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2 PSUs to power one GPU?

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By 153494661273805047288
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Hey guys, so I have an old system, a box of old power supplies, and an HD6870 that I got from a friend. Sadly, none of the PSUs have the required two 6-pin PCIe connections to plug into the 6870 - the 350W PSU originally in the system has none, and I found two 250W that both have one 6-pin each. I tried to redneck-together this setup.
 
I plugged in everything on the motherboard along with one of the 6-pin ports on the GPU with one of the PSUs that I found in the box. The other PSU I found in the box only had its 6-pin PCIe connector plugged into the other port in the GPU, and nothing else was connected to it. However, when I plugged them both into the wall outlet the system's power button started flashing yellow and would not turn on.

 

Instead, I tried to plug everything on the motherboard in with the old 350W PSU that was originally in the system, and used the other two's 6-pin connections to plug the GPU only. This time the system powered on, the GPU fan spun, and I even heard the BIOS beep - however nothing was displayed on the screen. What do you think the problem could be? Is this even possible? Is the GPU fried? (could be, friend said his PSU died and it might have affected the 6870 he gave me). Oh and no, I don't have any money to buy a Molex to PCIe, less so a new PSU.

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Remember you need to start the other PSU's by shorting the (usually) green lead to a black one on the motherboard connector.

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Yeah, that means there's no video from the card. Is the PSU not plugged into the motherboard actually on?

 

You need to short the green wire to one of the black ones to start it:

 

atx-power-on.jpg

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I see, I didn't think about it not starting by itself and having to short it first. So do I have them plugged into the GPU and then short it with the ATX plug or should I do that first and then connect them to the GPU?

 

EDIT: Never mind, watched Face2Face's video, very helpful! Thank you very much guys, I will try this tomorrow and see if it works. Strange how the fan still turned on even though I didn't short either of the PSUs connected just to it.

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I see, I didn't think about it not starting by itself and having to short it first. So do I have them plugged into the GPU and then short it with the ATX plug or should I do that first and then connect them to the GPU?

Have them connected all the time.

My PC CPU: 2600K@4.5GHz 1.3v Cooler: Noctua NH-U12P SE2 MB: ASUS Maximus IV RAM: Kingston 1600MHz 8GB & Corsair 1600MHz 16GB GPU: 780Ti Storage: Samsung 850 Evo 500GB SSD, Samsung 830 256GB SSD, Kingston 128GB SSD, WD Black 1TB,WD Green 1TB. PSU: Corsair AX850 Case: CM HAF X. Optical drive: LG Bluray burner  MacBook Pro, Hackintosh

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Should I be careful not to touch the paperclip while the system is on then? It can't electrocute me, right?

Yes i can. Dont let the paperclips touch each other either. 

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Should I be careful not to touch the paperclip while the system is on then? It can't electrocute me, right?

12 volts really is not enough to electrocute you. the voltage is not high enough to break the resistance of your skin so you don't have to worry much about getting shocked.

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12 volts really is not enough to electrocute you. the voltage is not high enough to break the resistance of your skin so you don't have to worry much about getting shocked.

 

 

I agree, though I just want to point out, its not all about how many volts something has. Its the combination of volts and amps that hurt. Theres a good video on youtube of it, I forget what its called and it went over my head so thats really the only thing I took away from it.

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You should be able to take a different cable that comes off the power supply and splice a 6pin connector onto it.  yellow wires are 12v, black are ground.  However use two molex connectors to pull from two 12v wires, not just one.  If you don't know what splicing is, don't attempt it.  I don't want to be responsible for you blowing stuff up.

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I agree, though I just want to point out, its not all about how many volts something has. Its the combination of volts and amps that hurt. Theres a good video on youtube of it, I forget what its called and it went over my head so thats really the only thing I took away from it.

yep amps are the killer. Thats why a 120 volt wall socket can be deadly where as a 15,000 volt static shock is harmless.

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Well, I tried it, and still exact same problem. Even without the two PSUs the GPU gets power from the PCIe port and that's why the fan spins, but with them plugged in or not nothing happens on the screen. I did the paperclip thing on both. Sadly they don't have fans or any indicator LEDs so I've no idea if it worked or not. I think I know what the problem is though - for some reason the 6-pin connector barely fits in the port on the GPU, in fact, I'm not sure the contacts are actually touching.. At first I thought it was in contact since the fan was spinning, but now that I know it spins from the PCIe port, I think it's not connected. The little clip doesn't snap on, because I can't push it far enough in. I looked it up and the plug looks exactly like it should, some of the wires have square plastic covering around them, others have D-shaped plastic, but it's all in the right places. And it goes in, just not until the very end. Should I try to cut the plastic around the top a little?

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Well, I tried it, and still exact same problem. Even without the two PSUs the GPU gets power from the PCIe port and that's why the fan spins, but with them plugged in or not nothing happens on the screen. I did the paperclip thing on both. Sadly they don't have fans or any indicator LEDs so I've no idea if it worked or not. I think I know what the problem is though - for some reason the 6-pin connector barely fits in the port on the GPU, in fact, I'm not sure the contacts are actually touching.. At first I thought it was in contact since the fan was spinning, but now that I know it spins from the PCIe port, I think it's not connected. The little clip doesn't snap on, because I can't push it far enough in. I looked it up and the plug looks exactly like it should, some of the wires have square plastic covering around them, others have D-shaped plastic, but it's all in the right places. And it goes in, just not until the very end. Should I try to cut the plastic around the top a little?

 

I wouldn't. Can you post pictures of the sockets on the gpu and all the psu plugs that look close to fitting?

80+ ratings certify electrical efficiency. Not quality.

 

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I wouldn't. Can you post pictures of the sockets on the gpu and all the psu plugs that look close to fitting?

Sorry, I don't have a camera, but I can tell you it looks exactly like the left one in this picture: PCIEPOWEXT_1600x1600.jpg

The top-right and lower left pins are square, as you can see.

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Hmm, after a bit of looking around, I think it might have been just a 6-pin motherboard plug.. I will try to solder together some Molex connections to the PCIe plugs from my friend's fried PSU.

 

Which is less expensive, buying a new psu or buying a new psu and replacing the gpu (and potentially the motherboard)?

80+ ratings certify electrical efficiency. Not quality.

 

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Have no experiences with this but:

500x1000px-LL-d09ecc70_LianLi24split.jpe

Shouldn't a 24pin y splitter just work fine? Connect one cable to one psu and another one to the other psu. Feel free to correct me if this wont work.

This will work.

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Have no experiences with this but:

500x1000px-LL-d09ecc70_LianLi24split.jpe

Shouldn't a 24pin y splitter just work fine? Connect one cable to one psu and another one to the other psu. Feel free to correct me if this wont work.

That should work. It's basically signaling the secondary psu to be powered on at the same time as the other via the green wire.

 

 

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