So I'm having a problem repairing a williams Rottendog board that came out of an Addams Family pin. The board was brand new and installed 4 or 5 months ago without any problems until now. Q82 drives the chair kickout coil and it's a 13n10L mosfet transistor, it blew for no apparent reason (I checked the coil, it was fine and then replaced it just to make sure). I replaced the transistor and the game ran fine for a week and then blew again (on location running for 80 hrs a week or so). So I replaced the transistor again and it was locked on as soon as I installed the board and powered up the game. Replaced it again to make sure I didn't mess it up and it's still locked on. So I threw a different williams board into the machine and it works just fine and has been working for a month now without any problems.

So it sat for a while and now I'm back to trying to fix this Rottendog board. The first thing I tried was installing an IRL540N instead of the 13n10L, which should be a bit stouter then the 13n. I also installed a new diode on the board even though I cut the leg and it tested fine. Locked on immediately. I checked the transistor after I installed it into the game and after it locked on and the transistor checks out okay with the meter. Just an FYI, I put as little heat into the transistor when installing them and put an alligator clip on the legs to keep the heat down as well and I use a static wrist strap to protect for ESD. I know mosfets can be sensitive to heat and static discharge.

So now I'm 99% sure the transistors are fine and something else must be causing the issue. Could U5 (I think U5 controls Q82, but I can't seem to find a Rottendog wiring diagram for this board)cause the transistor to turn on? Maybe the blown transistor damaged the chip? Could it be something further upstream that was damaged from the blown transistor causing the problem? Am I doing something wrong when I'm installing the transistors?

This has been bugging me for a while and I'd definitely like to get it figured out. Any help on what to replace or check next would be much appreciated. Thanks in advance.2016-08-23 20.19.56 (resized).jpg

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That is probably what it will come down to if it's something easy that I can't fix myself. Good to hear he stands behind his products!

Bump. Anyone else have any ideas on this?

Yeah, I replaced the diode already.