Thanks for your input. Chronology so far:
- Old Tagan PSU on Asus P3C mobo: unstable, would work most of the time, usually stalled on first attempt to turn machine on, would work on second attempt. Once I noticed all voltages in hardware monitor in BIOS go from nominal values to 0.0 marked in red... after a couple of days, machine turns on but no video. Replacing the Pentium II 400 with a Pentium III 1000 gets PC a little further half of the time, to memory POST, where it would always freeze on memory count. Other half of the time PC would turn off, LCD monitor detects signal, but nothing gets displayed.
- Build a new box, this time with an Asus P2B-F. Plug old Tagan PSU in, PC turns on, fans work, no video.
- Found an ATX 2.2 PSU (a Thermaltake Toughpower W0106 with cable management, 700W) and tried it on an old P4 HP mobo. Can't find the 4 pins cable that plugs in the auxiliary power connector of the mobo, so I used an adapter Molex -> 4 pins. PC turns on, fans work, no video (kinda expected that, without proper +12V 4 pins).
- Plugs ATX 2.2 PSU in old P3C motherboard. PC turns for a couple of seconds, fans work, but then shuts down. Couldn't see any video.
- Plugs ATX 2.2 PSU in old P2B-F. *Nothing* happens.
- Plugs ATX 2.2 back in old P3C. *Nothing* happens...
- Plugs it back to the P4 HP mobo. *Nothing* happens... starting to think I managed to kill 3 motherboards and 2 PSUs... getting good at killing stuff with age 😒
Plans for today:
- Will rip PSU from a PC I built for my girlfriend. Some Thermaltake Toughpower 1200W that I know for a fact is working (it's running as I write this). Will try it on the HP P4 mobo first, (this time with proper +12V 4 pins cable) then on the P3C, and then on the P2B-F. She's gonna be happy when I manage to kill her PC also. Expecting this to be my last day in this world 😵
- Will get a Tagan (same model as the one that died) for cheap, just to sort out what is working and what is dead.
Those are my tribulations so far. Sorry for the wall of text... I'm getting pretty discouraged, it's a lot of trouble for something that could be done reasonably well with an emulator on a modern PC... if you guys have any ideas, I'd be eternally in your debt if you could share them 😊
Tried with the 1200W PSU, all motherboards run without a hitch. Power management flips out because of the missing -5V, but nothing is borked motherboard-wise... gonna check out the 750W PSU... if it works my girlfriend is gonna get a PSU "update" xD
Now the Tagan works fine with the P2B-F... I'm going crazy with this stuff...
I don't know if I should discard it before it really dies and use the 1200W PSU or if I should keep it... remembers me of 2001 a space odyssey... but HAL wasn't half as mean as this PC xD