Icom IC-751A Service Manual page 54

SECTION 6 MAINTENANCE AND ADJUSTMENT
6-1 PREPARATION BEFORE SERVICING
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Detach the power cord and turn OFF the VOLUME/POWER CONTROL before performing any work on the transceiver.
Do not short circuit components while making adjustments.
Use an insulated tuning tool for all adjustments.
Do not force any of the variable components. Turn them slowly and smoothly.
Follow the instructions exactly. If an indicated result is not obtained, repeat the instruction until the correct result is
obtained.
Check the condition of connectors, solder joints and screws when adjustments are complete. Confirm that components
do not touch each other.
Confirm defective operation of the transceiver first when checking an out-of-service unit. Verify that external sources do
not cause the problem.
Use the correct tools and test equipment.
Remove the transceiver case as shown in SECTION 5-1.
Attach a 13.8V DC external power source to the power supply connector. Be sure to check the polarity.
For transmission problems, attach a dummy load to the antenna connector. For reception problems, attach an antenna or
signal generator to the antenna connector. DO NOT transmit into the signal generator.
Recheck for the suspected malfunction with the VOLUME/POWER CONTROL ON.
Check the defective circuit. Measure the DC voltages of the collector, base and emitter of each transistor.