System has power, won't post. Some times.

I've been having this issue off and on for about 2 months now. It's getting to the point where i'm sick enough of it i want to take the time to fix it. Lazy i know...

This system has been together for at least a year. So this isn't DOA hardware or something. The problem occurs unpredictably and the system functions normally once it manages to POST. It may be my imagination but it seems to post after i've moved the case or smacked it out of frustration.

My system will power up, all my fans and leds come on. The HDs spin up, and stay spun up. My monitor stays in standby mode because it isn't getting a signal. No system diagnostics beeps can be heard.

I'm stumped, i can't figure it out. Nothing i can think of would occur so unpredictably. My next step is component by component trouble shooting but i'm hoping some one here may be able to save me the time. Given the unpredictable nature of my issue trouble shooting each piece of hardware could take a LONG time.

Any advice?

System spec from memory, i'll get details if needed.

Vista Ultimate 64
MSI p6n SLI (650i??) MB
E6600 CPU
4 western digital Hds. 1 IDE, 3 SATA 2 of which are raided
Rosewill 550watt PSU
4gig memory (i'd have to look to remember brand, think Kingston)
EVGA 8800 gts 320mb

Edits:

I suppose i should have mentioned earlier i borrowed a diagnostic card from a friend of mine. I had it in place when the problem occurred and it displayed nothing, no error code what so ever. So the MB isn't even getting to the start of the post process i think. I'm hoping that eliminates the MB as a source, but i'm quickly getting to the bounds of my knowledge.

I should also mention that i leave my computer on for days or weeks at a time. With no problems what so ever. It would seem strange to me then that it was a fault of the MB, CPU or RAM as i would expect these faults to interrupt long term operation. Then again i'm no expert. Leaving my system on for such long periods is part of why i havent bothered to fix this before, it simply didn't effect my use of the machine and it took quite a bit of time for me to identify this as a consistent issue instead of a one time problem.

Could be just about anything going out. First thing I would think is the powersupply, but I would first try 'reseating' everything, including power connections, except the cpu. Maybe something has come loose with all the abuse

oops, beat me to it

Thx for the thread. As for your questions. Yes to the first. As for the second I only tried that once and it did not boot up after being left alone for 5 minutes or so. I'll try leaving it alone longer soon. Just to be clear i'm not getting any diagnostic codes from the MB at all. It doesnt even get to that point.

croc:
Beat me to it. Try to borrow a better PSU. Rosewill's are about two steps above junk.

Ok better PSU is on top of the list now.

If you all don't mind playing a little House (i couldn't help the pun) could i get a differential diagnosis? If it's not the PSU what else is coming to mind?

Mind helping me understand how the VGA would completely prevent POSTing? Not questioning your suggestion as much as i dont understand it.

I'm feeling pretty good about the PSU. It's the second bad opinion i've heard about the brand. Also, when i smack the box to start it up i smack it right on top of the PSU. I may be imagining that... but something tells me it really has been the difference.

Ah, i gotcha. Well my system always beeps a bit at start up. Its not an error code just an acknowledgment. So i am pretty confident its not a display issue because i'm not hearing the normal beeps.

Alright, thanks for the help. I suppose i should have mentioned earlier i borrowed a diagnostic card from a friend of mine.

I had it in place when the problem occurred and it displayed nothing, no error code what so ever. So the MB isn't even getting to the start of the post process i think.

I'm hoping that eliminates the MB as a source, but i'm quickly getting to the bounds of my knowledge.

Hey, any news on this? I have the exact same problem with my computer, after it has been running stable for a year. Boot up, power to fans and LEDs but no post and no signal to the monitor. (it's hard to know if it actually does make a post, but since there isnt that expected start beep, i guessing it doesnt)

I was half thinking the ram could be the problem, but PSU does sound more likely. Only, I have a Hiper 770W, which I see as a fairly reliable PSU.

I just had a breakthrough on this. After reading this article from JohnnyGuru.com (thank you who ever gave me this link), I tried to start the computer with only MB and CPU, and added stuff from that. One of my four ram blocks was the sinner. It prevented the MB from doing its POST (no even a beep).

Something has to be loose, not connecting properly or shorting out. Next time the problem occurs, try to move the motherboard a bit to see if the system will power up without smacking it. The motherboard could be shorting out at one of the standoffs. What case do you have?

That site doesn't clearly show the internals, but Anandtech fortunately provides good pictures. The posts are screwed in, therefore they can't cause that problem (unless one was installed where the motherboard doesn't have a correspondig hole).

Well i spent about 2 hours this afternoon trying to figure this out. I realized one specific fan was spinning up and staying at full speed. It was distinctly louder than the others.

I watched the fans spin up and figured out it was my video card's fan (EVGA 8800 GTS 320mb). Since this was odd i wondered if the video card was the issue. I removed it and booted up my system with no video card. The system posted since i could hear the beeps.

I replaced the video card and powered up the system, no post. So wiggled the video card in the PCIE slot, next power up the system posted. I adjust the video card back tilting it towards the top of my case, no post. I tilted it down, post. It was really reliable and i could easily repeat it several times.

Thinking i had found the issue, i took a break and watched some TV. I came back about 20 minutes later and tried to replicated the up and down adjustment but it had no effect as befor. My system would post some times and not others. I unseated and adjusted the video card several times after that. I looked for anything that could be shorting and found nothing.

I may or may not be any closer to finding out what is wrong but right now my system is posting reliably. I haven't had the system refuse to post over the course of several recent attempts. Maybe i worked what ever the issue was out with all my fidgeting.

I'm hesitant to say it is fixed but at the moment i can not replicate the problem.

A short with the case is remotely possible (after all the posts are quite long), but a finely cracked motherboard should not be excluded. Smacking the system probaly makes the video card move and before doing it, you also power down the system. It looks like the combination of the moving video card and a cooler motherboard makes it work again. At least you now know approximately where the problem is.

I would clean the video card contacts (be nice and don't use anything abrasive). If that doesn't help, I would try another video card to be absolutely sure it isn't the root cause of that issue.

If it doesn't short out to the case and a new video card doesn't help, then there isn't much else that it could be. You indicated that moving the video card a bit makes the system work or fail, so it can't really be anything else than the video card or the motherboard.

system is out of the case and set up on the card board. Boots up fine, i'm typing this on it right now.

Trying to heat it up to see if that changes anything. I put pressure on the corners and booted it up several times. I figure if there's a small crack pressure may aggravate it but it has posted fine.

When i took the MB out turning it to side i could see that it had definitely warped a little over the years. Nothing major, you have to be looking for it to see it but it is definitely there.

I think it may really have been a short.

Well everything is mounted back up, it's working. I haven't been able to replicate the issue even after letting the machine heat up, and sit on all night.

When i remounted the MB i noticed i had originally used two different size Posts. I think this may have contributed to creating the short.