I paid $40 for one of these: https://www.amazon.com/dp/B091DS1MM6 and am very happy with how it worked out for my 486 DX2/50. Very quiet, all the cables I need, and no issues with power delivery.

That seems to be no longer available. I opted now for a Gigabyte 450W one, because it has lots of molex connectors and seems reasonably prices. I will also try and check the old PSU, might make for a nice repair. If I can figure out if and which regulator is bad.

I swear by (new) Seasonic PSUs for contemporary machines as well as my holy retro treasures*. They seem to be the most reliable brand out there. All of them, even the entry level models, have cable management which means I ended up with a collection of Molex cables over the years that I can use for my older machines.

Regarding Gigabyte PSUs... They don't have the best track record of reliability.

* The Pentium 3 era is a problem because of the 5V line, but I found an older used Seasonic model for them, caps seem to be of high quality.

Seasonics are overall pretty good and worth the investment. However, they also have bottom of the barrel editions. I'd personally pass on a $40 PSU. When you see a PSU you think of using/purchasing, you can use this reference to see who made them and get an idea of quality:

https://www.tomshardware.com/reviews/psu-manu … oem,2729-4.html

Another PSU discussion from a while back: PSU showcase: The worst of the bad

Keep in mind that 550W PSU, bronze or not, will most likely have poor efficiency at loads that a 486 systems generate. And the regulation might be poor as well. People usually greatly overestimate just how much current is needed at 5V rail so unless the PSU is going to be shared between various systems, including P2 and P3 ones, you will only need up to some 5A for a 486DX. Let's say 8A if DX4+ will be installed, and that is on the safe side too.

Well, unless you need several old mechanical HDDs. Then I guess it'd be prudent to have more available power for the spin-up. But each HDD adds about 1A max, worst case, most of the load for these will be on 12V rail which is otherwise unused in modern build (except well below 100mA for some VGA cards). And maybe floppies, but this too is mostly 12V load.

Yes, I have the ATX2AT so I can tell you I only need about 3A maybe 4A tops for my whole system. Problem is that there are not small ATX PSUs that I can fit in the tower. I will have a look at Seasonic. There were none with small Wattage available here when I checked, but I will look harder.

The seasonic eco plus 400 looks fine, but I can find it nowhere to buy here in Germany. Would have enough Wattage for my 486.