My right kicker coil on my System 11 Road Kings locks on when I enter test mode, as well as when the game is started or any time power gets to the coil.

I got this Road Kings in 2015 that had been left in a bowling alley that closed after a flood in 1991. I've been working on it off and on since then. I refurbed it and got it working well and cleaned up except for this one problem. I Replaced the Q71 transistor. Problem recurred. Sent the board out for repair, came back with a clean bill of health, and problem recurred. Tried replacing Q71 again, still locks on. I've replaced the coil. I've traced both the power and return wire, can't find any issues.

Nobody makes an early System 11 replacement board and mine looks better than the "tested" ones I see for sale at shows.

I'm proud of my refurb efforts and the game is actually pretty fun to play, but this coil issue is ruining my accomplishment! I'm at the point now where I'm ready to remove the coil and just play with a dead bumper unless you guys have any ideas.

I think so. Its a small three prong thing. I think I replaced that a while ago. Should I try again? How can I test it? I've tried following the directions on the System 11 repair guide, but my DMM doesn't have a "tone" setting for Ohms, and my DMM never reads zero for ohms like the guide says for a bad transistor. I'm an electricity noob, and an totally confused by the DMMs.

I have checked the switch contacts, and they are not triggering. No solder blobs noted on the switches. How do I test the switch capacitor? Sorry for being so clueless on electricity. That's the only thing I haven't checked. I have been getting the .4 to .6 readings on the Q71. Will check the pre-drivers. Thanks!

Thanks DA, will try your suggestions.

Blackbeard, can't remember at this time. Somewhere in the nidwest I think. Got the link from pinside here. It was maybe 4 years ago. I left the hobby for a few years , and just coming back. Went back to my other love, woodworking, where annoying electrical problems don't exist. Now trying once again to get some project machines up and running.

DA, I did as you suggested, disconnecting IJ18 and the lock on persisted. It did not lock when I turned the power on, but did both on starting a game and testing. So it is upstream from the transistors. How do I fix ir on the logic side? Do I replace U25?

Thanks for your patience.

Thanks DA. Will try to get on it this weekend.