Weird and don't know what's up

[cmdrdredd]

I just had an Ultra Fan controller fail, it actually went up in smoke and caused the CPU fan to stop spinning. After burning up the shielding on some of the cables connected to the fans that is. So I checked each wire and plug running from each fan that was connected to it. Both fine. Removed the fan controller and threw it out. Plugged each fan into a single Molex connector directly from the PSU. Now, here is the strange part. The system gets power and tries to start but won't spin up. As if the PSU is gone. I unplug my CPU fan and bam, it starts up. I shut everything down figuring I have a bad fan. I test the fan alone on a different Molex plug and the entire system boots. So here's the question. Can a single molex plug go bad or short? It was the one hooked up to the fan controller.

What to make of this? System works, and is stable and all voltages read ok but that single molex plug does not allow me to do anything if I have something plugged into it.

My main question is, can a single molex plug go out and be non-functional while everything else be ok?

 

[jonnyGURU]

Absolutely. The TX750 doesn't have "rails", so in the event of a short (like whatever happened in the Fan Controller when it went up in smoke) loads can increase until insulation is melted away and wires cross in only the lead that was plugged into that Fan Controller.

When a PSU has OCP, the PSU trips off once the short creates a load that's greater than a predetermined amount (20A or whatever, depending on the PSU). If a PSU doesn't have this, then everything depends on SCP (short circuit protection) depending on shutting things off before there's a fire, but by this time damage to the unit is already done.

 

[cmdrdredd]

So it's safe to assume that the system will be fine if I avoid using that connector? I wrapped it in electrical tape to remind myself not to use it.

 

[jonnyGURU]

Yeah. Probably fine. But I'd go as far as cutting that lead off as close to the PSU as possible and capping the ends. You don't want whatever short is along that lead somewhere to potentially short again.

 

[cmdrdredd]

Well, here's a weird one. The PSU causes constant reboots. I installed an old Seasonic S12 600watt unit in the system and removed the GTX295 and put an old 9600GT. So now I have no reboot issues however I don't know if it's the PSU or the video card or the motherboard being flaky with that video card all the sudden. I have a whole new can of worms to dig through now.

I am replacing the PSU and motherboard next week to see where I stand.

 

[jonnyGURU]

That's why you don't replace two parts in one shot when troubleshooting. Put either the TX 750 or GTX295 back in and see if it continues to reboot.

 

[cmdrdredd]

That's why you don't replace two parts in one shot when troubleshooting. Put either the TX 750 or GTX295 back in and see if it continues to reboot.

TX750 causes reboots with the 9600GT, that's what I tried first. So it's either the PSU or the motherboard for certain. Replacing both with more up to date and better components should eliminate those from being candidates for issues.