Blown R1A on Speedball large board

[DarthBubi]

Hi there,
after installing the Speedball upgrades on my Crack step by step. I first installed the first upgrade board with successful checks and tested it for a few days. Sound was great. After that, I went for the second board. Resistance and voltage checks were within the given tolerances. It worked for about five minutes, sound was muffled, which was strange changed gear for troubleshooting, but the resistor R1A blew up.
I'm a bit lost what the root cause could be. Wiring looked fine and the MOSFETs are properly isolated. The Crack itself ran fine for a few years. I've attached images of the build.

 

[Paul Birkeland]

It looks like there may be solder on the top side of the board bridging some connections on Q1A. Q2A is too close to the PC board and may have similar issues. Many leads on the bottom of that PC board are untrimmed, which also isn't OK.

Q1A and the resistor, at minimum, will need to be replaced. You can set your meter to beep for continuity, then check the TIP50 on the A side of the board to see if there's a short between any pairs of leads. If the TIP50 is shorted, then it will also need to be replaced.