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Custom made molex cable causing PSU freeze?

Discussion in 'Power Supplies' started by ozzaman, May 27, 2018.

  1. ozzaman

    Gangster

    Joined: Oct 23, 2006

    Posts: 321

    Hi

    I recently made a custom 1.2 metre cable which I am running to a D5 pump and a fan controller which controls 6 fans.

    The strange problem I am having though is that I get random hard freezes when gaming or benchmarking. My pc will freeze, the sound will buzz and then the system needs a hard reset before coming back to life.

    I changed PSU and didnt use the custom molex wire that I had made and the system ran fine.

    I also used my original PSU and was able to use one of the original molex connectors provided and connected the pump and fan controller. This too worked.

    The only variable seems to be the custom made cable which I was using.

    Has anyone else encountered this?

    The PSU i have is a Corsiar HX750i.

    Many thanks.
     
  2. Habakkuk

    Wise Guy

    Joined: Feb 7, 2017

    Posts: 1,004

    What AWG size wire did you use?

    Do you know what the voltage drop & resistance is over the cable?
     
  3. ozzaman

    Gangster

    Joined: Oct 23, 2006

    Posts: 321

    I used 18 AWG wire. I dont have the equipment to test for voltage drop or resistance unfortunately.
     
  4. K Olley

    Associate

    Joined: Dec 17, 2017

    Posts: 9

    Location: Essex

    Many moons ago I watched a motorbike mechanic test some wiring on a bike, although he had some fancy equipment available he was using a battery and a headlight bulb.

    When I asked why he said a fancy meter may show a very low resistance through a poor joint or corroded wire when passing a very low current but on load the same wire or joint will cause problems.

    A similar rig for testing the 12v wiring attached to a PSU could be made up with a car rear fog light bulb (12v 21w) and a bulb holder (breakers).

    Have made up similar rigs as and when needed.
     
  5. EsaT

    Mobster

    Joined: Jun 6, 2008

    Posts: 4,282

    Location: Finland

    Unless voltage drops too much for pump to run etc don't see how additional resistance would cause such problems.
    Though if devices powered by that cable communicate with rest of PC voltage drop (and rise of ground wire voltage) could cause problems in that.
    And longer cabling is also obviously longer antenna for EMI which might get from that to some sensitive component.
     
  6. ozzaman

    Gangster

    Joined: Oct 23, 2006

    Posts: 321

    The actual pump and fans run fine with the longer cable.

    But I have now been able to run the system for a couple of hours with the original Corsair Molex cable and there haven't been any crashes. Not entirely sure what is causing the PSU to freeze, but the longer cable I have made does seem to be doing something weird.
     
  7. Habakkuk

    Wise Guy

    Joined: Feb 7, 2017

    Posts: 1,004

    18 AWG is the usual standard - I can't see it heating up significantly over 1.2m to increase the resistance.

    I missed the 'the sound will buzz' - this is generally a grounding problem IME.
     
  8. LuckyBenski

    Wise Guy

    Joined: Dec 28, 2017

    Posts: 1,357

    Location: London

    Unless it's a buzz from the audio buffer looping, more like grinding than hum.