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New graphics card, fried motherboard

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March 5, 2012 5:20:14 PM

I was replacing my old 8800GTS with a GTX560, running on a PCIEx16 1.0 slot. 750W power supply.

I somehow reversed the 'polarity' of the molex connection on the molex-->6pin PCI adapters for my new gfx card. When I powered up, my power LEDs flashed on and off and the machine would not boot until I killed the power. The mobo no longer powers up, beeps, or anything.

This is the first time this has happened to me in over 10 years of building PCs, so I could use some advice.

Reversing the polarity on those adapters would feed the card +5v on each plug instead of instead of +12v on each plug. This leads me to believe the card was underpowered and somehow caused a surge by trying to draw too much power through the PCIEx16 mobo slot. Has anyone else seen something like this happen?

If that didn't cause the mobo to fry, has anyone seen a graphics card fry a motherboard for any other reason? Did I nuke my new graphics card?

If I somehow did damage the gfx card, can the card fry my new replacement mobo, even when hooked up correctly?

Thanks in advance everyone.
a b U Graphics card
March 5, 2012 6:00:31 PM

Just curious how you managed to jam the molex plug on backwards since it is shaped to plug in only one way? If it isn't a good PSU, you may have actually damaged the PSU. I assume you've done the usual troubleshooting tests to try and get the motherboard to POST (clear cmos, no graphics card, one ram stick at a time, etc, etc)? Do you have another PSU you can try to get your motherboard up again? Cheaper PSUs don't always have the best protection, I'd test the motherboard with a different PSU to try and make sure your PSU isn't the failed component.
March 5, 2012 6:41:53 PM

larkspur said:
Just curious how you managed to jam the molex plug on backwards since it is shaped to plug in only one way? If it isn't a good PSU, you may have actually damaged the PSU. I assume you've done the usual troubleshooting tests to try and get the motherboard to POST (clear cmos, no graphics card, one ram stick at a time, etc, etc)? Do you have another PSU you can try to get your motherboard up again? Cheaper PSUs don't always have the best protection, I'd test the motherboard with a different PSU to try and make sure your PSU isn't the failed component.


I was surprised I managed do it too, but I went back and tried it again and it offered almost no resistance. I think it's a combination of the male connections on the PSU wearing down over time (this is a 4 year old PSU and stuff has been unplugged/plugged and moved around a lot in that time) and relatively flimsy female connections on the PCIE +12v adapters.

The PSU is a 750W Thermaltake Toughpower (http://www.newegg.com/Product/Product.aspx?Item=N82E168...), and I've tested it by jumping the green and black wires on the 24Pin connector and it powers up fine as far as I can tell. I haven't had problems with the PSU in the past, but it is getting on in its age.

(Edit: yes I have tried the typical troubleshooting stuff. I have hooked up the PSU to the mobo with just the proc and 1 RAM stick in slot 1, outside the case on a wooden surface. I doesn't post or even beep at all (with the sys speaker plugged in of course)).

I don't have another PSU at the moment, unfortunately. I actually ordered a new mobo/proc/ram/psu to upgrade my system to LGA2011, but I don't want to plug in this gfx card and fry my new stuff. So I'm curious if it's safe for me to test this gfx card on my new system, or if I should just buy a new one and not risk it.
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a b U Graphics card
March 5, 2012 6:49:46 PM

mallok said:
So I'm curious if it's safe for me to test this gfx card on my new system, or if I should just buy a new one and not risk it.


Yeah, kind of a tough one. Any run-of-the-mill DOA or typical problematic graphics card the advice would be: The card isn't going to fry the motherboard. But since your mobo is dead as a result of wrong power connections on the graphics card, it's a lot tougher to say that. Best I can say is that assuming you hook it up right this time, I doubt the card would fry the motherboard. Hopefully someone else around here can be more definitive. I also doubt the card is going to work at all but keep crossing your fingers :) 

I did notice that your PSU has 2 native 6-pin PCIe power connectors. Why not use those instead of the molex adapters?
March 5, 2012 6:58:58 PM

larkspur said:
Yeah, kind of a tough one. Any run-of-the-mill DOA or typical problematic graphics card the advice would be: The card isn't going to fry the motherboard. But since your mobo is dead as a result of wrong power connections on the graphics card, it's a lot tougher to say that. Best I can say is that assuming you hook it up right this time, I doubt the card would fry the motherboard. Hopefully someone else around here can be more definitive. I also doubt the card is going to work at all but keep crossing your fingers :) 


Yeah, I'm thinking I shouldn't risk it. If I did screw up and fry my new stuff I would not be very happy. It's worth it to lose the $200 versus a small probability of losing like $800.

On that subject, do you think it would be worthwhile to try to send the (likely) dead card back? I know that it's a morally dubious thing to try to get money back for a card that I most likely fried, but it's such a 1 in a million thing to manage to reverse the molex connections that I feel somehow less responsible (even though I'm clearly an idiot).

larkspur said:
I did notice that your PSU has 2 native 6-pin PCIe power connectors. Why not use those instead of the molex adapters?


Ahem, I erm... seemed to have missed the second 6pin when I was hooking it up. I had thought I only had 1. Since it's not a modular supply I had the unused cables tied up pretty tightly and tucked away in the top of the case. Had I used those, I wouldn't be in this predicament.
a b U Graphics card
March 5, 2012 7:10:01 PM

mallok said:
On that subject, do you think it would be worthwhile to try to send the (likely) dead card back? I know that it's a morally dubious thing to try to get money back for a card that I most likely fried, but it's such a 1 in a million thing to manage to reverse the molex connections that I feel somehow less responsible (even though I'm clearly an idiot).


That would be a moral predicament that would be up to you. If you're worried about it frying your stuff maybe pay a local shop to test it (provided their fee is reasonable). If it works then you don't have to make that decision. And of course if it's dead you're out some more money...

mallok said:
Ahem, I erm... seemed to have missed the second 6pin when I was hooking it up. I had thought I only had 1. Since it's not a modular supply I had the unused cables tied up pretty tightly and tucked away in the top of the case. Had I used those, I wouldn't be in this predicament.


:na: 
March 5, 2012 7:34:49 PM

larkspur said:
That would be a moral predicament that would be up to you. If you're worried about it frying your stuff maybe pay a local shop to test it (provided their fee is reasonable).


Not a bad idea. I'll probably order a new card and then see if I can test this one in the mean-time. If they both work I can return one of them.

Thanks for your advice!
a b U Graphics card
March 5, 2012 7:38:22 PM

You're welcome, good luck!
March 5, 2012 9:27:24 PM

No one mentioned that some 2.0 cards don't work in 1.0 slots?
March 5, 2012 9:30:11 PM

jrazor247 said:
No one mentioned that some 2.0 cards don't work in 1.0 slots?


2.0 is designed to be backwards compatible with 1.0, though. And I know this card works fine in 1.0 slots, according to a few newegg reviews. Anyway, I doubt if a 2.0 card would fry a 1.0 motherboard if it wasn't compatible.
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