Nearly any old atx psu that has the correct ventilation characteristics for your application as you say should do the trick for that build. Even if you have to use a 24 pin to 20 pin adapter. Super socket 7 builds don’t use that much power.

That voodoo might take a little bit of power though. But still probably well within the envelope of any old atx psu you may have laying around.

Some isa sound cards want -5v which later psus dropped support for btw. So look for that -5v wire if that is a voltage you need for your specific isa sound card.

Btw, you are asking for trouble with that sata adapter.

Try a stand alone bootable sata card. I like the promise sata II tx4 myself

Autumn Able wrote on 2022-10-08, 09:50:

However, most modern PSUs have a large fan port in the top of them which gets almost entirely covered by the top cover of the AT desktop case. It maybe gets 5mm of space between the fan and the case lid, which I doubt will be enough for good ventilation. So I'm wondering what I should go for that doesn't have this issue?

Most photos on the internet present psu's with the bottom up showing the fan, not the top. When you install one matching the a-symmetrically placed screwholes in the backplate it will usually be allright.
https://seasonic.com/how-to-position-your-power-supply#

Those are mainly for ATX towers. This case has the PSU aligned horizontally with the case itself in a horizontal position. The bottom portion is also mostly blocked off due to a hard drive mounting bracket under the PSU. One I'll likely use in case I ever find a better front plate that allows me to install more external drives. The case could hold 3x 5.25 external drives and 2x 3.5 external drives, but the front plate only has spots for 1x 3.5 and 2x 5.25.

That does not look very positive in terms of airflow. If you are going for a high-end build with components that produce above average temperatures you could, or maybe should, consider using another case.

If you're not afraid to spend a bit more I think the Seasonic SSP-650RS may fit the bill:
-80mm fan at the back
-35A @+5V / 20A @+3.3V (200W combined)
-as far as I can tell 5V&+3.3V are generated from +12V so no balancing issues
-still has regular 5.25" drive and FDD plugs
-20+4 ATX plug (judging from pics)
-grey case
-all relevant protection features
-80+ Gold (probably not that relevant)
Seems to be a solid retro PSU overall. Only obvious shortcoming is the missing -5V rail but as we know there are ways to still get -5V.

I have to agree with PARKE though: Make sure your case has sufficient airflow. The PSU won't spin its fan as fast as a contemporary PSU normally would so it won't pull as much air through. It's a very nice case but since it is probably designed around 386/486 hardware it won't be that great on ventilation.
Maybe get one or two of those radial slot fans that suck air out of the case?

Also the case has a latching power switch that you'd have to swap for a momentary switch to use an ATX PSU in this case.

Doornkaat wrote on 2022-10-09, 12:18:

If you're not afraid to spend a bit more I think the Seasonic SSP-650RS may fit the bill: -80mm fan at the back -35A @+5V / 20A […]
Show full quote

If you're not afraid to spend a bit more I think the Seasonic SSP-650RS may fit the bill:
-80mm fan at the back
-35A @+5V / 20A @+3.3V (200W combined)
-as far as I can tell 5V&+3.3V are generated from +12V so no balancing issues
-still has regular 5.25" drive and FDD plugs
-grey case
-all relevant protection features
-80+ Gold (probably bot that relevant)
Seems to be a solid retro PSU overall. Only obvious shortcoming is the missing -5V rail but as we know there are ways to still get -5V.

I have to agree with PARKE though: Make sure your case has sufficient airflow. The PSU won't spin its fan as fast as a contemporary PSU normally would so it won't pull as much air through. Also the case has likely been designed with cooler running hardware in mind.
Maybe get one or two of those radial slot fans that suck air out of the case?

Also the case has a latching power switch that you'd have to swap for a momentary switch to use an ATX PSU in this case.

Already have the replacement momentary switch. Came in a pack of ten, so I'll have plenty more if I need them in the future. As far as ventilation goes I have a 80mm Noctua fan for the front intake, but if I have the free PCI slots I just might go for one of those slot fans to be extra sure. I did find a rather good PSU though: A Thermaltake TR2-430. It has 80mm fans at front and the back, and was made well after the capacitor plague. It also has a proper 20-pin motherboard power connector, and plenty of molex and SATA power. I'll be using the SATA power with the Noctua fan using their own SATA power to 4-pin fan adapter. As far as other hardware goes, it'll be pretty basic: A YMF719E sound card, a USB 2.0 PCI card (NEC chip, which will also connect to a MMC reader that's built into the 3.5 floppy drive), and maybe a PCI ethernet or WiFi card in the future.

I can't say anything about that Thermaltake PSU. I understand choosing a vintage part over a 100$+ new PSU though. Keep in mind though capacitors age regardless of wether they're from the capacitor plague era or not.

If the case has decent air intake with an 80mm fan thermals should be fine for a Super 7 system.
Have fun with your project!😃👍

K6-2@450 and Voodoo 3 2000 was where I first ran into thermal problems with desktop cases back in 2000, had a front 80mm intake and rear 60mm plus PSU and I still had to run with the cover off if I wanted to game for more than half an hour. Found a drivebay 3x35mm fan blower a while later, and leaving the slot cover off next to the voodoo (component side) let that leak heat well enough... still didn't like summer though.