Tron sound issue

andrewuts1

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Just hooked up a new arcadeshop power supply adaptor in my tron and I lost sound. During game play now I get this "popping sound" when I shoot. My fuses are fine and the little 12v LED light is on on the adaptor. When I first hooked it up and was adjusting the power supply there was terrible "static noise" for a short period of time before no sound. I briefly got sound today when I put the pcb back in the game after testing it in another cab. It sounds fine in the other working cab. I also tested the audioamp in a known working cab and it is still fine. My 5v is set at 5.1 measured at the pcb. Any ideas? Thanks, Andy
 
My 5v is set at 5.1 measured at the pcb. Any ideas? Thanks, Andy

Where on the 3 board sandwich did you measure this voltage? Right where it comes in on the CPU board, or on the SSIO board itself?

You should try taking a voltage reading across one of the 100uf caps (big electrolytic ones) on the corner of the SSIO board farthest away form the ribbon cable interconnects.
 
tron sound issue

I tested it on the board closest to the middle portion of the cabinet. Still have no sound or a "popping sound" when shooting.
 
tron sound issue

Bumping this to the top hoping someone has a suggestion for me. I can faintly hear the game sounds during play but is definetly a poppong sound when shooting. Have two machines so I have a known working pcb and audioamp as well as ps (arcadeshop adaptor with switcher) and +5 is set at 5.1v measured at the board set.

Could this be a volume pot that's gone bad, a blown speaker? Anyone? Thanks, Andy
 
Could this be a volume pot that's gone bad, a blown speaker?
Seems unlikely. You said you have two machines, so exchange parts to identify the problem. I suspect the problem is on your PCB sound board. Move the PCB to the other machine and verify the problem travels with it.

Bumping this to the top hoping someone has a suggestion for me. I can faintly hear the game sounds during play but is definetly a poppong sound when shooting. Have two machines so I have a known working pcb and audioamp as well as ps (arcadeshop adaptor with switcher) and +5 is set at 5.1v measured at the board set.
Sound is generated by the AY8910s (F6/F7), mixed with the opamps (C10/E10), then amplified with the lm3900 (D3). All of this can be disabled with a mute line around C131 feeding through D107/D103. There's a very detailed section describing this in the MCR Troubleshooting guide (see here).

There's an MCR sound test rom (see here) available that can use to generate sound and trace the circuit with an oscilloscope. Since you heard a nasty static noise my wild-guess is that the amplifier died; if so then socket-and-replace the LM3900. Since you hear faint sounds my other wild-guess is that your mute line is broken.
 
tron sound issue

I put the pcb in the other working machine as I did with the audioamp and ps one by one and everything worked fine in that one. I was thinking maybe the volume pot might be bad. Another klover who's problem sounded similiar to mine suggested changing the connector that attaches to the sound portion of the pcb from the audioamp. Any other ideas or do you think that sounds reasonable? I did think I might try swapping volume pots next. Andy
 
Volume pot is easy to check -- one leg is +12v, one leg is ground, the other leg is a voltage that varys from 12v-0v depending on the position of the pot. Use your DMM on the SSIO board to check that the voltage is varying.
 
Do you recall where these test points are? They are on the outermost pcb? I just follow them from the volume pot to the pcb?
 
The volume pot has three legs on the back and is mounted in the coindoor.

Alternately it might be better to measure right on the SSIO board. This is only possible if you've unfastened and loosened the wiring enough to connect the board outside the machine while you're working on it. You can probe the backside of J3 while it's connected, or the large silver pads adjacent to J3 for unpopulated VR1, or the wiper on one side of R153.
 
Thanks to all that helped. My problem ended up being a corroided male molex connector that plugged into j4 on my new power supply adaptor. Cleaned it a bit and reseated it and I now have normal sound. Andy
 
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