Can P.S. lock up motherboard?

[flyted]

Antec LS400. Homebuilt computer that has worked fine for years, then a month ago started not wanting to shutdown and would reboot at the last second. Couldnt fix the problem and now the computer can only be turned on via the ps and then no video, no HD noise, just the fans and the green MB standby power light. All the voltages appear nomal on the ps now and I monitored them before and they were all within a few%. The video card fan was not turning, dont know if it ever did or is temp controlled. Need to start replacing parts as I have nothing to swap out and try. So far cant find a way to test individually the video card, MB and ps, although the ps seems ok. Any ideas?

Thanks

 

[IEC]

Do you get any sort of POST beep codes?

What model is your PSU/how old is it?

Do you have an old PCI video card you can use/borrow to test with?

I recently replaced a failing Antec True430 PSU (it ran for almost six years!) with a Corsair TX 650W and the occasional spontaneous reboot/lockup at full load has disappeared completely.

 

[flyted]

No beeps or noise at all, don't even hear the HD do its thing.

Itsa Antec LS400, 4 years old and its had a perfect life being on a high-end surge protector, line conditioner and UPS its entire life. In addition its in a SOHO case with excellent cooling, it could ask for better living conditions, but that doesn't mean its not faulty now, just can't see where.

I don't have a spare video card of any kind, nor a MB. I may be able to find a used ATX ps.

As a last resort to not being able to identify the bad part, I could just get a MB/cpu combo on the cheap with built in video and maybe use my memory sticks, however I'd love to keep my AMD XP-2800 as I love it along with my 2GB ram, if possible.