I've seen many cases over the years where the speaker relays internal contacts get dirty/oxidized etc. with the effect being low level noise/hash. cranking the volume up loud or power cycling will sometimes improve the connection for a short time. I've had this with several amps including an old KSA-150. As Magfan states, the relay(s) could also hard fail totally and not engage, or even "stick on". I've never seen these failure modes, but definitely not impossible... with the "stuck on" being the only obvious relay failure mode that could conceivable cause speaker damage.
I've also owned and re-built probably a dozen or so old Marantz 22XX and Heathkit AR-15XX series.
In my case I've never done any "cap-jobs" and have never had any failures. Some people swear by replacing all or as many as possible caps. Obviously if there were reports of a specific component failing, then no doubt.
I've also owned and re-built probably a dozen or so old Marantz 22XX and Heathkit AR-15XX series.
In my case I've never done any "cap-jobs" and have never had any failures. Some people swear by replacing all or as many as possible caps. Obviously if there were reports of a specific component failing, then no doubt.