User MVS MV-1FZ with sound issues

[RenierD]

Good day all

I've learnt so much on these forums, thank you, so I hope you can help.

I'm in the process of troubleshooting a sound issue on a used MV-1FZ board.

So far:

• Power is connected and the games are playing correctly

I've read that you can output mono sound using the JAMMA - which is my first goal. I'm using the Jamma edge + and - to a single speaker, but the sound is horrible (sound file attached - zipped). On closer inspection, it looks like the amp chip (OPAMP1) was replaced, or at least resoldered (img attached). It seems like there used to be a blue jumper wire between pin 3 and pin 14 (broken off at the moment).

The onboard volume control seems to work. I have it on the lowest level.

My questions:
1) Can I use Jamma edge for mono sound (+ and -) or should I be approaching sound differently on this board?
2) Am I correct in assuming the, or at least a sound problem lies with the amp chip?
3) What would the bridging of pin 3 and pin 14 be for?

Troubleshooting so far:

• No (other) visible/noticeable problematic components
• Horrible sound the same on different carts
• Jamma harness and games sound normal on MVS-1C board
• Cleaned Jamma connectors
• Removed glue (for what it's worth)
• Brushed board

Thank you so far

 

[Neo Alec]

The condition of that amp looks really bad. I would replace it and clean it up. Your problem could still be something else in the sound circuit, like the DAC or caps.

Mono sound from the jamma edge is the normal way to use that board in cab. If consolizing it or using the board on a supergun, I would stereo mod it.

 

[RenierD]

The condition of that amp looks really bad. I would replace it and clean it up. Your problem could still be something else in the sound circuit, like the DAC or caps.

Thank you

Lets start there.

First time for me. I see now that it was pins 5 and 8 that used to be connected, and not 3 and 14 =p. (Edit: nm, I'm not sure now).

Any suggested suppliers? I get links from Alibaba and AliExpress. Are they worth it? eBay or other links would be appreciated.

 

[RenierD]

Mono sound from the jamma edge is the normal way to use that board in cab. If consolizing it or using the board on a supergun, I would stereo mod it.

Is that chip controlled by the volume knob?