Jamma harness - no audio

jay

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I started working on a cab I've had for a while. After finding a short in the power cord, I got her up and running but I have no audio.

I've tried 2 boards that I know work. I've changed the speaker, adjusted volume pot and checked in the "service" menu of both that the sound is on.

I've also traced the wires back to the connector pins and they are correct. I'm assuming it's a bad connector on the harness.

Any idea what kind of voltage I should be getting on the audio/speaker pins? I assume it will be minuscule but I'd like to troubleshoot further.

Hopefully, I'm just fogetting something obvious.

Thanks
 
is the -5v wire present in the harness?

Shit!! I think I remember looking at that and noticed it was missing. I'm not home right now, but I'll check and report back.

Thanks man.
 
Hmmm. I checked my other jamma machine and I do not have -5 connected. The 2 boards that I have tested have sound in that machine.

I've also looked at a schematic on the jamma pinouts and I don't see a -5 connection.
 
Do you have 12V at the board? Without that the amp will be powered off.

If the boards are known to be good then the only things the cabinet will contribute to the audio system is 12V for the amplifier chip, -5v if the game needs its, the speaker(s) and two wires.

It is worth checking how the speaker wires connect to the harness. One side of the speaker should connect to pin 10 and the other side to the the pin directly underneath pin 10 on on the solder side, I have seen some cabinets where one is wired to ground and the other is wired to pin 10. The amp on the board may not like this if that is the case.
 
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check for continuity from both ends of the speaker wire (at the speaker and at the edge connector) for both wires with your multimeter with the game off. this will tell you if there's a short in the line.
 
Do you have 12V at the board? Without that the amp will be powered off.

Winner!

I had 11.80v coming out of the power supply. I tried to adjust it/crank it up a little, but it wouldn't go any higher. The 5v would adjust though.

Swapped the PS after that and I have sound now.

Thanks to all for the sugestions and help.
 
Yes 11.8 V would have been fine, these audio amps are happy with anything between 9V and 21V usually, with 12V being the stated ideal.
 
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Winner!

I had 11.80v coming out of the power supply. I tried to adjust it/crank it up a little, but it wouldn't go any higher. The 5v would adjust though.

Swapped the PS after that and I have sound now.

Thanks to all for the sugestions and help.

You would be surprised at how many different issues I have fixed with simple multimeter and power supply fixes.
 
Yes 11.8 V would have been fine, these audio amps are happy with anything between 9V and 21V usually, with 12V being the stated ideal.

That's what I figured, but I thought "Ah, what the hell" and swapped it just to see.
 
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