Additional irony on top of that: I just had need to go to the Hypex site because my unlucky friend got an Edcor prototype with the high and low voltage windings misidentified. Besides the immediate effect of blowing up one of the low voltage caps on his (custom) preamp board, he may have blown up other things on that board (repairable) or his Hypex module (if it's the modulator board, unrepairable; it it's other parts on the module, repairable but will take some substantial trouble). Of course he needs the thing immediately.
EDIT: Looking at the board on the Hypex website it does look like at least Don was correct, that only the high voltage connects to the amp module. That means that his problem is on the preamp board and susceptible of repair. That's a relief. I guess the reason he used the low voltage of +/- 12V is that it (or its AC anyway) was provided from the initially-purchased Hypex power transformer.
EDIT II: Good news. The Hypex module and the preamp were both fine. The Hypex amp #2 was merely shutting down due to Don not appreciating how high the voltage on the lightly loaded unregulated power supply would get, and sizing the Edcor transformer inappropriately. The Hypex was protecting itself, and evidently amp #1 had a slightly different threshold and managed to function.
Reducing the line voltage a bit brought everything to life. Variac anyone? :razz:
