I suspect age of the PS Unit.

Also you may want to run some tests on the components too, I have had experience of parts getting zapped by failing/faulty PS Units and other times it has not.

It's basically a crap shoot, you just never know if any other component took a hit as well.

The electrical resistance of a connector should be as close to zero ohms as possible in order to do transfer as much energy as possible to the load. When the connection loosens up or corrodes with age or abuse its resistance increases, creating a voltage drop in the connector itself, such voltage drop draws some current which produces heat. As the connection heats up and expands it loosens up even more, resistance goes up, current goes up thus producing more heat, if the current is high enough the connector will visibly burn or melt. The low voltage lines on a PC can carry enough current for this to happen.

In your case it was probably a flaky ATX connector on the PSU since you replaced the whole PSU and everything works fine. Just make sure that the pins on the ATX connector on the motherboard are clean and shiny, and that the connector fits snugly. And of course refrain from using cheap power supplies. 😵

I'd give that system a minimum of 400W myself, just to give some headroom for the 7900GT at stock -- 350W is pushing it on the line. And when it comes to PSU, I'll only take two brands as of now: Seasonic and Corsair. Especially with some Corsair models, you gotta love the 7-year replace warranty. I know there are other good manufacturers, but I'll trust any model these two have in their lineup.

Btw, OT, are you using the CT-479 socket converter? I have a dead Fujitsu Tablet PC (burnt onboard VGA) with a Pentium M, now thinking maybe it can get some use on my socket 478/865PE mobo (Chaintech). Will it need a BIOS update or something? Or does it only work on ASUS motherboards?

edit: Nevermind, looks like it's only supported on some ASUS models... 😒

found some recommendation for the 7900GT (Gainward): 400W with 12V+ rail greater than 22A.

Like 133Mhz said the connector got corroded or was not so tight fit with vibration causes tiny sparks and in return causes heat.
The heat causes black connector molten, stiffy cable, board brown by heat for long time.
Youre lucky the pc did not catch fire.
There are connectors from psu's that have gold contacts for better conduction.
Usually the 4p molex connectors for hdd etc are also a bad fit which is some cause for hdd's to catch bad sectors and dipping out on power for 1sec in use.

With a small screwdriver you can bend the round holed connectors to a oval which has a tighter fit and preventing such thing you experienced.
As for the fortron it would be able to power a Quadcore, Bad connection was the devil. fortron is a cheap but reliable psu in my oppinion, only not so power efficient, no 85% rates etc.

Use small sandpaper to grind up the contacts and clean up with ipa.
For the fortron contacts fill with ipa and scratch out with turning inside out a small screwdriver and make oval tight connector.
PSU is ok, nothing wrong, if the caps would be bad probably you would have seen BSOD's.
And maybe the only thing still using the 3.3v line is the memory power supply chopping it up to 2,55v.

- Just wanted to thank you all for the input. 😀
A little late, I know, but forgotten to check in on this topic for a while now.

Anyways, seems like we'll go for bad connection being the most likely culprit.
But I don't dare use that PSU anymore, burnt cables/contact and all, and me having opened it - so it's being properly recycled...

400w... well I knew I was kinda pushing it with the (supposedly) 350w.
But as it was working fine for so many years, I did not think it would be a problem.

JaNoZ wrote:

With a small screwdriver you can bend the round holed connectors to a oval which has a tighter fit and preventing such thing you experienced.

Use small sandpaper to grind up the contacts and clean up with ipa.
For the fortron contacts fill with ipa and scratch out with turning inside out a small screwdriver and make oval tight connector.

What does 'grind up' mean, or why ?
(and what is 'ipa' ?? 😕 )

The mobo ATX connector looks(naked eye) undamaged(?) though, still clean with no burns or residue(?) there. Nor on the PCB.
The PSU connector is another matter... 😜

PS: looking to buy a 'modern' PSU, but seems like the chosen Corsair AX model have (random) 'coil whine' issues... hmm...

grind up = rub down , make shiny
ipa = iso propyl alcohol

bestemor wrote:

400w... well I knew I was kinda pushing it with the (supposedly) 350w.
But as it was working fine for so many years, I did not think it would be a problem.

Looking back, for your load (Pentium M under 30W and 7900 GT at ~82W with only a few peripherals), your 350W FSP is more than capable. The (supposedly) cheap connector is just unfortunate.

PS: looking to buy a 'modern' PSU, but seems like the chosen Corsair AX model have (random) 'coil whine' issues... hmm...

It'd much better if you could buy local at a store that gives you hassle-free 1-to-1 replace rather than buy online. I read so many DOA/RMA reports even on top models from top brands which is surprising.

Here you go

http://www.guru3d.com/articles_pages/geforce_ … 7900_gtx,4.html

"For a GeForce 7900 GT or GTX graphics card, NVIDIA recommends a 350-400 watt power supply with 22-26 ampere on the 12 volts rails."

So your 350W PSU was right on the edge of being acceptable to power a 7900GT when it was new. After several years of use it probably was no longer capable of delivering what the 7900GT needed and started to burn up.

sliderider wrote:

"For a GeForce 7900 GT or GTX graphics card, NVIDIA recommends a 350-400 watt power supply with 22-26 ampere on the 12 volts rails."

So your 350W PSU was right on the edge of being acceptable to power a 7900GT when it was new. After several years of use it probably was no longer capable of delivering what the 7900GT needed and started to burn up.

If you calculate 22-26A on the 12V gives 264W~312W, that's a huge safety margin when applied to OP's Pentium M rig (<112W for CPU+AGP, though not including the rest but still...). Also 7900 GTX's TDP is rated at 120W, ~38W more than the GT, hence the range recommended above.

After re-reading 133MHz's post above I think that's the more likely explanation. Of course one can say it's "premature aging" caused by bad connector.