(Topic ID: 257962)

System 9 Sound / No sound help


By Tbirdmatt66SS

6 months ago



Topic Stats

  • 7 posts
  • 4 Pinsiders participating
  • Latest reply 6 months ago by Tbirdmatt66SS
  • No one calls this topic a favorite

You

Linked Games

#1 6 months ago

Hello.
with the -12v disconnected at 1J17, and the game is on, I get positive + 4.58 volts on the -12 v circuit at all points of it. The game plays just fine. With the volume pot turned up, it’s a very loud hum which reacts when I touch the sound input legs on U48. I have the sound card bypassed. When I activate SW2 sound diagnostic switch. I faintly here a sound file, airlock open, close, and the ahhhhhhhhhhhhhh sound. I’ve checked and checked for continuity and bad soldier joints and haven’t encountered any issues. All components are new except for a few resisters over by the 2002 transitor/amplifier.
At a loss.. game had been dead for 25 years. Before it finally died, the sound hum issue was present back then. There was acid damage in the reset section and I had to rerout some traces. Any help greatly appreciated.

#2 6 months ago

Theres also a volume knob in the cabinet near the coin door,did you try adjusting that?

#3 6 months ago

Yes. And I have bypassed it as well. No change.

#4 6 months ago

Sorry, but your description is unclear. Are you doing all of this with the -12 V disconnected?

Usually what fails most on the MPU board are the 1458 op amps. Second most common is the 10 uf cap that the sound line runs through.

#5 6 months ago

Forgetting that this is a system 9, not 11. Same things still apply. The speech you are faintly hearing is being generated on teh seperate speech board. Even bypassed you'll faintly hear the things generated on that card. The only sounds generated on the MPU section will be from the DAC chip.

#6 6 months ago

Is the volume on the speech board turned up? Someone had a similar problem a while back and that's all it was. I think he had speech but not music though.

#7 6 months ago

Hello to that replied....

The positive 4.58 volts on the -12v circuit was discovered with the -12v line disconnected at 1j17.

With the -12V connected and all things operational. Have Rottendog powersupply.

I have pins 3 and 4 jumpered together at 1j20 to keep signal from going to the sound card.

I have tested the ribbon cable for continuity, and it checks out.

I have replaced the 10uF cap. I had a hard time finding one. Any suggestions of a vendor for a new one?

99% of the IC chips on the board have been replaced. Game was dead for 25 years. Finally got game play restored. The sound had failed with the loud hum before the rest of the game packed up.

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