Newbie here. Got EBD recently that was in decent shape. Needed some TLC so replaced all drop targets, rubbers and converted to LED. A few solenoids were weak so also did pop bumper rebuild along with a flipper. I made rookie mistake and wired one bumper coil backwards!!! Replaced diode and cap on driver board and all was well....or so I thought. Somewhere along the line the out hole and left out lane switches quit registering. Looked at schematic and realized that those switches are on same line as bottom bumper (the one I mucked up). Did switch test and bumper switch did register....and crazily the other two switches started working!!! But oddly the game started and had 30 credits which never happened before. Played 3 full games then it blew 5amp fuse. Replaced fuse and everything worked but the out hole and left out lane switches are back non registering. When that game started it had 20 credits. Walked away for a day and now game starts with zero credits like before. Same switches not working. Going to check all of my connections to find what’s causes short. Thought I was really careful after my goof but who knows. I have NVRAM chip coming for U8 replacement so I can get rid of battery. No corrosion noticed but got advice I should do that anyway which makes sense. I know the switches are good since they worked for 15 minutes.

Did I fry my MPU board?

Kinda sounds like it. Will see what happens after NVRAM install. I don’t want to install $200 MPU board and fry that one too.