My initial Crack build has been working great for a few weeks now. I felt I'd had enough of a sample to proceed with the Speedball upgrade. I had done the PCB boards a couple weeks ago, so it was an easy install. I was doing my final checks on the bigger board, with the negative probe on 12U.
I had checked OB, and it was showing 106V. Wasn't quite sure that was okay, so I glanced over to the manual, which said +/-10% is typical. So I continued and put the clip probe on OA, while glancing to check what the manual said about the OA voltage. Apparently, my unsteady hand (unsupported, because I'm using one arm only, and keeping a safe distance from the amp) made the clip probe slip off the solder point of OA, and the probe touched some(?) of the leg(s) of the TIP-50 transistor at Q2A. I'm pretty sure I read a warning about these transistors somewhere, and I thought I was being careful, but clearly not enough.
There was a quiet "pop", and the 2 red LEDs on that side no longer light up. The LEDs on the "B" side are still lit. I immediately powered off, in case it was going to cause further damage. I don't know whether I shorted the transistor legs, or if I just hit a single leg and ran some current through it straight to 12U (I didn't analyze the schematic so I don't know what effect that would have). I just know when I felt the heatsinks, the A side (blown side) was significantly warmer than the B side (good side).
I'm guessing this is clearly a dead TIP-50 transistor, but could this have also damaged other components (LEDs, tubes, etc.)? What's the best way to check? I was able to cleanly de-solder the 3K resistors, so I could probably revert the big board, and put those back in, I guess...
Thanks for any insight or suggestions.
[Edit 10/24/22] Thanks to Paul, Doc, and Eileen, I received my replacement parts in 3 days, and have a fully functional Crack + Speedball working on my desk! Appreciate all of you guys!