PC Won’t start up

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I switched my PC on today, it ran for about 5 seconds then powered down.
It was OK last time I used it.
My first thought was processor failure, or power supply problems, because I wasn’t even getting into the BIOS, but the fans all started OK. I then tried unplugging the power connector for the graphics card (the 12V ATX 4 pin connector).
The PC then started and ran, but obviously I couldn’t see any output so I eventually unplugged it.
The graphics card fan was running OK in both cases.
My motherboard is an ASUS M2N32-SLI, and the graphic card is an NVIDIA GeForce 6600 PCI-Express.
The power supply is 550 watt rated, and I have had no previous trouble at all, certainly no overheating problems.
Anybody got any suggestions, especially regarding whether to swap out the graphics card or the power supply first.
TIA
Alex

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Since the PC powered down it would seem more likely to be a power supply. Without additional testing it is really hard to tell.

Before replacing anything I’d check all the connections to the video card. Then try turning the PC off again. See if it starts OK.

Joe

--Joe

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Thanks, Joe,

I tried the card in the second PCI-E slot with the same results.

Like you, I thought power supply first, but then it ran OK when I unplugged the 12v connector.

Pity the motherboard doesn’t have an AGP slot, I have a spare one I could have tried.

Alex

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Hi Alex,

Look in the BIOS if you are able to do so, to determine if your motherboard has a built in graphics adapter. If it does, enable it, and remove your PCI-E video card from the PC and reboot. That could tell you if your PCI-E card has given up the ghost.

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You can pick up a power supply tester pretty cheap @ any radio shack.Here in the states it only cost around $15.00 us.

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This is a toughie. No video and no integral graphics adapter! I suggest that the easiest diagnosis is to see if you can ‘borrow’ a basic PCIe graphics adapter from someone – a low powered device that doesn’t need any auxiliary power connection.

I think it may be the graphics card rather than the PSU because ordinarily, if you try to boot a PC without the auxiliary power connected to the graphics card, you should get a system bleep and an on screen warning message. The absence of bleep or warning when you boot without the connection suggests a sick graphics card.

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I ‘borrowed’ a similar NVidia PCI-E card and put that in – with exactly the same result.

I’ve now ordered a new PSU!

Thanks for the suggestions, guys

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Good luck. Let us know the results.

Joe

--Joe

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New 650 watt PSU installed – exactly the same problem.

I’m stuck for ideas now.

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Is the mobo booting correctly? TerFar noted that there should be beeps, but it’s not clear if you have any, or if it’s a motherboard that is not booting.

When you removed the aux power connector from the gfx card and the system “ran”, were there beeps and genuine signs of life, or was it just fans spinning etc. -> did system boot and attempt to load the OS under these circumstances. Did the HD spin up and load the OS, was the num lock on the keyboard illuminated? If not, then do you get these normal signs and symptoms when you remove the gfx card completely?

Given that you have replaced the PSU, absence of beeps or other normal signs and symptoms when the gfx card is not installed suggests a dead motherboard.

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I decided to go go back to basics – no other option really.

I took the m/b out and ran it with just the GPU and memory. Started OK, so I put it back in the case, fingers crossed there were no shorts. Ran OK, so I started adding items back one at a time, checking for starting each time.

Eventually everything was back in place and is now running OK. I’ve no idea what the problem was, suspect a short of some sort, but can’t confirm it.

Anyway all’s well that ends well, thanks for all the advice.

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Had to be some type of seating problem. These type problems can be very intermittent, and can be very difficult to find. Some many things can cause components to become unseated, from heat to vibration. Reseating components is one of the easier trouble shooting things to try. Glad your problem is solved.

After T/S electronics for many years in the Aerospace industry, we always tried to reseat components properly before replacing them. Simple but effective technique.

The other thing that happens is that contacts get minor amounts of corrosion or foreign substance on them which causes similar failures as unseating although they tend to be even more intermittent. We used to have pencil erasers that sometimes did a fine job of cleaning contacts.

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