This repair post will span over two separate parts. Part #1 covers these three pinball machines and an NBA Jam Tournament Edition.
All of these games hadn’t had attention in some time. All three pinball machines had corrosion damage from the batteries. One of them was marginal enough to clean up the corrosion properly, put on NVRAM, and move forward. The other two I opted for new CPUs. All of them needed extensive repins in the switch matrix sections from the corrosion. I also took the driver boards back for all three and rebuilt, reflowed, and tested them. Across the three, several needed male pins in the GI circuit, and I believe all three needed female connectors repinned on at least one of the three GI related connectors. The T2 had a badly heat stressed DMD controller board, which I opted for the DMD HV daughter board that piggybacks the HV section of that board to remedy.
NBA Jam wouldn’t boot at all and had low voltage to the board which was able to be adjusted. Once up, the monitor came on, but it was all sorts of wonky. I took the K7000 chassis back with me, reflowed, recapped, cleaned up the power supply area that is always heat stressed on these, replaced the flyback as it was white knobbed style, and replaced the filter cap. There was still wonky vertical issues. It turns out the LA7833 vertical IC had failed. Once replaced, this was all good to go.
As a segue into part #2, there is a Mortal Kombat II. It had a weird vertical tear in the center of the monitor that couldn’t be adjusted out. I brought the K7000 chassis for it back as well and reflowed, recapped, cleaned up the power supply, and replaced the filter cap. The vertical tear was still there. I swapped C51 which isn’t in cap kits and can sometimes cause issues in the vertical section — still there. I booted the board where I could get to the bottom and tested the voltages at the vertical IC. They were all in spec. However, an ECG 1797 10 pin was used in place of what should have been an LA7833 7 pin vertical IC. It worked, BUT was enough spec difference that it was causing the issue. I removed the ECG1797 and replaced with the proper 7 pin LA7833 and it was perfect.
Once we got MK2 all good though, I noticed the sound board wasn’t working. Sound boards on Mortal Kombats have started to have a decent amount of issues with original caps in the past few years. So, MK2 sound board came back with me to iron the last bit of that out. A k4600 in a Pac Man that is playing blind will be replaced with a Vision Pro CGA direct in LCD, and a Defender cocktail machine will be wrapped up. A new power supply brought it mostly back to life, but it had original batteries on the board, sound issues and dried out old caps on the sound board, and sound ROM errors. That came back to get wrapped out as well. Stay tuned for Part #2 in the near future on this extensive repair!