386SX wrote on 2024-03-15, 16:43:

Which is the status of modern "new" retro oriented -5V compatible PSUs for AT mainboards? Are there any new ones I'd use on a AT or ATX late 90 system on the market built in modern times specifically for them?

Just get yourself
1 of these: https://uk.farnell.com/stmicroelectronics/l79 … 141?ost=1087141
and
2 of these: https://uk.farnell.com/panasonic/eeufc1v330b/ … dial/dp/3253996
and you can make and add a -5V pin (white) [pin+wire from a dead PSU], directly to any PSU's ATX connector that is missing it.
The converter is outputing -5V (white) from -12V (blue) and ground (black). So it would be preferable to use it with a PSU that outputs 0.5A (not 0.3A), on the -12V.

I made mine on a little PCB, and a bit more complicated.. but you don't have to.. and you don't need a PCB.
I later isolated mine by putting it in a little plastic case from inside a Kinder chocolate egg.

Alternatively, you can incorporate the convertor into one of these ATX extensions, or ATX-to-AT adapters, that (both) already have the white wire... Which would make things much easier to build, AND detachable! 😀 (just DON'T ever connect them to a PSU that already has the -5V white wire)

(EDITED) TL;DR : This project's electronics are based on the Voltage Blaster project, but DOES NOT connect to an ISA slot, but to the ATX connector.
You can also use these Voltage Blaster pictures to understand how to connect everything:

I hope it's clear

I use the voltage blaster mini https://www.youtube.com/watch?v=b2XOo_8uzvw

But this is the best solution I’ve seen so far. See at 5:30. -5 is injected in at the ATX adapter.

https://youtu.be/iGlIgqNpK50?si=asg80lmBwxI7Dh4b

Thanks both. I think the solution before the AT connector seems the better one and look better to insert the voltage at the PSU level instead of the bus rail.
As modern PSU voltages/balances to use, any problem using them for such different usage? Is it safe in the long run if eventually the converter would fail?

zuldan wrote on 2024-03-15, 21:34:

But this is the best solution I’ve seen so far. See at 5:30. -5 is injected in at the ATX adapter.

https://youtu.be/iGlIgqNpK50?si=asg80lmBwxI7Dh4b

81D4629F-06AC-46EB-886F-635D637D3382.jpeg

386SX wrote on 2024-03-16, 07:21:

Thanks both. I think the solution before the AT connector seems the better one and look better to insert the voltage at the PSU level instead of the bus rail.
As modern PSU voltages/balances to use, any problem using them for such different usage? Is it safe in the long run if eventually the converter would fail?

The solution I posted IS before the AT connector of the motherboard... 🙄
Also requiring the minimal amount of components to create, while maintaining compatibility with any case and motherboard
(a 90 degree ATX connector may present problems with many motherboards. That's why I recommended an ATX extension, or ATX-to-AT adapter, for anyone who wants to make it detachable from the PSU.).

The components I linked to, are of really good quality... (most likely far better than in the average PSU )
But if the converter IC should fail, it should remain open, and basically just not output -5V anymore, while not consuming anything.
If by some mishap, it fails and shorts the -12V rail to Ground; than that's up to the PSU to handle. A PSU with good short-circuit protection, would simply not turn on anymore until the short is removed. Except for in the case of the absolute most shittiest PSU, the PC components should very VERY most likely remain unharmed even if the convertor fails.

B24Fox wrote on 2024-03-16, 19:42:

The solution I posted IS before the AT connector of the motherboard... :rolling_eyes: Also requiring the minimal amount of comp […]
Show full quote

zuldan wrote on 2024-03-15, 21:34:

But this is the best solution I’ve seen so far. See at 5:30. -5 is injected in at the ATX adapter.

https://youtu.be/iGlIgqNpK50?si=asg80lmBwxI7Dh4b

81D4629F-06AC-46EB-886F-635D637D3382.jpeg

386SX wrote on 2024-03-16, 07:21:

Thanks both. I think the solution before the AT connector seems the better one and look better to insert the voltage at the PSU level instead of the bus rail.
As modern PSU voltages/balances to use, any problem using them for such different usage? Is it safe in the long run if eventually the converter would fail?

The solution I posted IS before the AT connector of the motherboard... 🙄
Also requiring the minimal amount of components to create, while maintaining compatibility with any case and motherboard
(a 90 degree ATX connector may present problems with many motherboards. That's why I recommended an ATX extension, or ATX-to-AT adapter, for anyone who wants to make it detachable from the PSU.).

The components I linked to, are of really good quality... (most likely far better than in the average PSU )
But if the converter IC should fail, it should remain open, and basically just not output -5V anymore, while not consuming anything.
If by some mishap, it fails and shorts the -12V rail to Ground; than that's up to the PSU to handle. A PSU with good short-circuit protection, would simply not turn on anymore until the short is removed. Except for in the case of the absolute most shittiest PSU, the PC components should very VERY most likely remain unharmed even if the convertor fails.

Yes I meant that the solution in the ATX adapter seems the best compared to the ISA PCB solution. I am sure my 386 board is unstable without the -5v so having it at the AT connector is indeed what I wish. I will go for it, any modern low watts PSU I can use along with this that has been tested having also a stable +5v too?

Honestly, for the kind of current a 386 system will draw, any brand-name PSU will do.

Minutemanqvs wrote on 2024-03-17, 09:42:

Honestly, for the kind of current a 386 system will draw, any brand-name PSU will do.

Thanks, of course the current will be low but I wonder how much stable the 5V rail would be and filtered from peaks even higher than the expected.

386SX wrote on 2024-03-17, 07:00:

any modern low watts PSU I can use along with this that has been tested having also a stable +5v too?

The cheapest decent PSUs, seem to be the Segotep ATX-500WH that I reviewed here, and the LC Power LC6560GP3 v2.3 80+ Silver.
Though nobody actually measured their output stability with an Oscilloscope; they DID seem to pass the test of time, with some users here.

But I really recommend giving this entire thread a quick read.