The thump is caused by a dc voltage offset (as you said dc accross the speaker). This offset is usually caused by the leakage of electrolytic capacitors accross the voltage reference diodes on the driver board. The capacitors are 25volts, 220mf, cost about 79 cents a piece (there are four of them to replace). However, when this happens, usually the reference diodes (6.9 volt temp compensated Zeners) or the bias control transistors (MPS-A63 and MPS-A13) also need replacement. Your technician is full of it, the power supply capacitors are very durable, and most likely are not the problem. By the way, the power supply capacitors, 120 volts, 36000mf, are very expensive, about $90 a piece, and are difficult to find. Your best solution might be to search on the web, e.g. Ebay, for Adcom repair services, which can cost you a couple of hundred bucks per amplifier.
Adcom GFA-565 Capacitor Replacement
I own two Adcom GFA-565 mono amps. One began to thump while in use, so I brought both to an authorized service center. Tech tells me that he is finding DC across speaker leads on both amps, and that oversize capacitors need replacing and that he thinks Adcom no longer makes them. I asked for alternatives, he said "they make great anchors". Is there a place I can obtain original or acceptable substitutes for the capacitors? THANKS!
- ...
- 11 posts total
- 11 posts total