help on modular PSU cables to PCI-e

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holograch

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Feb 22, 2017
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So I have a 750w Chieftec modelnumber: CFT-750-14CS

So first off I need to power a sapphire HD 7970 which uses two 8-pin connectors for power. I got the chieftec PSU used and without all the original cables. I have one original (PSU side) 8-pin to (pcieside) 6pin that has a converter to 8pin. now thats one slot down and ready. I only have one of these original cables though and I've read a lot of places that I cant use a cable from another modular PSU (which I have laying around from a CM PSU). So since its difficult to get another original cable shipped out here fast I was thinking of maybe using a molex to pcie 8 pin converter but I only have female molex plugs because once again, I dont have all the cables for the PSU.

Also the PSU has these colorcoded outputs named v3 and v4 and I can't figure out what they mean because I dont have the manual. Does anyone here have any ideas on how I should power the other slot? it seems that its possible to I might have to just order the cable but I'd rather discover other options first. any ideas?

pics: http://imgur.com/a/VyREe
 
Solution
clutchc
The receptacles marked V4 are for the Molex cables. Yes, you can use the Molex to power the second header on the card with an adapter, if you have to.
As to the all black cable, if you have a voltmeter, plug it into the PSU and read the polarity at the 6+2 pin end. Or if the wires are all exposed, follow them from end to end and compare them to the good cable you have.
Yes, the 8 pin cable you found sounds like the CPU cable. The polarity is the reverse of the PCIe cable.
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clutchc

clutchc

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If you have a cable from another PSU, first check to see if it fits the chieftec receptacles. If so, check if the polarity is the same between the chieftec cable and the spare cable. The positive (+) wires should be on the smooth side of the connector at the GPU end, while the negative (-) wires should be on the side with the clip. http://media.bestofmicro.com/Power-Supply-Fundamentals,8-K-312644-13.jpg The extra +2 wires will be redundant grounds for stability.
If so, you should be able to use it.

On your PSU, the red receptacles are the PCIe and the 6-pin black are the aux Molea and/or SATA power cables. The 8-pin black is for the CPU 4+4 pin header.
 
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holograch

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Feb 22, 2017
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So I've been digging through my PSU cables and I have one 8pin to 8pin cable but it doesnt say pcie on it so it might be for an 8pin cpu. the yellow cables are on the side with the clip and the black cables are on the smooth side which doesnt correspond with the diagram you posted a pic of. I found another cable that has 8pin to 2x6+2 pins which might actually belong to the PSU but these cables dont really have any numbers or names engraved in them so its hard to tell. This cable is also just pure plack and not black and yellow so I cant tell whats + or - on it.

if I did run one pcie cable 8pin to 8pin (which I have one of) and then use molea with an adapter to pcie 8 pins (which they sell at the local computer shop) it would make sense to me to make sure all these cables were plugged in v4. example using the pcie plug at the psu that says V4 on it, and using like the 6pin card reader to hook up the molea because then everything is running on the V4. I'm a bit cautious of trying this out just yet though because I dont want to fry anything by using the psu wrongly.
 
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clutchc

clutchc

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The receptacles marked V4 are for the Molex cables. Yes, you can use the Molex to power the second header on the card with an adapter, if you have to.
As to the all black cable, if you have a voltmeter, plug it into the PSU and read the polarity at the 6+2 pin end. Or if the wires are all exposed, follow them from end to end and compare them to the good cable you have.
Yes, the 8 pin cable you found sounds like the CPU cable. The polarity is the reverse of the PCIe cable.
 
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