film, 100 K, 1% Resistor, Metal Film, 36 K, 1% Resistor, Metal Oxide Film, 39, 1/2 W Resistor, Metal Oxide Film, 47, 2 W Switch, Voltage Selector, DPDT Switch, On/Off, SPST Switch, Phantom Power, SPST Switch, Slide, DPDT Switch, Slide, DPDT Printed Wiring Assembly, Lo-Z Input Printed Wiring Assembly, Hi-Z Input Printed Wiring Assembly, Aux/Mic Printed Wiring Assembly, Channel Printed Wiring Assembly, Master Control Printed Wiring Assembly, Headphones Out Printed Wiring Assembly, Headphones Control Printed Wiring Assembly, Indicator Printed Wiring Assembly, Limiter Printed Wiring Assembly, Input/Output Printed Wiring Assembly, Power Printed Wiring Assembly, Sensor Printed Wiring Assembly, Speaker Output Printed Wiring Assembly, Main Transformer, Power Transformer, Mic Input IC, Quad Op Amp (RCA SK3465+) IC, Thermal Sensor IC, Voltage Regulator (Motorola MC7824) IC, Voltage Regulator, Positive (Motorola MC7815) IC, Voltage Regulator, Negative (Motorola MC7915) Opto-Isolator Potentiometer, Log, 100 K Potentiometer, Dual, Linear, 50 K Potentiometer, Log, 10 K Potentiometer, Linear, 20 K Potentiometer, Log, 100 K Potentiometer, Linear, 10 K Potentiometer, Linear, 100 Potentiometer, Linear, 1 K Potentiometer, Linear, 47 K Potentiometer, Linear, 5 K Power Cable and Plug, 3 m (10 ft), 3-Conductor Channel Bus Cable, Ribbon, 8-Conductor, with Connectors Cable, Ribbon, 5-Conductor Cable, Ribbon, 4-Conductor Rear Panel Fuseholder

+ May not exhibit the low-noise characteristics of the original part.

12

BLOCK DIAGRAM

LEAD CODES

15

16

17

18

19

20

CIRCUIT DIAGRAM-1 (SHR-01, SHR-02, SHR-03, SHR-04)
21

22

CIRCUIT DIAGRAM-2 (SHR-05, SHR-07, SHR-08, SHR-10)

CIRCUIT DIAGRAM-3 (SHR-09, SHR-12, SHR-14)
23

CIRCUIT DIAGRAM-4 (SHR-06, SHR-11, SHR-13, SHR-14)
24