Sporadic shutdown adventure — finale

It’s been a while since I’ve written about this issue. Folks might have concluded that re-imaging (reinstalling the OS) my machine fixed the problem.

Well, it didn’t.

Things worked for about 4-5 days, or so I thought. Then suddenly one morning while doing backups (from the local hard disk to a USB-connected hard disk), the machine sporadically shut off and stayed off. I had no 3D applications/games running, so this worried me even more — plus the machine didn’t power back on. Manually powering the system on worked fine, where it came back up and remained up for about 5-10 minutes more before losing power (but this time, starting back up on its own).

At this point I knew the issue was either the motherboard or the PSU. It had to be. I disassembled my system and began inspecting all of the components to see if anything stood out. All the PCBs looked fine from what I could tell, nothing looked amiss or awry.

That is, until I found this…

What you see here is the motherboard-facing connector of a 24-pin ATX power extension cable, used between my Antec TP-650 (TruePower New) PSU and my Asus P5Q SE. Why? Because I use an Antec P180 case. Extension cables are needed for both the 24-pin ATX and 4-pin 12V CPU power connectors. (Note: still to this day it amazes me that Antec PSUs aren’t fully compatible, cable-length-wise, with their own cases/enclosures!). The extension cable cost about US$10 and has been in use for 4-5 years.

In case you can’t tell: from the photo one of the pins is about 3/4ths gone (especially visible in the 3rd photo), while the other is intact but not looking good. I then found myself wondering what the 2 pins in question were for. Reading the official ATX 2.2 specification answered my question:

So the pins in question are two (2) +12V lines. It’s impossible for me to tell what devices on the motherboard use said pins, but it doesn’t take a genius to know that the effect this can have on a system is extremely bad. Admittedly the PC BIOS does monitor +12V (via a Nuvoton/Winbond W83667HG chip), however I never witnessed any oddities there.

I inspected the Asus P5Q SE motherboard: the ATX power connector on the board showed no discolouration, however both +12V pins were extremely tarnished (a dull, dark grey rather than silver).

I pondered whether the issue was caused by the PSU or caused by an issue on the motherboard. I still don’t know which could have truly caused this problem. Gut feeling says the PSU, but as I said, it’s very difficult to tell. Do I deem the motherboard reliable? No. Do I deem the PSU reliable? No.

I’d like to point out that had the 24-pin Molex connector been of black plastic rather than white, I wouldn’t have found this problem. All these new PSUs come with black plastic connectors rather than white, for the stupid reason that it’s more aesthetically pleasing. Seriously, how much time do you spend looking at your motherboard? PSU manufacturers should really use white connectors on everything solely for this exact reason. Otherwise, you end up having to destroy the connector anyway.

Lots of other people have had the same experience I have, though with different PSU brands and different motherboards. Some of my favourites:

Replacement parts are on their way. Too bad it’s so hard to find Socket 775 parts these days; I’m not jumping on the Socket 1366/1155/1156 bandwagon with Intel soon to be releasing their LGA 2011 (Socket R) stuff.