Do you have another PSU? I know you said it's NOS but you never know, since you've tried multiple boards and also one that did work but then stopped...it's one of the common denominators.

sunkindly wrote on 2025-10-30, 16:12:

Do you have another PSU? I know you said it's NOS but you never know, since you've tried multiple boards and also one that did work but then stopped...it's one of the common denominators.

I only have a 15 years old 500W ATX PSU (the board supports it), I guess it's okay for testing, otherwise no, it has to be AT. 😁 All the AT PSUs that I have come with the PC cases, nothing separately.

For testing old boards I highly recommend getting some AT to ATX PSU adapters so you can use more modern power supplies:
https://www.ebay.com/itm/334858867116

I will admit that I haven't seen a lot of AT PSU failures, but considering the lack of safety and protection features on them and the lack of protections on boards from the time I prefer to use newer units.

Keep in mind that most adapters do not supply -5v from PSUs that do not have it, so you may want to get some voltage blasters at some point as well. Or make your own. 😀

Ozzuneoj wrote on 2025-10-30, 16:58:

For testing old boards I highly recommend getting some AT to ATX PSU adapters so you can use more modern power supplies:
https://www.ebay.com/itm/334858867116

This is interesting... However, the Chaintech mobo does support ATX natively, it has both AT and ATX connectors. I prefer AT only because of that brown "It's now safe to turn off your computer" text, and no momentary switch on the PC case. If a workaround for that exists, then I'd even use ATX as a last resort, because they usually don't have the monitor power outlet.

First I'll have to find out if the problem is in the PSU after all. It does deliver power. The MHz display lights up and the CPU fan runs (both get the juice from Molex). I can check the voltage as soon as I can, based on this: https://pinoutguide.com/Power/MotherboardPower_pinout.shtml

SGM wrote on 2025-10-30, 17:32:

Ozzuneoj wrote on 2025-10-30, 16:58:

For testing old boards I highly recommend getting some AT to ATX PSU adapters so you can use more modern power supplies:
https://www.ebay.com/itm/334858867116

This is interesting... However, the Chaintech mobo does support ATX natively, it has both AT and ATX connectors. I prefer AT only because of that brown "It's now safe to turn off your computer" text, and no momentary switch on the PC case. If a workaround for that exists, then I'd even use ATX as a last resort, because they usually don't have the monitor power outlet.

First I'll have to find out if the problem is in the PSU after all. It does deliver power. The MHz display lights up and the CPU fan runs (both get the juice from Molex). I can check the voltage as soon as I can, based on this: https://pinoutguide.com/Power/MotherboardPower_pinout.shtml

Separate troubleshooting from your definitive configuration. You can have all kinds of requirements for an ideal situation, but first you need to get everything working.

Try the ATX PSU on that board. If that works, it's a strong indication your AT PSU is the problem - and that your board, CPU, mem and VGA are good. If not, it doesn't rule out PSU problems but makes other causes more likely.

Also, what CPU are you using and what RAM - and what jumper settings have you done on the board(s)?