Shure AUDIOMASTER 1200, Service Manual

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PRINTED CIRCUIT BOARD AND PARTS LOCATION
FIGURE 1
W A R N I N G
CAUTION
After replacing high-voltage parts such as the fan, power
cord, rear panel convenience receptacle, or printed wir-
ing 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
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 screw-
driver 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.
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.
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