MKII No Sound and Burning Smell

Kyrosfear

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Gentlemen,
I have a Mortal Kombat 2 that was working perfectly. I turned it on today and made it through approximately 2 minutes of gameplay before the sound abruptly ceased. My control panel was not latched so I pulled it up to check if the LED on the sound board was still on (which is view-able from that angle and it was still on). I immediately smelled electronic burn. I put a test PCB in the cabinet and everything worked fine. This narrows the problem to the sound board, which has a residual electronic burn smell still coming from it. There are no traces of burn on the solder side of the board, so I am looking for a place to start. I have read on forums regarding similar issues that this is typically due to bad caps or resistors. Can anyone tell me a good starting point? Thanks guys.
 
got any pictures of the sound board? (high res if you can so we can really pick it apart)

did you check your wiring from the main pcb to the soundboard? (maybe you had a short or high current melt one or more).

do you have original wiring from the main pcb to the soundboard? DIY? well made repro? soldered on speaker wire?

did you get sound from the board you put in place of your mk2 board? (just wondering if maybe the speaker shorted out somehow).
 
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Excellent questions, and thanks for the help.

I did check on the ribbon from the main to the sound. It is original, and looks fine.

The sound from the test pcb board I used worked fine.

I have attached A picture of the MKII sound board, and if it helps, the smell is most potent around the heat sink area.

The close up is of the caps under the heat sink.

I took several other pictures, but the forum keeps giving me an "upload of file failed" message for them.

Sorry no hi res, I only own cheap modern cameras.
 

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Excellent questions, and thanks for the help.

I did check on the ribbon from the main to the sound. It is original, and looks fine.

The sound from the test pcb board I used worked fine.

I have attached A picture of the MKII sound board, and if it helps, the smell is most potent around the heat sink area.

The close up is of the caps under the heat sink.

I took several other pictures, but the forum keeps giving me an "upload of file failed" message for them.

Sorry no hi res, I only own cheap modern cameras.

you have the heatsink correct and just removed it for the pictures i hope.

as for your upload issue, resize the picture down a bit, there's a file size limit so the smaller you can make the file in megabytes the better.

those caps look fine but your amp chip might be frying

what do the power wires look like from the main to sound board?

since the sound on your test board worked that rules out the cabinet wiring pretty much 100% (+1 for doing that in the first place, it's a great way to find out if it's something in the cabinet or your board).
 
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I had this EXACT issue and C2 was fried. I replaced it but it didn't help. Still nothing, but I had so many extra, I didn't troubleshoot further. If I had that board in front of me, I might be able to help further, but alas, I do not. Sorry.
 
Correct, I did just remove the heat sink for the picture.

Which one is the amp chip?

The power wires are fine all the way to the main.

As a rookie, a test pcb is an essential component for diagnostics. Otherwise I would be completely lost.

ZENOMORP- Did your C2 look bad, because all of my caps look fine.
 
My diagnostic run at startup shows greens across the board as well.
 
The rom check at startup doesn't check the sound roms. Only the main board. My C2 blew up. It was quite obvious.
 
The amp chip would be the one that's heatsunk silly :) And i'm going to take a wild guess the smell is coming from that area because it's toast now. Get the numbers off the chip and hit Google for a replacement

- Matt
 
So, would it be best to replace all of the caps on the board as well as the amp chip, even though the caps look okay?
 
So, would it be best to replace all of the caps on the board as well as the amp chip, even though the caps look okay?

Damn. I just realized that you are in Emporia. I'm in Wichita. I have an abundance of extra MK2 sound boards. You can have one for free to steal parts from or just use flat out if you want. Just say the word.
 
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