Mortal Kombat 4 - Input issue (Fixed)

[BuddyC]

Calling all Midway experts!

Got a weird issue with my MK4 PCB (Revision 3)
All tests show up green. Picture is stable and everything runs great except button 1 won’t register. Not in test mode and not in the game. All other buttons work great. Zero issues except for button 1 that does not work.

Tested on Astro City cab and 3 different superguns. Zero issues with other games from Midway (MK, MK2, NBA Jam etc)
Cleaned contacts etc etc...

Help?

 

[BuddyC]

After some tracing with my multimeter, I found the culprit.


Two 221 ohm resistors was way of spec. Replaced them with some new ones and everything works.
Those fuckers are tiny!
Happy game!