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TEST/DIAGNOSTIC PROCEDURES
(Continued)
SYSTEM 11C SOUND CIRCUITRY TESTS.
Testing of the System 11C Sound circuitry, including the Audio Board, is possible only after successful
completion of the System 11C Memory Chip Test.
Audio Board Test. The game program conducts a brief check of the Audio Board (0-11581) circuitry at game
Turn-on; the game program reports the test results by brief sounds, as follows: No sound
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Audio Board is
not operating, or a failure is affecting the sound circuitry (broken cable; dead amplifier; etc.); 1 sound
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system
OK; 2 sounds
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RAM problem; 3 sounds
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U4 problem; 4 sounds
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U19 problem; 5 sounds
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U20 problem.
NO SOUND DURING THIS TEST (but sound can be heard during the Diagnostic Tests).
Check the -12 V supply voltage on the Audio Board. If this -12V dcvoltage is low (or AC ripple seems too high),
perform the following checks:
1. The gray and gray-green transformer secondary wires for 19.4 V ac.
2. The CPU Board filter capacitor C26 for -12 V de.
3. The filter capacitor C26 for excessive AC ripple (over 0.75V ac).
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 NOT work
for this test.
Hearing a low hum or a 'click' indicates that the power amplifier (U1, TDA2002), the Volume Con- trol, 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.
ROLLERGAMES 37
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