I built this PC back in Summer 2007 and it has been working fine until earlier this year (May 2009) when it started failing to post. (would switch on but not output video to screen, OS doesn't load as there is no HDD activity). I found a work around in turning off the psu, waiting a while, then turning it back on. The PC would then continue to work properly. However, this fault started becoming more common, then even switching the PSU off and back on still wouldn't get it posting. So i took action in the form of buying a new PSU (be-quiet darkpower pro, 650W), this hasn't solved the problem. I recently changed the motherboard hoping this would solve it (ASUS P5Q pro turbo) - problem still remains. I have had the motherboard out and tested it with just the motherboard, ram and Graphics card, sometimes it boots fine, other times it doesn't post at all. I have tried my old graphics card, inconsistently boots with that too... Eventually last week i put in a new cpu and changed the ram - still not posting consistently. Hardware: Asus P5Q pro turbo E6400 2Gb PC2-6400 9600Gt Sonic 512Mb BeQuiet DarkPower Pro 650W Recap: PC switches on, fans work, HDDs spin up, CPU fan spins up - but no consistent posting - no video output to screen. Apologies for the long post, but i am fed up with this, I have a pc which i can't consistently switch on and nothing I have done has even got me as far as working out what might be causing this. Any assistance would be very very welcome!
When you say you "changed" various components, does that mean you replaced them with the same model or did you replace them with a completely different model? (eg. were both mobos P5Q's?) I had the same problem with the exact same stat PC as you, other than a different GPU. My solution was just to build a new PC, to me it could have been so many things I wasn't prepared to find replacement parts just to check everything. Although, it did all start the day I installed Windows 7.
I originally had an abit motherboard when the problems started. Same graphics card though. I have tested with my old graphics card ATI 1950Pro, but i get the same inconsistent post failure. I've encountered this problem without any drives attached, so i don't believe them to be the cause. I'm leaning towards a memory problem as this can cause post failure, but I've tested the ram in my system with memtest86 and its come back fine... could the ram on the graphics card cause post failure??
The more components you can try as a replacement, the easier it'll be to find the problem. Having changed GPU, mobo, CPU and PSU, it could definitely be your RAM. Is your RAM 1 stick of 2gb or 2 sticks of 1gb?
Swapped the graphics card to the old one last night, turned the pc on this morning and it booted to windows fine. Turned it off and went out. Just returned and switched it on... didn't post! So the graphics card isn't the issue. I've tried two different sticks of pc2 6400 xms2, one set is 4-4-4-12 and the current set is 5-5-5-12 or 18 can't remember. I've got a pair of pc2 5400 unbranded, but i've tried all three of these sets and the problem still exists... Thanks for the responses so far!
I have reason to believe its the Power supply power cable connecting to your graphics card. It may not be be providing enough power. Had a similar problem ages ago building a friends PC, we just bought a Molex-2-PCI-E 4pin and it worked no problem. Hope this helps.
Strange as it may seem, have you tried another power cable for the PSU? I switched my main PC on the other day and there was no response. After changing the cable, all is fine. Just a thought.
ouch some expensive troubleshooting there.. I would have went with memory first- but you've pretty much replaced all the suspect parts it looks like so I'm think grounding issue with the case? take the board out and boot it off a table.. just get it to post with minimum hardware attached and start adding parts back in to narrow it down
hmmm... i agree, part of me wishes that i had just started over with a new pc, but i really want to get to the bottom of this... I tried your suggestion already, but after having bench tested it, with minimum components, the inconsistent posting/booting problem still occurred! I tried different ram and both my old and new graphics cards, but the problem still continued to rear its ugly head! Can the connection to the CPU fan cause issues (the fan starts everytime)? Its the only part of the build which i haven't changed yet. Although when the pc does boot it displays temps of less that 30 degrees!
Everything powers up fine... it just fails to post consistently, sometimes if i switch the psu off at the wall and wait a while, then switch it back on, it posts fine! Leads me to suspect that somewhere a capacitor might be shot, but then again... i've changed the mobo, the ram, the cpu and the gpu... what else could cause this? Hummmm...
I dunno zeff.. it could just be you have bad power coming in for some reason.. I mean the chances of having that exact problem with everything replaced is pretty slim maybe try a different outlet that's running on a different circuit and see if she boots.. I would say double check the wiring, but it sounds like you know what your doing, and had it running fine before all this does the machine give any beeps or errors when it posts? also look at anything you didn't replace.. even if it's not likely.. sorry wish I could be more help
Ah... beeps. Neither of my boards have an on-board speaker... so I have no idea whether the mobo's are beeping or not! Winner, i'm sure they are beeping away when it doesn't post, but I can't hear it! Grrr. Update, since starting this thread I haven't managed to get the pc to post at all... oh dear... I'm stumped and very frustrated. I think this is the most appropriate emoticon!
I've had a thought... could it be something to do with the bios battery? I'm just thinking as the fault originally appeared on my old motherboard, the battery could have been dying or dead, which might have disrupted the post ability of the mobo. I haven't tested the bios battery on the new board, i know its unlikely, but the new mobo might have been supplied with a duff battery... could that be the issue, I'll have another look at it when i get some free time... merry Christmas all!
Hi. Could it be that the CPU is overheating and just powering off? Maybe just needs new thermal paste applied :s A 2 quid syringe of paste would be cheaper than spending on more new parts.
Good thought, but when it does boot into windows coreTemp states temps of under 30 degrees for both cores over a long period of time... What are your thoughts over my bios battery idea?
What's that? your PC has issues getting up? Damn, sorry, can't help you out there. I've got no problems in that area....
Most likely. I had a similar problem with random shutdown and rebooting without any real reason. Turned out to be flaky power. UPS fixed it and got some more protection.