Custom made molex cable causing PSU freeze?

ozzaman · 27 May 2018 at 02:36

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.

Habakkuk · 27 May 2018 at 04:47

What AWG size wire did you use?

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

ozzaman · 27 May 2018 at 13:05

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

K Olley · 27 May 2018 at 17:05

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.

EsaT · 27 May 2018 at 18:35

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.

ozzaman · 27 May 2018 at 19:24

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.

Habakkuk · 27 May 2018 at 21:31

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.

LuckyBenski · 8 Jun 2018 at 00:56

Habakkuk said:
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.

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