Had that happen once, but it was the power company’s AC coming in to the house.
Left the stereo on, was outside, playing with and walking the dog....came back in and the power was cycling, on and off...at about the rate of just over 1 on/off cycles a second.
Right about at the correct rate to blow up a power amplifier, as best as possible.
In this case, the amplifier was of the kind with no protection circuitry of any kind, other than a fuse and power switch. The best sounding kind of added protections, which is: NONE. (’Best’ in audio quality means: Go big or stay home)
It also had three hundred thousand microfarads of capacitance in the power supply, at +/- 90VDC, or 0.3F (farad)/90VDC. This amp would run for 30 seconds after it was shut down. Full DC capacity, zero problems with being like a DC power supply, instead of being an amplifier for audio. (hitting the power switch will not save your speakers, foolish puny man!)
The amp had blown a main capacitor, but just...kept on going, zero in the way of failsafes (just the way I like it), but also blew a set of prototype speakers, where the drivers where no longer available, anywhere.
Not my best day, but far from the worst. It was just audio, not life nor..the records.
The AC continued to cycle like that for nearly an hour.
I still like my amplifiers to be that way. The gain in sound quality from the lack of the extra circuitry, relays, etc, is worth that much to me. I’d pay many thousands for it, like others do in various ways. In this case, I paid in damaged goods, in the given luck of the draw.
Art was burned by chance, and not much else.
We don’t truly know that, the capacitor might have been run too close to it’s voltage spec, but in well designed gear, it’s unlikely to be a problem even there. (re fire)
Conservative design rules the roost in the west, as, in the west...we’ve learned all the fire lessons we ever want to see or deal with, over the past 100+ years of electricity in homes. We've built up a system of specifications in parts and design and use of parts.. so that the correct amount of overhead remains in any given part and design application. All our build and design professionals are trained in this way. (that would be a 'design technician/technologist'. We used to have these as actual degrees available in schooling... engineers don't get much on this all important point in electronics education/build)
China? eBay? Not so much. Very very not so much.
All that DIY stuff out of china is not done by the level of professionalism and knowledge that is required to make sure that things are safe, stable, and long lived and don’t start fires in your home. The parts inside don’t have enough quality and overhead built in, the kind that comes from quality base materials inside the given part itself, nor the designer and builder of the part having the background for it in lore learned.
20 years from now, it will be better, but right now, it is still the wild west in circuitry and parts, out there in eBay DIY cheapo land.
Few in the west, as casual buyers, have any chance to understand such, as they’ve been under the protective umbrella of professionalism in electronics --- for their entire lives. So they buy this eBay kinda stuff, with no idea whatsoever of what they’ve allowed into their homes. A literal Sht-ton of dangerous and bad design, build and part decisions, in quite a few of them. And if that stuff burns your house down, and the insurance company figures it out, you’re out of luck. That stuff generally has zero regulatory or inspection approvals of any kind.
