Mortal Kombat 2 Board issue

Cobolisdead

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So, I am restoring a Mortal Kombat 2, and de-converting it from Rampage World Tour. Everything is almost done, but Player 1 Down does not work. At first I thought that it was just an issue with the connection between the switch and the PCB, but last night I was able to confirm that the signal is reaching the PCB. So that leaves me wondering, where do I go from here? I know that signal is getting to the PCB by testing the continuity between the Switch and the pcb connections. Also, this is the the only thing that I can't get working, as all the other inputs work correctly. Any help here would be greatly appreciated.
 
there's a number of chips that drive those inputs. trace from your suspect switch at the JAMMA edge, follow the trace to whichever chip it runs to. chances are that's your culprit. I've never had the problem myself so I don't profess to be an expert on such matters. :p

my only other advice is to read my PSU guide: clean your JAMMA edge and make sure your power supply isn't set extremely high cause that's how you burn chips out. MK2 you can probably get away with setting your power supply between 5.20-5.25, but that's a your mileage may vary thing. you're looking for about 5.10V to the chips.
 
I checked the voltage, and I am getting 5.02 out of the switching power supply.
 
So, I am still working on this issue.

I can get the game to run, still no player 1 down though, by lowering the voltage to around 5V even. Whenever I do that though, player movement sometimes goes out altogether and the attacks sometimes don't work either. Also, for some reason the monitor colors look off a little for some reason. Why would the power adjustments affect that?

When I get the power level up again to around 5.10v, I get a bad rom error on uj12. So I thought I would order the new set of rom revisions off of ebay to see if that fixes the issue.
 
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