I have a CBW that at first would not load multi-ball (2 ball) correctly. It would hold first ball ok in habit trail, but would not load another ball to shooter lane. I ran through the self test and found the trough switch was out of adjustment. Fixed that, game ran ok a few games then straight downhill. Now I can't get game to boot up at all. Beeps on powerup, 1 credit showing (not sure why "free play" not displayed though) LEDs flashing on 3 boards, sound ok (female says "One more for double"). I can get into first step of check mode , but game won't initiate any of the self tests (no flipper or start button recognition) Started checking boards (power supply, battery voltage on A1 board, etc) that's when I noticed a fried transistor on controller board (A3). Transistor fried is for the kicker solenoid, which come to think of it, I never heard work while I had game.
Question: could that fried transistor be causing EVERYTHING now going on? Or is it likely that was fried before and now I have multiple issues to fix?
Should the controller board just be replaced entirely due to damage? I can't imagine I could cleanly solder in a new transistor at Q30.

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Thank You both Yilb and Benhurr for your input on this! I ended up not learning from my years as an auto technician and was in the middle of fixing multiple possibilities at the same time...ending up in success...but not 100% sure which step truly fixed my issue. Probably a combination of a couple things. I think the possible ground issues could have caused a voltage spike/jump somewhere and then ultimately led to a blown "controlled lamps and switches" fuse. My A3 board is still running fine with that burn through and I think I'll leave it alone for now . My original problem, however is still there but MUCH more intermittent.

On a two ball multi-ball the game kicked an extra ball out I'd say 8 of 10 times. So I'll take it for now. If anyone's seen this intermittent issue with MB on this machine please give me some ideas.

Again, thanks Yilb and Benhurr for your help!

(Attached photos of my ground mods for reference)

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Benhurr: Good info. I'll check those values out next.

Brtlkat: HaHa...Yeah, I DID think of that after seeing a forum discussion a while back with the very same question on CBW. I have 3 balls loaded.