[Refugee]

I have seen burned resistors caused by intermittent power.
If the power is interrupted briefly the grids of the valves act like a rectifier charging the coupling capacitors. This turns the valve hard on for a second or so and can burn anode resistors or even worse output transformers.
I was once asked to fix an AR88 that had the mains voltage selector all full up with charcoal. It had taken out the power feed filter resistors in the IF stages. The reported fault was intermittent heaters...