(Topic ID: 214865)

Constant background sound on Fireball Classic even in attract mode?

By action76

3 years ago

Topic Stats

  • 8 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by dothedoo
  • Topic is favorited by 1 Pinsider


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#1 3 years ago

I acquired a FBC not to long ago and just got around to shopping it out and getting it running again. It looks very nice and seems to be playing fine but there is one thing I'm curious about. There is a pulsating type of background sound that plays constantly, even in attract mode - very annoying. Is this normal? I wouldn't think it was supposed to play in attract mode. If so, is there anyway to turn it off? I have found the service bulletin about dip switch 30 but it does not seem to make a difference. Any suggestions?

#2 3 years ago

If background sound starts at the MPU power on PIA test and never stops, its usually a connector problem. The sound board (can) get stimulated during the power on test and then should be shut up when attract mode hits. If it does not, I'd focus on connectors first. If your solenoids are all working properly, then check the male headers on the sound board.

#3 3 years ago

Is that an actual system sound playing or are we talking about noise or static? If the latter that might be coming from a cable or bad cap on the board.

#4 3 years ago
Quoted from barakandl:

If your solenoids are all working properly, then check the male headers on the sound board.

Ok, thanks. I will check those this evening and see what I find.

Quoted from BigAl56:

Is that an actual system sound playing or are we talking about noise or static?

Yes it is the "Wha wha wha" background sound that is supposed to play during the game.

#5 3 years ago

Upon closer inspection, after taking the board out to examine the headers, it appears that the cap at C10 is bad. Could that possibly be the culprit of the constant background sound?

#6 3 years ago

C10 is a tantalum bypass on the 12v supply. Not likely to be the cause of a problem, but should be fixed. Instead of using a tantalum cap, install a 10uF 25v+ electrolytic cap. It can deal with the ripple and not explode in a fireball like the tantalum ones do.

On the schematic drawing in the bottom left corner you will see the inputs from the computer board. They are labeled "SOUND-SEL" When the game is in sound test or solenoid test with a logic probe check to make sure all these sound selects are changing states. You can go right to the 6803 chip and check there.

NOTICE how two of the sound select pins sneak off into the reset section. I am not sure exactly what Bally is doing there, perhaps waiting for the PIA power on test to reset the board fully? Anyways if Q6 is shorted it would force a sound select HIGH and make the sound board play wrong sounds.

#7 3 years ago

Well, I replaced C10 and C22 because I read that C22 is also on the unregulated 12V supply and has a tendency to go bad or explode. C22 did seem to be shorted when I tested it. I figured I would give it a whirl in the machine to make sure it was still functioning as good or better than it was before I replaced those. Lo and behold, replacing those two caps seems to have fixed the constant background noise. Yahoo! Thanks for everyones help.

#8 3 years ago

Nice! Thanks for posting the fix.

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