[resolved] Crack + SB Woes. Left Channel dies after 5 minutes

[Blue]

So I pulled both TIP50 transistors away from their heat sinks to measure the voltages, the amp was on for no longer than 25 seconds.
B+: Starts at 185 volts, and then drops to 112 volts after a few seconds just like before.
What should I check for next?

[Paul Birkeland]

Honestly I would just replace the big PC board.  There's only so much debugging and rework that you can do on one of those PC boards before they are destroyed, and my guess is that you're getting close.

If the B+ drops like that with the TIP50 transistors not touching the heatsink, then you almost certainly have a shorted transistor on there. 

[Blue]

Yea, I’m going going to order an entire new big board.

I’ve already replaced the offending transistors twice, and I see no visible bridges between the transistor legs. I am not the best at soldering, but I really don’t see any bad joints.
Last week I checked for shorts in the transistors with my multimeter, but it showed it was fine.
Perhaps reinstalling the big board today caused a short.

However I’m not interested in damaging the rest of the components, and I’m slowly going crazy checking the same things over and over. I need to email [email protected] correct?

[Paul Birkeland]

Yes.

[Doc B.]

I just did a repair of a different kit, but with similar style of upgrade PC bards. The issue with that kit was that lots of the wires connecting the board to the circuit below had been nicked by the wire strippers used and the wire had fractured just inside the insulation where it wasn't visible. lt's worth checking the connecting wires themselves for continuity.

[Blue]

Thanks for your reply Doc.
I went ahead and checked for continuity in the wires, they seemed fine. However, I replaced the all the wires on the speeball big board anyway.
Still have the same problem.

I decided to check the 2N2222 Transistor and the LEDs on the board. The top side  of the big board were measuring properly.

The bottom side measured wrong though. The TIP50 measured correctly on the bottom side of the big board as before, but the
2N2222 transistor was measuring 1.025 volts from Emitter to Base when it should show over limit.  Also the the LED closest to the TIP50 transistor was not showing any reading at all.
It's the third time I had to replace the 2N2222 for similar reasons. However this is the first time that the LED failed to measure.

I'm still waiting on my delivery for the LEDs. If installing all new LEDs and transistors for the left channel don't work, I am going to purchase a new big board, as Paul said, it's probably better to do just that.
Thanks for your help everyone.