Hard Drive, no... Power Supply, no... what's the issue!

So, looking for a little verification of what I need to do here! System in question is the one in my sig... and here's what's going on.

Symptom is this ... push the power button, machine comes on, fans run, no beeps, no bios... black screen. Heard the hard drive doing a bit of a click, click thing so got a new one. Put it in and seemed normal'ish, got Win 7 loaded but very quickly it started acting odd, checked using SIW and power supply 12V rail looked to be bouncing all about ... it would generally read fine, then drop to 8V ... the back up and normal, then up to 13.5v, down to 7.xxV, back to normal. After a shutdown it started with the original symptom ... power on but no go, no bios, no boot from CD blah blah blah. So, turned it off and ordered up a new power supply.
The original was a Rosewill 500w I believe ... ordered and received a Corsair 650w PS so all jazzed! Put it in and my original hard drive as boot considering that it was probably good all along and fired right up, very cool. Did a number of things, worked with the machine for the day and got the other hard drive formatted and such so now a bunch of extra storage and such! Did check SIW and the 12V rail is exhibiting the same odd behavior but the machine seems to be running fine. Ran some stress tests and such to see if it would mess it up and all was good. Shut it down for the evening and it's been that way since then... a couple of three days ago.
So, what's the deal! I put in a new battery in case it was some oddball thing like that and no difference, back to the original issue of power on and you've got power but nothing else ... no beeps ... no progress.

So, ideas??? I'm thinking it's the motherboard that's causing the flux in the 12V rail but looking for some confirmation of that possibility.
TIA ~ Paul

It does sound like a motherboard issue. Check the board carefully for leaking or bulging capacitors.

See this link for other users reviews:
http://www.newegg.com/Product/Produc...-070-_-Product

I think it's most likely the motherboard too. But I would try disconnecting everything that uses a 12volt supply that you possibly can, fans, optical drive, etc. just to make sure that you don't have an intermittent short somewhere that's pulling that rail down.

Yeah, I've been checking for capacitor issues but all looks good...
And will try that Sparks and see if that tells me/us anything... will post back when I have some time to check it... trying to do the sell & buy a house thing so we're going pretty insane here. ;-)

Well ... no rest for the wicked... no luck on the disconnect of various/all 12V devices and such. So, new motherboard it seems ... any suggestions for a replacement? Looks like many of the motherboards at Newegg are going micro atx ... been too long, now I have to do some research! ;-)

Is it the one in your signature?

The machine that's having the issue? Yes, the one in the sig ... so basically looking for socket lga775 ... ddr2 type board.

There are still quite a few to choose from, depending on what options you want. Make sure the one you select will take your DDR2 800 memory.

http://www.newegg.com/Product/Produc...NG&PageSize=20

yup ... went with this offering...
http://www.newegg.com/Product/Produc...82E16813131615
It'll get me by until the next big build I'll hope...
I just hate that I'll have to reinstall the whole mess! Or do you think Windows 7 will figure it all out and work some magic? ;-)

IS it possible that the PSU may have a problem.. seen many a HDD and Motherboard killed by a faulty PSU.. the variable voltage.. while can be a bad MoBo.. but a Bad PSU can give exactly the same symptoms.. If I saw that level of variation in the 12V rail first thing in would be my Test PSU .. then check for more problems..
You could put a brand new mobo in there and if the cause is the PSU you will be looking for a replacement with in the first 48hrs..

With Windows, all you can do is try - sometimes people get lucky after a mobo replacement and it boots fine. If not, a clean reinstall is best, though you can "upgrade" Win7 over itself instead, which should work OK.

PSU's already been replaced und3rtak3r...

And so ... new MB in and rebuilt. Power on. Same thing... DVD light blinks, HD light comes on, fans spin... no beeps, no go.

So, pull the TV card just to start getting things eliminated from the equation... did that and machine come on and all is good. Win 7 once booted goes through and finds all the new drivers and such, really do love Win 7! And so I look about.... power levels all look good ... well stable lets say. SIW, is showing a steady 7.62 on the 12v rail though. So I check using speed fan and Asus Probe and they both read 12.5, solid. Along with all other things ... looks good. Ran some stress tests, Prime95, and temps are solid and machine runs well.
So, let's put that TV card in and see if it's still messed up... nope... card's back in and working fine so all's good. For a few days... turned it on this evening and same thing. A few lights come on and fans too... no beeps, no go.

I'll tell you what ... I've built too many machines to count and this is the first time I've seen this one. All I can figure is a short in the case wiring maybe ... I suppose the CPU could be a problem but doubt it as the stress tests all went fine.
I'm at a loss....

And ... noticed a bad thing on the old MB that I pulled. It's obviously not bad as the new MB is exhibiting that same issue. One of the pins on the socket, LGA 775, looks to be bent, possible to bend it back???

I'm about burnt out on this one. TIA

If you are really careful, you may be able to bend the pin back. I would use some fine, smooth jawed needle nose pliers to try this.

yeah, I hear ya jdc ... need one of those magnifying glasses with the light and such too I'd say. But will pass on the needle nose of any variety... maybe a very narrow straight pin possibly, get under it and bend it up ever so gently.

But for now it's time to do a bit of work on the machine that's twitchin' here and see if I can't figure out what's causing the issue. It's a real puzzler for sure. I'll post back tonight if I find anything.

At this juncture, I think I'd try pulling the mobo out and laying it on some insulating material. It does seem like there's a short somewhere :(