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PSU Do I trust this Corsair Type 3/4 Pcie Cable?

Discussion in 'Hardware' started by malccy72, 10 May 2020.

  1. malccy72

    malccy72 Member

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    hi

    really hope someone can give me a clear answer on this one. Am using a second-hand Corsair 750w psu (TM) for almost a year now and all is good but wanted another pcie power cable as it only came with one and heard to use two cables from psu if gpu had two 8 pin connectors required. I have ordered and received one but when I checked the pin layout compared to the existing one plugged into the psu I notice that the 'empty' pin in the new cable is different - the new cable its 'bottom-right'.

    Weirdly I checked the Corsair site before I bought cable and it says 'type3/4' are same and looking at other sites with pictures I can see the new cable I have bought is the same as everyone is selling but why is my existing pcie power cable layout different to my new one?

    I dare not connect the cable to my psu until I feel it is safe to do so.

    Thanks for help.
     
  2. BeauchN

    BeauchN Active Member

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    Can you provide the exact details of your PSU and the cable you bought?
     
  3. malccy72

    malccy72 Member

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    Sorry, I have a Corsair 750watt tm model. The already connected pcie power cable (6+2) is a different pin layout than the one that I have bought but looking online the pin layout of all the type 3 / 4 corsair psu pcie power cables are the same as the opne I have just bought and not like the one already connected.
     
  4. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    The empty pin should be on the PSU connection side of the cable as all the pins on the device side should be populated.

    The PSU connection should have 4 x 12V pins and 4 Ground pins. Only 3 of the 12V pins will be used so one of the pins will not be populated.

    The 4 Ground pins on the PSU side will have 1 wire branching into 2 on the device side as 5 pins are required to be populated.

    The image here shows the device side and the PSU side of the connectors. If you orient your old and new cable to match the image with the 'latch' at the top you should see that the missing pin on each cable corresponds to the 12V (yellow on the diagram). As long as it's a 12V pin missing on each one on the PUS side it doesn't matter which one is missing. If the new cable's missing pin doesn't correspond to any of the 12V pins then don't use it.

    A perfect double check is a PSU tester but the only one I'm aware of that tests the 8 Pin PCI-E cable is the Thermaltake Dr Power II which I don't think is made anymore and the few examples for sale are at rip off prices. I'm reluctant to loan you mine as it's pretty much irreplaceable except at too high a cost.
     
  5. bawjaws

    bawjaws Well-Known Member

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    Is it a TX-750M or an RM750? I can't see a "TM" series listed on Corsair's website

    A bit of Googling (paying careful attention to the image for "Type 3" PSUs, not the one above for AX PSUs) suggests that Corsair type 3 & 4 cables for PCIE power have 4 +12V pins and 4 grounds, whereas PCIE 8-pin power connectors have 3 +12V and 3 GND, so it seems reasonable to me that you might have one or two unused pins at the PSU end. Unfortunately without any details as to which pins are unused on your old cable it's not possible to say whether the connections will be the same. As there are four pins for each of +12V and GND but only 3 +12Vs are required, it's quite possible that both cables are fine, they just have different "spare" pins.

    If you have a multimeter then you could check the cables (not the PSU!) to see which pins at the PSU end are connected to which pins at the GPU end and satisfy yourself that they are okay.

    Disclaimer: I am not an electrical engineer and if your cable isn't wired up properly, it could damage or destroy your PSU and/or GPU.

    Edit: ooh, synchronised post with @Big Elf , but his google-fu is better than mine! :D

    Edit2: changed to say that only 3 of the +12Vs are required at the GPU end - there are 5 GNDs (2 of which are GND/sense).
     
  6. malccy72

    malccy72 Member

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    hi, am really sorry - have not been very helpful. Hopefully this post can clarify things a bit better.

    PSU is a Corsair TX750M.

    existingpsucable.jpg This is picture of the pin layout (going into the psu) of existing pcie power cable. Goes to 2 x 4+2 pcie power


    psucablenew.jpg This is the new pcie power cable i've bought and received. As can see the blank pin is at the bottom right with this cable which is different to my existing pcie power cables layout.

    Hope this help.

    Thanks again
     
  7. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    Compare the image in the link I posted for the 'view towards the power supply' to your cables. The pins missing from each cable correspond to the 12V cable so you're good to go.

    Even if you were showing the wrong end of the cable i.e. from the device end; because of the pinouts for the 12 V supply only populating the last 3 pins on the bottom row you'd still be good to go.

    You're quite right to check the pinouts if you're unsure. Better safe than damage a component.

    I don't know if it's still the case but the Corsair forum used to be excellent for this kind of advice.
     
  8. malccy72

    malccy72 Member

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    On both pictures i'm showing the connections that go into the psu.

    Believe it's a type 4 cable and unsure whether I should have bought a type 3 though some sites i've read it makes no difference. What makes me nervous is i've seen two other pictures on sales of pcie cables and they both show the layout of the new cable that i've bought rather than the existing one that came with the psu. Why are they different. I'm still unsure whether to use the cable i've bought.
     
  9. Big Elf

    Big Elf Oh no! Not another f----ing elf!

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    The main reason thy are different is down to the person assembling the cables who do it their own way within the specs. I have 2 identical SeaSonic PSUs given to me by SeaSonic that have different pinouts on some of the cables.

    If you have a multi-meter I can either try and find the guide I wrote on Overclock.net a few years ago or try an recreate it from memory. You'd need to plug the 2 cables in, disconnect all the other cables from the system and 'jump' the PSU to start it but you can then check voltages/ground connections to confirm.

    Edit: Not exactly a guide but Post #83 details how to interpret the results. I used to do a fair bit of sleeving work on PSUs, including making replacement cable sets a few years ago but it's now a while since I did it on a regular basis.
     
    Last edited: 10 May 2020
  10. malccy72

    malccy72 Member

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    Thank you Big Elf for replying and helping. I don't have a multi meter and am not skilled in that area to know what i'd be doing. I was just after an answer as to whether this new cable is safe to use and wondering why the cable that came with the psu has a different pin layout that the one I have purchased.
     

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