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NO SOUND
during this test(but sound can be heard during Diagnostic Tests).
Check the sound-select inputs (pins 2 through 9 of U9) to see if they pulse
during Sound Test 01. Also. check the -12 V supply voltage on the CPU
Board. If this voltage is low (or AC ripple seems too high), perform the
following checks:
1. The gray and gray-green transformer secondary wires for 19.4 VAC.
2. The CPU Board filter capacitor C26 for -12 VDC.
3. The filter capacitor C26 for excessive AC ripple (over 0.75VAC).
If the previous checks did not isolate the problem, turn the Volume Control
for maximum output. Momentarily touch a powered-up AC soldering pencil
on the center tap of the Volume Control.
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DO NOT use a soldering iron over 40 watts. Note also that cordless
soldering irons will NOTwork for this test.
Hearing a low hum or a 'click' indicates that the power amplifier (Ul,
TDA2002),
the Volume Control, and the speaker are operating
satisfactorily, as is the sound circuit cabling. Not hearing a sound requires
repeating the test with the Volume Control turned part way down, to
determine whether the Volume Control is faulty. Also, check the cable
connectors for proper mating, and that no broken wires affect this circuit.
Test/Diagnostic Procedures 1-43