Mattyice1994 wrote on 2020-08-06, 19:32:

Just to clarify, the sound almost sounds like something "decompressing" or "relieving" stress when I power it off. It is like a slight hiss coupled with a slight crackle. I imagine it as components releasing some sort of energy or stress in a way that shouldn't occur.

If I'm right that the hissing noise is caused by the PWM regulator chip not outputting any base drive to the transistors, I expect a constant hiss while the supply is powered on (and the primary stage has stable ~320V rectified mains [rectified+doubled in the US]), and a "relieving" sound when the charge on the big primary rubicon caps gets used up without being replenished from the mains. My experience with shorted supplies is that this relieving takes around half a second until the capacitors are depleted so much that the oscillation stops. It does not matter whether the cause for "no base drive" is a short circuit (that deprives the PWM regulator IC of its supply voltage), a broken PWM IC, or broken compents around the PWM IC, the kind of hiss is always the same.

TheMobRules wrote on 2020-08-06, 20:00:

So I'd say replacing them could be a first step in diagnosing the problem. You don't really need to replace the two big caps on the primary side, those are not known to fail very often except on catastrophic situations, besides they're Japanese Rubycons so you're good.

But be aware that the actual cause of the problem may be something else... usually it's easy to find replacements for every component in a PSU except for the transformers, but it may take more time troubleshooting than it's worth.

Two paragraphs of wisdom I could sign immediately!