Published Friday, July 27 2012

Oh my God! I know what I did wrong with the power supply. Good heavens!

DEC used GPSA05 (NPN) and GPSA55 (PNP) transistors. I replaced two that were shorted out with MPSA05 and MPSA55’s. They have completely identical specifications.

But guess what? THEY USE REVERSED PINS. Pin 1 is the emitter on the MPSA05/55’s. It’s the collector on the GPSA05/55’s.

Lesson learned: ALWAYS CHECK THE TRANSISTOR ORIENTATION. Especially when you’re 110% sure the parts are identical.


I will report back after I have fixed my mistake.