Basic HTML Version
TEST/DIAGNOSTIC PROCEDURES
(Continued)
SYSTEM-11 SOUND SECTION TEST.
Press the Sound Diagnostic Switch (SW 1) on the CPU Board. Listen for the sound. The sound repeats,
until the operator turns the
HIGH SPEED
game Off and On.
NO SOUND DURING THIS TEST{but
sound can be heard during the 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 18.7 VAC.
2. The CPU Board filter capacitor C26 for -12 VDC.
3. The filter capacitor C26 for excessive AC ripple (over 0.7SVAC).
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.
©&'!w'lJ'U@!NJ
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 indicates that the power amplifier (U1, TDA2002), the Volume Control, and the speaker are
operating satisfactorily.
Not hearing a hum requires repeating the test with the Volume Control turned part
way down, to determine whether the Volume Control is faulty.
•