Some parts from Pinball Life came today that let me do a repair of something that had taken me quite a while to realize it was even a problem. One of those things that maybe you know isn't right but it takes a long time to get to the point where you really see it for what it is - for it to really register in your brain.
After switching over to LED I had some problems with a few 555 lamps in a couple of locations. Lamps not always lighting and others full on when they're not supposed to be. Slowly realized that they were all the lamps in switch matrix column #2 - the top drop target lane and the two outlanes.
The matrix says column #2 is transistor Q64 and, sure enough, the DMM says Q64 is bad.
Purchased a handful of TIP42 transistors for this order, just in case. R&R of Q64 and - sweet success - everything works properly! Finally, something that fixes the first time and doesn't make me hunt for it.
I hope those LEDs didn't get it too bad though. I understand that the failed transistor was probably letting through a lot more voltage than what they were looking for.
While I had the MPU out I also replaced all three of the diagnostic LEDs. Somebody had broken the two closest to the battery holder - not sure how that happened but it probably had something to do with those damn batteries. The ones I used have a clear lens (red emitter) so I did all three to keep them looking the same.
Still have things to work on but today was a good repair day.