MasterBlaster84 said:
saxonman said:
I asumed belts were a given lol
Just about all 30 year old belts are shot or very close to it but even if many caps aren't in good shape they still work well enough to use.
Any part that degrades enough to require service is considered a failure, even if what it requires is as simple cleaning because 30 years ago, nobody would take their boombox apart and spray deoxit so it would go to the service center.
(1) Failures rates are typically highest in mechanical parts such as belts, switches, and pots, pcb traces and connections. Trimpots are especially prone to total failure (burnout from being undersized?)
(2) I've had lots of capacitors go bad to where one channel was dead. Don: It's true that when they degrade, performance suffers but still works. But total failure (shorted to ground, open) is not uncommon at all.
(3) Amplifier output modules
(4) power resistors
(5) top side traces on early boards, did not use foil traces. Instead, the traces were painted with a conductive material that degrades over time and fail. This is very common and whenever I see a dual sided board with top traces painted on -- I immediately suspect those traces, especially if one channel is dead for no good reason. The TRK-8080 and RX-7000 and S90 are examples (models) that use these types of boards.
(6) pcb "painted-on" resistors and other components.
(7) zener diodes
(8) degraded or failed transistors.
I've found signal resistors to be fairly reliable and given how many are used per device, they rarely fail if sized correctly to begin with so they are not usually my first suspect to interrogate.
