SHURE 1200
Service Manual

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