retardware wrote on 2021-09-19, 12:34:
The zeners mentioned by @mkarcher are not designed to cut a surge like this.
Power was quadruple.
"Power was quadruple" would apply on resistive loads if the voltage is doubled. Zeners are even worse: They take virtually no power if the supply is OK, but take a lot of power (way more than four times virtually nothing) on 20% overvoltage. They get hot very fast, but they tend to fail safe: They become a short circuit if the core temperature exceeds 200°C.
Furthermore, a PC switch-mode supply is regulated. It will not output twice the voltage just because the input voltage is twice as high. The primary caps tend to fail within seconds (usually short, blowing the fuse) on 220V into a 110V unit, so the amount of energy available until catastrophic failure of the supply is limited. If the secondary side overvolts at all, it is possible that the zeners short out, kind of like a single-use crowbar circuit, but I doubt there is enough energy to melt the bond wires, which would allow overvoltage to leave the supply and damage the PC.
That's why I still have high hopes that no serious damage outside the supply was caused by the incident. Yet, of course, I wouldn't use the affected components in mission critical systems anymore.