Time Pilot 84 - No sound

ManiN

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Hey all, I have a Time Pilot 84 PCB that works ok but doesn't have sound. I can hear light static, so I'm pretty sure the speaker and wiring is ok, I don't really have a way to test as it's the only working Konami board I have.

I looked at the schematic and poked around here looking at posts. I saw that in some cases a bad op amp was the cause. I looked at the schematic and see the LS174 feeds the amplifier, so I replaced it but no change. Would it likely be the amplifier chip, or other? Any other experiences out there with Konami no sound? Seems like a common problem but oddly there is few repair logs on it.
 
Yeah the dirty trick of running your finger across the pins of the amp is a good troubleshooting tip :)

But you also want to check the input and follow it back with a scope.
 
I wiped my finger across and did hear popping and interference. So I assume that means the amp is doing something?

No scope for tracing anything... Audio chip failure?
 
Verify if your PSU does -5V.
This potential is almost necessary with old integrated amplifiers.
regards.
 
well.. interesting twist. The guy who had the cab & board before me said he didn't have a sound issue.

When I received the cab, it had the PCB edge connector cut off and also the power supply wasn't performing correctly when hooked to the PCB (after replacement connector installed).

I have since put a switcher in, and also put on a 18/36 edge connector. Everything seems to check out except the sound. I'll verify the connections again, but I believe it's all in the right spots...

I checked the 12v at the board quickly the other day and it showed 16v, this didn't seem right, but I of course had to leave right as I probed it, so I really need to do it again and double check that.
 
looked closer and I'm not sure how I saw 16v, but it's more like 13v. Also the other respective voltages are correct and on the right pins. When rotating the volume pot I can hear static, and also again on the amp when touching the pins you hear humming.

I did see an empty socket at I think J6 on the main PCB. Tried to look at the roms for the mame zip and it didn't show a chip but also there are many more than what that list showed...

Just frustrating as there is no sound produced whatsoever. no garble, no whisper, nothing.
 
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