A while back I noticed my Klipsch ProMedia 2.1 speakers had a failure. One channel didn't work. The sub and other channel seemed unaffected. I swapped speakers to see if that resolved anything and checked connections. None of this resolved it. So I opened up the enclosure and the damage was obvious. The familiar smell of expensive and elusive smoke. It seems one of the HF amp boards had blown components. A resistor of unknown resistance and the left MOSFET were blown in half. After doing some research, I determined the value of the resistor and that the MOSFET was a TIP41C. I ordered electrolytic capacitors for all on the board, the TIP41C, TIP42C and a capacitor on the underside of the board that looked a little crusty. My suspicion for the cause of the failure was solastic (sp?) going conductive. This HF amp board had a good coating that had run off from another component, but the other unaffected HF board had none. I scraped all of the run off solastic off, replaced the resistor, electrolytic capacitors and pair of TIP41/42C chips. I reassembled it all, powered it on and in a flash and poof, the smoke came out of this set of components, frying the TIP42C and the resistor. This failure is similar, but of the opposite chip, as to what I found initially. So, as I have run out of my depth in electronic repair, I thought I would beg help here on what could be the failure point.
The schematic linked is the one I used to guide my repair, and looks correct so far. I am assuming the resistor frys just a bit too late to save the chips, but any ideas on what's gone wrong in the circuit? My initial thought was something got grounded that shouldn't have and cooked a component, but that doesn't appear to be the case, or at least not in the method I thought. I have replacement parts, but, I don't was to blindly try again. R17 has blown both times, Q9 was initially blown in half, and Q10 did it this time.
http://christopherbradshaw.net/The_Project_Bin/Klipsch%20ProMedia%202.1%20HF%20Amplifier%20Schematic.gifAdam