MK2 intermittent distorted graphics/no sync

mecha

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I tried searching for this problem a few different ways on here and came up empty so I'm making a new post for it. :)

I dug my Mortal Kombat 2 board out of its storage box and after resolving the continuous "Custom Chip Bad" error I had since I bought it (it was dirty game roms) I hook it up again and now I have blocky text/distorted graphics. ----------- based on what I've read over the last few years this is probably attributed to a failing RAM.

I just had the game running for awhile and just as I was going to snap pictures to post here, the graphics cleared up. to be sure I powered it off and back on and now I'm back to having no sync again.

EDIT: the sync issue is in the JAMMA harness -- I plugged MK4 back in and the problem carried. blocky text is back however!

monitor is a U5000

pics of what it's doing:
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thanks. help me channelmanic, you're my only hope.
 

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this is embarrassing. the sync issue was H-Hold. I kinda suspected it but didn't mess with it. explains its intermittent nature, it was just barely off!
 
What does the CPU test show?

Are there any gouged trace on the bottom or top of the board?

Can you post a pic of the board?
 
all good. even ran a burn-in test, came up good every time.

I inspected the board last night, some of the little driver chips had pins folded over onto traces. I just cut the excess off the ones I saw. there's a few scratches on the underside, nothing monumentally bad, should I just run continuity checks on those to be sure?

board's at work right now, I've been getting my ass kicked the last couple weeks, today's my late start. lol

the graphic distortion where it's all blocky is usually a RAM issue right?
 
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I found some traces in the RAM (?) section that look pretty jacked up.

I took this with my phone, hope you can kind of see what I'm talking about.

mk2board.jpg


I'm going to assume I'll have to jumper these, I think the smallest wire I have though is 20 gauge. I need that REALLY thin stuff, god that would make my life substantially easier when doing this patchwork stuff.
 
You'll need to check them with a multimeter... they don't look like they are damaged, just scratched on the surface.

I'd like to see a pic of the top of the board. If it's the board I'm thinking of there will be a custom surface mount chip in the middle of the board - the DMA controller. If that's the case then I'd recommend reflowing it.
 
k give me a few, I'll pop the memory board off.

there's a few socketed CPU(?) chips and there's a surface mount one too. I reckon that's the "Custom Chip", but as I said after cleaning the 2 game rom legs that error went away.
 
Could be...

But UE13, the chip in the middle of the board could also cause that. Are you able to reflow it? That's an easy chip to learn with. ;)

RJ
 
har. I experimented with something like that on a dead KI board once. I wound up bridging all the traces together LOL

I don't have the tools for doing any surface soldering work.

can I glue that brown socket back together? or I guess I could find like a small clamping device to hold it tight... any ideas?
 
supposedly you could separate each pad with a razor blade though.... not something I wanna do however. trust me when I say it looks fine. lol

I'll try running it in my showcase, so I can poke and prod it and see what's going on.
 
I had one that looked fine, but when it was reflowed each of the pins down one side made a little 'tink' sound when reflowed. They were under tension... the other sides didn't make that sound and the board would do screwy things when you pushed on the chip. It needed reflowing even though it looked OK to the eye.

As for the broken socket... a new one is best but until then you can try putting a zip tie around it and something between the zip tie and socket to hold it in place.

RJ
 
I used a mid sized zip tie around the socket, and pulled it tight with my gerber tool. I dropped the board in sans the sound board into my showcase and it works perfect now.

now if I bring it back to my "MK" cab and it goes back to doing what it's doing, along with that bizarre bullshit it does with ANY monitor you put in it having the top inch of the screen brighter than the rest, then I'll know it's possessed and I need to burn the motherfucker.

thanks for the help, I hope this got it.
 
Worst case... remove the old socket and install a new one. It's real simple on those through hole PLCC sockets.
 
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