Mortal Kombat 3 and Ultimate MK3 PCB U1 Issue Possible Solution

itobandito

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Mortal Kombat 3 and Ultimate MK3 PCB U1 Issue Possible Solution

Hey gang, just wanted to share an issue and possible solution to an issue I was having with my MK3 PCB. During the pcb diagnotics test screen I was getting a issue with the U1 chip which from what I can tell is one of the main cpus used for the games sound. This is a chip with about 2 dozen legs mounted on the actual PCB on each side of it, it is not socketed.

Anways just wanted to share that the U1 might not be the actual problem. The problem may in fact be with some of the socketed sound roms on the board. I figured this out by putting ALL of my MK3 game roms on to UMK3 PCB that I know was working prior to doing the swap. Sure enough the working PCB now gave me the U1 error in the system diagnostics test. I swapped in the sound roms that were previously on the working board UMK3 board with my MK3 roms and sure enough the error was no longer there. These sound roms are easy to locate as they are above the regular game roms, I believe there are 3 or 4 of them and they are labeled music/speech etc.

Anywho, I hope this post helps someone in the future, it's definitely worth looking in to swapping/getting new sound roms before junking your PCB due to a bad U1 diagnotics message.
 
I don't know much about the Wolf units, my UMK3 works and I'm glad for that, but given that this was the first time they started producing games without independent sound boards, I think one of those roms is an actual software rom for driving the sound section (which you can see on the game's POST screen) and it's possible that it's the one that's bad.

read the number sequence of the rom banks (the U numbers) for the sound roms, whatever the lowest one is (first rom in the set?) may very well be the suspect chip. try swapping one chip at a time until you get the problem to carry over.
 
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