I'm not sure if the problem with these four solenoids may be the consequence of a wire that had pulled loose from a molex near the 16-opto board, or completely unrelated. The pin sat for a long time after I started having some issues with balls kicking out from the left ball lock, and I forget what exactly it was doing at that point. But when I looked into it again recently, I found that a narrow, violet-yellow wire had pulled loose from a molex connector and was intermittently grounding against the bracket holding the 16-opto board to the playfield. I fixed that, and also replaced a bad opto receiver on the under left lock switch 1. The problem I am facing next is fuse F103 blows every time right after the pin is powered, and the diverters and top drop target aren't working. I've seen a couple other threads where there were issues with these solenoids/coils and that F103 fuse. Another issue, possibly related, is both cannons not finding home at power up test (I can move that to another thread later if it seems unrelated).

Taking a close look at the 8-driver board (is that aux board?) -- picture attached, it looks like it got quite hot at some point in its life on the right-side transistors (Q13-Q16) and had some work done. I believe those transistors are part of the circuit for the four problem coils/solenoids. The resistor beneath the transistor at the top looks especially dark. The condition of the board there is a bit of a concern, maybe I need to order a replacement? Not sure if I tested the transistors properly, but with the machine off I get high resistance when testing the center metal tab against the ground braid on each Q13-Q16. The four coils look okay, no obvious signs of meltdown. I'm not certain how to check those.

Any ideas on what to do next for troubleshooting? Thanks.

auxboard (resized).jpg

If I have a bad coil, would it possibly fry a replacement board? Should I consider replacing the coils as a precaution? I see that the coil on the lower diverter has been replaced previously since it's a Gottlieb coil -- hopefully it's compatible and didn't cause this problem. I agree for the nominal price of a replacement board there's not much point in trying to fix this one.

I saw another post where you'd mentioned that lavender green strip wire on the target up coil sometimes pulling loose and causing problems. On my system there is a single wire to the target up coil that runs to a small bundle of electrical tape where the two larger lavender-green wires and the thinner one are spliced together. I'll unwrap all that and double-check that it hasn't pulled loose under there and ensure they're soldered together and then enclose it all in some heat shrink instead of tape.