Klipsch KSW-300 Amp Repair


I was at Goodwill and found a Klipsch KSW-300 subwoofer for $60. I've owned subs with six inch woofers before but had always been curious what a fifteen inch woofer can do. I took the thing home knowing it needed repair. I just had to find out how it sounded. At nearly eighty pounds this is a beast of a box. Although it played bass there was a pronounced hum coming out with and without inputs. It was audible enough to be annoying and can be heard across the room. Running an electric motor on the same outlet made the woofer rattle. After the subwoofer had warmed up for a few minutes, turning it off and back on would fail. One of the relays buzzes and the subwoofer never completely turns on. When working there should be two relay clicks. If I let it cool down for a few minutes then the subwoofer will turn on.

I took the amp out. I spotted four capacitors adjacent to two voltage regulators. The branding was Soundia, which I've never heard of. They were only rated 85°C despite their proximity to the hot regulators. Sure enough, after removing the capacitors all four were toast. ESR measuring in the kilo-ohm range and capacitance at 50%. In fact, the leg on one broke off probably from vibration or corroded by the aging electrolyte. This thing is over ten years old.