Mortal Kombat 2 repair

xodaraP · May 6, 2018

A friend sent me some boards to repair, first one I've finished is one of 2 MK2 boards

Fault: All RAMs reporting bad, colours messed up, reboot loop

Fix:
Colours fixed by installing jumper between UB5 and a via it is supposed to be connected to, there was a lot of corrosion in an area of the board, so this was the likely cause. This pin is the activation pin for the colour RAMs

Everything else fixed by desoldering F253 and F04 at UD6 and UD7. I sanded back the board to expose clean copper, tinned the wires, replaced traces from a via to UD5 (VSYNC timing line), R69 to pin 2,3,5,7,9 of UD7 (all of these pins are grounded via this resistor) and a trace from a via to UD6 carrying the /RAS signal.

Tested by allowing attract to run for a while, all diagnostic tests pass and played some games. Love to see an MK2 back working again!

PascalP · May 6, 2018

Nice job, but....

xodaraP · May 6, 2018

Your wish is my command @PascalP

This is the screen the board presented with - all scratch RAMs reporting bad (I had already fixed the colour RAM issue by this stage)

The corroded area of the board, likely mouse pee, nice.

After cleaning up and tinning all the traces, it now looks like this - I lost 3 pads on UD6 when I removed the IC, the plated through holes were black from corrosion. Fortunately these pins were not connected on the top of the board and the bottom pads were fine. I don't have a photo from after I replaced the traces.