ASUS PSU high voltage on electolytic capacitor?

[rks96]

Hi! ASUS PSU block ADP-90CD DB blow up and shorted. The main breaker also popped! When I peeled open the casing, I found out that the electrolytic capacitor had blown. Ordered a cheap replacement in hopes of having a spare PSU block after a simple fix. When I replaced the electrolytic capacitor and tested the unit, everything worked as it should.

Electrolytic caps are usually one of the components that go first in electronics, so I wasn’t surprised that the capacitor failed. Out of curiosity more than anything, I measured the voltage on the capacitor ,and it was nearly 500V, but, the capacitor is rated 450V!?!? This can’t be normal!! After searching online for PSU model, I found this post in Russian with exactly the same damage except in this case, the PSU failed in open circuit mode!
https://easywork.com.ua/remont-bloka-pitaniya-asus-adp-90cd-db-2.html
As far as I can understand, while using Google translate and my minimal understanding of electronics, the author of this post simply replaced the capacitor same as me and called it done? In this case, there is 464V on the capacitor. So, my question is … is it ok to call PSU fixed and use it as it is?

The author of the post also links to a Russian forum where there is more discussion about this exact problem and it looks like power correction could be the cause of this problem.

[wraper]

Most likely some resistor in PFC output voltage feedback loop failed open or its resistance drifted.

[wraper]

Schematic over the link is not a schematic of this PSU but typical circuit taken from PWM controller datasheet. It has nothing to do with PFC. Voltage after PFC usually is about 400V and for sure it must not exceed rated voltage of the capacitor. Voltage in power supplies witout PFC should be below 350V.

[MathWizard]

Normally if the controller chip is working, and everything to it, it should slow down or shut down if the voltage gets that high. On ATX PSU's I've worked on, it's usually sensed through a few high value resistors, and a small 1, which divide ~340V down to ~ 1V, for the controller chip. If it gets too high, most chips should just shut down/reset.