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Dual Power Supplies not working as expected

Tags:
  • Power Supplies
  • Graphics Cards
  • Dual
  • Homebuilt
  • Systems
Last response: in Systems
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January 13, 2014 6:49:39 PM

Me and my buddy have a litecoin miner with 4 Radeon 6970s. We didnt realize this at first but we have a 1000W psu and it doesnt quite deliver enough juice to run all 4 video cards, once the fans started spinning it would turn off within 10 seconds. So we removed 1 of the video cards temporarily until we could come up with a solution. We ordered a Lian-Li dual power supply adapter ( http://www.ebay.com/itm/Dual-PSU-cable-Secondary-Power-... ) and a 700W power supply. After hooking it all up we noticed that the OS wasnt detecting the 4th video card so I did some investigating and discovered that the 2nd power supply isnt even turning on.

We have the setting in the bios so that the computer turns on automatically without having to push the power button because we have no power button it is running in a homebuilt open-air case. I turned both power supplies off and then turned on just the 2nd power supply which is only hooked up to the 4th video card and the dual psu adapter. I then turned on the main power supply and the 2nd power supply turned off and the PC powered on. Why is this happening? is there a good reason why the 2nd power supply turns off when you turn the first one on? Help greatly appreciated :) 

More about : dual power supplies working expected

January 13, 2014 7:10:30 PM

I wouldn't even run the dual connecter. Just plug in the PCI-e and go.
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a b ) Power supply
a b U Graphics card
January 13, 2014 7:22:05 PM

you can try it with just bridging the correct connectors on the 2nd PSU.
try disabling the auto on feature and turning the motherboard manually, (using the dual PSU adapter) bridge the power switch pins on the motherboard.
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January 13, 2014 7:39:35 PM

HugoStiglitz said:
you can try it with just bridging the correct connectors on the 2nd PSU.
try disabling the auto on feature and turning the motherboard manually, (using the dual PSU adapter) bridge the power switch pins on the motherboard.


ill try that tonight before i go to bed, also what exactly do u mean by "bridging the correct connectors on the 2nd PSU"? Do u mean for me to hort the two pins that connect to the dual psu adapter?

Update - So I disabled auto-on in the bios and the same thing still happens, secondary power supply turns on for a second when I start the computer up then it turns off and the computer boots up without it and doesnt detect the 4th video card.

So I switched out the secondary power supply with the 500W power supply I have in my computer and the power supply starts up and runs fine. All 4 video cards are detected when the OS boots up. Then once the fans on the video cards get up to speed it runs for about 15-20 seconds and then turns off with no warning, which is exactly what was happening when we were only using 1 power supply, anyone know what this could mean? All the video cards are plugged into the motherboard via PCI-E Risers, we have 3 hooked up via 16x to 1x Risers and 1 hooked up via a 16x to 16 Riser.
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