I would put it that the stress caused by repeated intermittent dc surges can be cumulative. It's not that energy is getting stored, just that repeated stress eventually causes some component or components to reach a breaking point.
Just as a point of information, resistors don't store energy. Capacitors and inductors (coils) do. And if the units were turned off that energy would pretty much dissipate within a few minutes.
It does sound like intermittent dc surges from the preamp are the cause, very conceivably due to a bad capacitor. If they are brief and/or intermittent chances are your voltmeter wouldn't detect them.
Regards,
-- Al
Just as a point of information, resistors don't store energy. Capacitors and inductors (coils) do. And if the units were turned off that energy would pretty much dissipate within a few minutes.
It does sound like intermittent dc surges from the preamp are the cause, very conceivably due to a bad capacitor. If they are brief and/or intermittent chances are your voltmeter wouldn't detect them.
Regards,
-- Al