Update on the 24V 5A PSU

The capacitors (& filter coil) arrived and thus I was able to work on this again.
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)

FDPS-100N-R5 24V 5A power supply schematic

Heyo, this is a schematic I've drawn of this power supply while working to understand it - it might not be all correct, YMMV, no warranty, etc.

It's not a particularly good power supply - the L2 filter/coil is seriously under-rated (and/or insufficiently cooled, however you want to look at it) and this (plus the idle load resistor) cooked the output capacitors in mine - I'm waiting on new caps (& a different filter to experiment with) as i write this, so I don't know if mine has more trouble than that.

That said, it does seem very serviceable - simple one-sided PCB with through-hole components makes for super simple parts replacement, and the PCB even has a nice enough silkscreen with named components so you can find what I'm drawing in the schematic - if i bothered to name that particular component that is ... sorry.

This is the AC input all the way to the rectified mains caps. The most boring bit really. Not drawn: the 220/110V switch: it would in the 110V position connect one of the AC lines past the rectifier to the middle point of the caps.

This is the high-voltage side wiggly bits. I'll be honest and say that I don't (yet) really fully understand how this thing starts up (or some of the details of the controls).

This is how I've described the transformers in the PSU. W is named T2 on the PCB and Y is named T1. I don't really know why i decided to name their terminals Wx and Yx but what is done is done.

This is the first part of the low-voltage side logic - the bottom half of the TL494 chip and what it drives. I know my transistor orientation in the control drive section is funky, but sometimes you make some happy accidents.

This is the top half of the TL494-related circuitry - mostly what it senses.

Finally, the DC output section (and the feedback adjustment stuff).