There are troubleshooting steps on pinwiki. If that doesn't help there are good techs who can repair your boards for less than the cost of a new one. Resoldering all the pins is way too much until you know what the issue is.

It does sound like a power issue though. Pinwiki will have info on testing the power supply. You'll want to test before and after an incident.

Ben, by any chance is your game using an extension cord to get to the outlet? If so, try moving your game closer to the outlet so you don't have to use one and see if that helps first. Then, if the problem is still there, troubleshoot the game.

Steve

See "3c. When thing don't work: Game Resets/Boot-Up Problems, and Immediate Blowing Fuses."
http://techniek.flipperwinkel.nl/wms11/index2.htm#reset

Many times on System 11 games this is a bad diode. Is it happening when the ball is at a certain spot on the playfield? Can you narrow it down to a single target? Could be a bad diode. These cost like 20 cents you can replace them pretty indiscriminately if you think you know where the issue is.

Could also be a slam tilt switch but I don't think that causes a total reboot, just a reset.

Also try turning off your air conditioner or moving to a different circuit. You may just have low power.

Bummer, I had the same issue show up on one of my route games years ago, it took me a little time to figure out what had happened because the symptoms were random. Turns out that the manager of the bar had moved my game and used a cheap extension cord to connect it back up. The cord was choking the game out but I didn't see the cord initially when I went in to fix it. So, when ever I hear of resets, I always think of cords first.

Steve

Here's the Game Resets section on pinwiki http://pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#Game_resets

You're going to start with reseating all your connectors. While doing this look for anything burnt. If this doesn't fix it then make sure all your chips are firmly seated by pressing down on them. If any of them go back in then that might of been your problem.

After this is gets into electronics testing. Search for Pinbot game reset or system 11 game reset and see if you can isolate it to the power supply or mpu.

Good luck