Mortal Kombat Board issue, need help

dkbruiser73

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Hey all, I got a Mortal Kombat 4 with a Syncing problem. I switched another jamma board inthe cabinet and the monitor works like a champ. I know its the board but not sure where to go from here. Original dedicated cabinet with original harness and board. Checked continuity on the sync wire its good and i got 4.8 volts coming out of it. You can see most of the screen just keeps rolling left to right. Ive got the rolling up and down to stop. Any help would be awsome guys. Not a noob but im definatly no expert. lol
Thanks, Marc
 
you sure it's a sync problem and not an issue with the monitor holds?

if you got it to stop rolling one way, then I would say it's not the sync coming out the board, considering it's composite sync (loss of that sync would make it roll both vertically and horizontally)

for lack of a better way of describing it, the holds on a monitor can work fine with some boards one way and not with others. you have to essentially find the sweet spot, and it should work fine with any boards. that adjustment is so minuscule in scope that if it were even the slightest bit off it would cause rolling.
 
Well it didnt stop completely rolling up and down it still drags slowly up the screen but its not moving so fast i cant see the pic. the left to right rolling is really fast. could it be the voltage coming out of the board. its only at 4.8. im not sure what the votage sould be for sync.
 
your voltage at the board is only 4.8V?

read the PSU guide I made up in my sig, ensure you're getting 5.1V at the roms first. otherwise I would say your problem could potentially be you're using the wrong sync pin on your monitor... it could be hooked up to the positive sync when it needs to be on the negative sync.

take a picture of the video signal plug from your JAMMA harness that plugs into the monitor chassis. I'll know for sure then. :D
 
Follow the video ground trace backwards from the JAMMA edge and check for a blown surface mount zero ohm resistor.
 
thanks for the tips guys got home to late to try them out but i will check it first thing when i get home from work tomorrow.
 
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