Page 57 - WilliamsMidway WPC 91 Schematics 16-9289

Sound Board
I.No Sound.
Usually the AD7524 DAC is defective.
2. No Speech.
Most likely ,the 55536 CVSD,the TL084 Op-Ampor, the TL082 Op -Ampare defective.
3. The speech is distorted.
This is usually caused by a defective 55536 CVSD or a defective 74LS74 .
4. No music.
Most likely the YM3012 or the YM2151 are defective.
5. The volume level is too low and the volume control is not the problem.
Check the TL084 and TL082 Op-Amps .
6. No output at all.
The LM1875 Audio Amp is probably defective . The Audio Amp should have -26V on pin 3 and , +26V
on pin 5. Anything else indicates a problem. The Sound ROM or RAM could be defect ive. There
should be high pulses on the output pins of the Sound ROM and RAM . The MC3340 At tenuator can
also cause this problem.
7. The board. is dead.
There is probably no ±12V .Check F501 and F502.
Sound Board Beep Error Codes Upon Game Thrn -On:
1Beep = Sound Boa rd O.K.
2 Beeps = U9 Failure (RAM )
3 Beeps = UI8 Fa ilure (ROM)
4 Beeps = Vl5 Failure (ROM)
5 Beeps = VI4 Fa ilure (ROM)
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