I replaced the 4.7µF caps, and the 100µF TL494 power supply cap just as a precaution and bumped the output caps to 680µF low ESR (35V still) ones - a random one tested as 0.05ohm in my cheap tester.
The mains caps tested good and i couldnt find any good replacements in the shop I was ordering from so i left them alone - I also tested the 1µF main-side-swingy-cap, that was good too.
I was going to just skip (just remove it and put a big jumper wire under the PCB) the filter coil, but found an 8A 5.6µH filter in the shop, so just so i dont feel so bad about it I installed that instead. I'm sure it has way less filtering effect than the original one, but atleast it is rated high enough amps and is some sort of a filter instead of nothing (also the output caps are higher µF now so maybe that helps a bit too). And also I moved the load resistor further away from the caps so it's not purposefully cooking them.
This is what the output section looks like after these mods:
With these upgrades the power supply (to all the tests i can do right now) seems to operate correctly - can run my load (smallish really, 1 to 2A ish) just fine and doesn't buzz like it used to even on idle.
I also installed a slow fan on it for a longer & cooler life of everything.
(And yeah I know it's wild, this post makes 2020 the first year with more than a single post. OTOH i skipped 2019 so it balances out, don't worry... yet atleast :P)
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