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Help With Mortal Kombat 1 T Unit Corrupted sound effects

Evan

Evan

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Hello,
I recently got this mortal kombat board, and while the game works well, and it says all the sound hardware is working perfectly in the test menu, the game has an issue with corrupted sound effects. Either a sound effect is corrupted, doesn’t play, or other random sound effects play when they shouldn’t be. The board is getting 5.16V and -5.52V. Any idea on a fix?

Video of issue
 

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OK, when you power it up, how many bongs do you hear? Just one?

When you turn the test mode DIP on and go into the sound tests, what sounds / effects do you hear OK? Which are bad?
 
I just came back to it and now it doesn’t even boot and just resets itself which is great
 
channelmaniac said:
OK, when you power it up, how many bongs do you hear? Just one?

When you turn the test mode DIP on and go into the sound tests, what sounds / effects do you hear OK? Which are bad?
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ok now when I boot it up I get no bongs at all. Here is an error at the test menu. Any ideas what it means?
 

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you have a communication failure. if you haven't replaced the caps on the sound board or the ribbon cable's wires have come detached from the housings one of these scenarios may happen: 1) the old caps leak/outgas, the latter can destroy chips if the chemicals spray on the legs (your picture, while not close up on the sound board, does not appear to have had this happen) 2) the old caps are just bad and don't work as they should anymore (this is anyone's guess what happens then!) 3) you have a broken connection via the ribbon cable or it's connected backwards on CPU or sound board ends (this doesn't appear to be the case, but ensure the red stripe of the cable is aligned with pin 1/2 markings on both boards) 4) you have a fault in the power harness that connects the JAMMA power to the sound board. the grey wires are +5V, you can measure voltage to the sound board at the grey (+5V) and black (ground) wires through the top of the power plug. it will probably be kind of low, 4.8xV so don't be alarmed, they still work fine. if you're missing that voltage then the sound board isn't thinking at all. also for posterity Mortal Kombat, NBA Jam/TE, Total Carnage, and Terminator 2 do not use -5V. :)

I've had success fixing ribbon cables to Williams pinball games by just inserting the housing ends in a vise and squishing it tighter. if you have the CPU and sound boards out already you can just continuity test the pins between boards to verify all the ribbon cable connections are there.

I have provided what I would argue to be a pretty comprehensive list of things to try. I may need to expand my sound board page.
 
I share my experience on the MK1 PCB if it can help (the sound test and "bong" was flawless). After a short time of play, the sounds was disturbed and didn't match the action. I burned and replaced the sound ROMs and the problem was fixed.
 
Neo.raizo said:
I share my experience on the MK1 PCB if it can help (the sound test and "bong" was flawless). After a short time of play, the sounds was disturbed and didn't match the action. I burned and replaced the sound ROMs and the problem was fixed.
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oh yeah I forgot if the U3 rom is bad, that will make it not work too. imagine if you will it's like you have a sound card in a computer, but no drivers. you will thus have no sound.
 
Ok now that i can work on it again the first thing I am going to try is to reflash the sound roms. Just reflash u3, u12 and u13?
 

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I'll try with other eproms instead, just in case something goes wrong… and to preserv originals.
 
I have not programmed any eprom chips before. What are the materials I would need? Also if anyone on this forum already has the ability to do it, maybe I can just get a hold of them and pay them to make me a replacement?
 
VodkaGobalsky said:
I have not programmed any eprom chips before. What are the materials I would need? Also if anyone on this forum already has the ability to do it, maybe I can just get a hold of them and pay them to make me a replacement?
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There are probably other users who have stock on hand, but in the very off event you can't find someone, I'm more than happy to program you a new rom if you provide the chip.
 
Okay I was told it's U13 or U33 that's possible broken, not the eprom. The custom DMA chip, is that even possible to be replaced?
 
U33 almost never fails. It will most likely need to be reflowed. I can do that for you.

U13 is on the sound board and is a sound ROM. U33 is the Custom DMA chip on the main board.
 
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