Sons computer will not post

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Sons computer will not post

Post by bluntspoon » Thu Jan 01, 2015 11:21 pm

Was going to change out the dvd drive in my sons computer, saw it was dusty and decided to take it outside and go at it with compressed air. When I brought it back in it now won't even post. Have cleared CMOS a couple of times, changed the battery on the MB, pulled all components and hit with compressed air and reseated, including cpu heatsink/fan. Decided maybe the stock heatsink/fan was not connecting properly anyway and changed it out, no change. Went down to a single stick of ram, tried multiple single sticks etc, no dice.

Will.not.post.

When I press the power key the two case fans start up but it takes the cpu fan a few seconds before it kicks in. This may not be normal but I'm not positive. There is power to all fans, including video card but that's as far as it goes. Cannot even get to BIOS.

PSU is a Corsair VX550.

I'm open to suggestions.
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Re: Sons computer will not post

Post by eumoria » Thu Jan 01, 2015 11:35 pm

The CPU fan not starting immediately is normal on newer systems.

Did you try resetting the BIOS? There should be a clear CMOS jumper somewhere on the board. (EDIT You did that I can't read)

Anyway barring that you may have blown dust/crap behind the motherboard and it's shorting pins. The power supply won't allow the system to post if it detects a short on a rail. For odd gremlins I usually just give up and dismantle it entirely and start from clean scratch.

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Re: Sons computer will not post

Post by bluntspoon » Thu Jan 01, 2015 11:54 pm

eumoria wrote:The CPU fan not starting immediately is normal on newer systems.

Did you try resetting the BIOS? There should be a clear CMOS jumper somewhere on the board. (EDIT You did that I can't read)

Anyway barring that you may have blown dust/crap behind the motherboard and it's shorting pins. The power supply won't allow the system to post if it detects a short on a rail. For odd gremlins I usually just give up and dismantle it entirely and start from clean scratch.
The new heatsink/fan required me to remove the MB to place a bracket behind it so I did essentially have to remove everything and rebuild from scratch with no change.
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Re: Sons computer will not post

Post by bluntspoon » Thu Jan 01, 2015 11:57 pm

And yes I know it's going to be the PSU but I buy decent ones so this doesn't happen and it's just going to piss me off.

So tell me what else it could be so I don't have to be angry. :)
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Re: Sons computer will not post

Post by eumoria » Fri Jan 02, 2015 12:29 am

:( have another power supply to test with?

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Re: Sons computer will not post

Post by M's » Fri Jan 02, 2015 7:24 am

Mine was doing the exact same thing. And I had to replace the MOBO.

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Re: Sons computer will not post

Post by Boss Llama » Fri Jan 02, 2015 7:43 am

HSFs with back plates are tricky! The plate is needed, obviously, to support the HSF, but the installation process is risky for the mobo. I'd suggest pulling the rear panel off the case and ensuring the plate is attached completely level to the back of the mobo, and making sure it does not come in contact with any of the frame, mobo pins, or the rear panel itself when the case is closed up. Inspect closely as well to make sure the mono hasn't cracked anywhere, either from the installation process, or just from the sheer weight of the large HSF being put on it - some mobos just aren't designed to handle that kind of stress.

If that's all clear, check that the CPU is fully set and is locked down correctly by the HSFlocking mechanism - if it's able to move even the slightest amount when your case is upright, it'll slip out of place and things won't work. Check power cables as well to ensure every last one of them is in, especially the motherboard power cables! It's easy to forget the 2nd mobo power cable. Also, ensure the HSF fan is plugged in to the fan power port specifically designated for the CPU fan. If it isn't, the system will fail to detect it and won't POST, even if it's plugged in somewhere else.

Last thing I can think of at the moment is to check carefully that the mobo isn't warping while upright from the weight of the large HSF. If it is, it could be coming out of contact with a less flexible part somewhere, like the CPU or a power connector, that is otherwise fully set. If it's a gaming board and has all of its screws in, this shouldn't happen, but worth checking.
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Re: Sons computer will not post

Post by bluntspoon » Sat Jan 03, 2015 9:03 am

Alizée Fan wrote:HSFs with back plates are tricky! The plate is needed, obviously, to support the HSF, but the installation process is risky for the mobo. I'd suggest pulling the rear panel off the case and ensuring the plate is attached completely level to the back of the mobo, and making sure it does not come in contact with any of the frame, mobo pins, or the rear panel itself when the case is closed up. Inspect closely as well to make sure the mono hasn't cracked anywhere, either from the installation process, or just from the sheer weight of the large HSF being put on it - some mobos just aren't designed to handle that kind of stress.

If that's all clear, check that the CPU is fully set and is locked down correctly by the HSFlocking mechanism - if it's able to move even the slightest amount when your case is upright, it'll slip out of place and things won't work. Check power cables as well to ensure every last one of them is in, especially the motherboard power cables! It's easy to forget the 2nd mobo power cable. Also, ensure the HSF fan is plugged in to the fan power port specifically designated for the CPU fan. If it isn't, the system will fail to detect it and won't POST, even if it's plugged in somewhere else.

Last thing I can think of at the moment is to check carefully that the mobo isn't warping while upright from the weight of the large HSF. If it is, it could be coming out of contact with a less flexible part somewhere, like the CPU or a power connector, that is otherwise fully set. If it's a gaming board and has all of its screws in, this shouldn't happen, but worth checking.
Check on pretty much all those. I cannot see directly behind the MB to see if the screws from the back plate are touching anything but everything else is squared away. I'm going to try resetting the CMOS again.

Edit: Computers are weird. It fired back up on the CMOS reset. Who then hell knows at this point. Just happy it's going.
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Re: Sons computer will not post

Post by metacide » Wed Jan 21, 2015 9:26 pm

I'm glad it wasn't the mobo! Typically when a power supply goes bad it takes the mobo with it. Seems like in your case there was a short which (thankfully) didn't fry anything but prevented the mobo from fully powering on and your tinkering caused something to move out of the way.

I would be careful about just letting it go without knowing how it shorted out. It's possible that whatever caused it before will cause it again, and if it does it while the PC is fully powered you could be looking at a terrible failure.
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Re: Sons computer will not post

Post by The_Reaper » Tue Jan 27, 2015 6:34 pm

metacide wrote:I would be careful about just letting it go without knowing how it shorted out. It's possible that whatever caused it before will cause it again, and if it does it while the PC is fully powered you could be looking at a terrible failure.
I agree. I almost shorted my first laptop to death when an improperly seated new video card caused the fans to short. Check everything you've changed to make sure everything is tight and touching nothing it shouldn't, and if you used new screws or bolts make sure they're not too thick for the space.
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