My son bought a dead Klipsch Subwoofer recently with SMPS. I did some simple testing and found that there was no positive supply reaching the amp board. There is a 7815 and 7915. I assumed the 7815 was dead and replaced it (although it looked ok) still no POS supply, so there is something gone on the SMPS board. Having Googled it seems that this is not uncommon. The board is made by BASH who make plate amps and some have bought one of these simply to replace the SMPS which is identical. However these of course have failed too.

It seems that the required voltages are +24v/-24v and 3.3v. I have thought about making a linear supply with appropriate transformer. What puzzles me is why there appears to be so much circuitry on the SMPS just to provide a couple of voltages.Are these for current limiting/short circuit protection or such like.

Would I be wasting my time? Trying to fix the SMPS would be beyond my capabilities as I have no test equipment.