Computer doesn't start when graphics card plugged in

Symptoms: after changing heatsink on graphics card, computer won't turn on when graphics card is plugged in PCIE slot. When I press the power button, fans move a little bit and that's it.

The card is XFX Radeon 6850. With the card not plugged into motherboard, but plugged into power, computer boots. With the card in motherboard, with or without power, it doesn't.

The heatsink was Arctic Cooling Accelero S1Rev2. It was a tight fit, and I had trimmed some of the heat spreaders to get them to fit. When testing with Furmark one of the temperatures was much higher than others, so I decided to reapply thermal paste. After doing that was the last time the system successfully POSTed, it went like this: BIOS screen came up, GRUB came up, Windows started loading, and then the screen went black, all fans stopped, and the power LED started flashing. It continued flashing even after I disconnected power cord from PSU, and stopped at the moment I disconnected monitor.

I took the heatsink off the card again to check for obvious shorts, put it back together, still the same.

I understand that the card may very well be dead now--maybe thermal paste spilled somewhere, maybe static electricity hit at some point, maybe heatsink touched something it shouldn't have, or maybe just not delicate enough handling. Anyhow, given the symptoms, what would be your guess what's gone wrong?

Solution 1:

This sounds like the GPU on your card is fried. This is very similar to how CPUs fry when you don't fit the heatsink properly. You will turn on the PC, it will maybe get as far as booting into Windows if you're lucky, then it dies as the CPU overheats.

The same thing will happen with a graphics card GPU, so unless you are 100% sure the heatsink was seated on the GPU, it has probably overheated and fried.

By the way: Maybe thermal paste spilled somewhere. This wouldn't do anything as it isn't conductive – well unless it is silver compound – and even then it is only slightly conductive so wouldn't make any difference. The worst it would do is slow things down slightly or cause artefacts.

Maybe static electricity hits at some point – static is a possiblity when you had the card out of the system. If it struck the memory on the card this wouldnt do it much good.

Maybe the heatsink touched something it shouldn't have. This is the most likely thing that happened. If you have ever fried an old harddrive on purpose when you were younger, if you cross any of the circuits on the drive it doesn't tend to die straight away, it usually takes a few seconds before things heat up enough for it to cooks an onboard chip and dies.

Or maybe just not delicate enough handling (possibility again, but I think the above is more likely).