Last night I tried a couple of things I wanted to try before buying a new PSU:
1) Unplugging the power button connector and doing the screwdriver test, to rule out a bad front-panel switch. No difference.
2) Followed the MB manual's procedure for clearing the CMOS data. Well, I think. It said to unplug the power, but it wasn't clear if they meant cord and PSU socket, or cable and MB socket. I did both, moved the little bridging dohickey for > 5 sec, moved it back, and voila! PSU stays on!
So I reconnected everything, and everything spun up, but the PC didn't do anything, just sat there. MB manual's troubleshooting section, first item was "if no beep, your cpu and mobo aren't working together". OK, so pull the "cpu+heatsink+fan on a card" contraption out and put it back in. (BTW, I'm doing all this with the 3-prong power cable plugged in and touching the metal case often.) This time it seems to go in farther. The flexing of the mobo and some creaking/cracking sounds make me nervous. Power on again, and I get a single beep! And I see and hear it hit the CD drive and floppy drive, as part of the normal startup procedure. Awesome, except one minor little thing -- I have absolutely no video. And nothing in the manual about that.
And unfortunately this morning before work I tried clearing the CMOS again. Maybe I nudged the CPU card trying to pull the mobo power connector out, because now I'm back to the damn PSU shutting off 2 seconds after starting up!
I'm really just about ready to go Office Space on that machine -- it's effectively giving me the "PC LOAD LETTER" and the finger, and I want to smash it to bits. I don't know how some of you guys do this as part of your jobs. I definitely don't have the temperament for it. Nor the manual dexterity, nor the years of experience to know what to do and what not to be fooled by. I am *so* in way over my head here. For yucks (not really) I went to the Geek Squad web site, to see how much for diagnostic and repair, but it's $200 to bring it in, and then it only talks about OS issues and malware removal. This is for grandma, and her virus-infested Windows 98 machine, not me.
Okay, so before blowing a fuse, any idea how to get the video to display? (The monitor and cable are less than 6 months old.) Assuming the stars magically align once again and I can get it back to staying running again -- I guess I'll try reseating the damn CPU assembly again. The (PCI, and very early, initial GeForce model) video card got put back in the same slot it came out of, for sure. I have an old ATI ISA video card from my 90 MHz Win95 machine that I could try instead, if someone thinks maybe I somehow blew my video card. This mobo does not have any on-board video.