My GFA-535 was problem-free for the 10+ years I relied on it. That said, the are Adcom amps that are notoriously failure-prone and so difficult to repair that technicians often have resort to aftermarket PCBs in order to bring them back to life and into spec -- so maybe we've just been lucky.
Adcom GFA 585 Part 1 (of 3) - First Look
Sorry but senior citizens disease did cause me neglect to mention the GFA 565's which were notorious for capacitor leakage.
To quote the Hoppe's Brain website, a serious Adcom guru,
"Nearly every GFA-565 ever made was affected by a bad batch of leaky capacitors that cause speaker-blowing DC offset to appear on the output. You can try to clean up the original board, but the DC offset issue often persists. The electrolyte actually soaks into the fiberglass, making it ever-so-slightly conductive. This affects the balance of the high-impedance circuitry around the input stage and DC servo. Amps that seem fixed can actually develop DC offset later on, as the electrolyte continues to spread through the fiberglass. It’s a frustrating problem to work on. A new board is the best solution. "
Adcom GFA-565 replacement circuit board.
hoppesbrain.com
In the long run I would just advise staying away from the 565's unless some very special desire forces you to keep one and want to upgrade it.
