SOUND BOARD DIAGNOSTICS
SYMPTOM TEST & PROCEDURES
CHECK ROM BOARD OUTPUTS
(1)
If you hear game sounds, disconnect and reconnect sound board connector 10P3/J3.
(2)
You Should hear one or more game sounds. If so put the game in
Diagnostic Mode
Test 4 and proceed with this checkbox. If not go ahead to POWER SUPPLY checkbox
below.
TEST TOOL CONDTION & REMEDY
ROM board connector
2P4/J4-2 to 7
logic probe (game on and
in test 4)
•
PULSING - Repair cable to
sound board.
•
ANY LOW - Replace jack or foil,
proceed.
9C DIP resistors 2 to 8 VOM - Reading ohms
(game off)
•
ALL 4.7K - Proceed.
•
ANY OPEN - replace 9C.
C40-53 VOM - Reading ohms
(game off)
•
ALL OK - Proceed.
•
ANY SHORTED - replace bad.
MISSING SOUNDS:
NO SOUND--STEP 2
(ASSUMPTION
OFF-BOARD
FAILURE)
8C-10 to 15 (PIA) logic probe (game on and
in test 4)
•
PULSING - Proceed.
•
SOME LOW Replace 8C.
NO SOUND
(ASSUMPTION:
POWER SECTION
FAILURE)
CHECK ON-BOARD POWER SUPPLY
(1)
With power off test for fuse continuity at F1 and F2.
(2)
With power on check for +12v unregulated DC at TP1 and pin 5 of IC1.
(3)
Now check for +5v regulated DC between TP4 and TP3. If voltages are absent or low
turn off game and lift one pin of filter capacitors C25, C26 and C27.
(4)
Check each with ohmmeter for possible short circuits.
(5)
If capacitors are good and unregulated voltages test okay but you’re missing +5v,
replace regulator chip (IC8).
STILL NO SOUND
(ASSUMPTION:
AUDIO SECTION
FAILURE)
CHECK AUDIO (ANALOG) SECTION
(1)
Turn power on; turn up volume control. Momentarily place powered-up AC soldering
pencil on final amplifiers input pin (IC1, pin 1 or 10P4, pin 2) If you hear low hum, audio
IC, volume pot and speaker are okay.
(2)
Repeat test at Q2 emitter. If you hear hum, analogue section is okay. Step (1) will also
work if you simply touch amplifiers input pin
. However output level of hum will be much
lower than with soldering iron.
DO NOT use a soldering pencil over 40 watts. Cordless
models will NOT work here.
MISSING SOUNDS;
NO SOUND
(ASSUMPTION:
DIGITAL
FAILURE)
CHECK SOUND ROM 12 AND RELATED CIRCUITRY
(1)
Turn power on.
(2)
If you have no game sounds but power supply tests show normal voltages and no ripple
on +5v, check crystal clock circuit. Using DVM or logic probe, test for pulsing AC across
crystal. If clock signal’s absent replace crystal and associated capacitors.
(3)
Turn off power.
(4)
Swap sound ROM (IC12) and microprocessor chip (IC9) with known-good chips.
(5)
Power up and test Sound Board after each swap by pushing DIAGNOSTIC button.
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