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View Full Version : Motherboard / PSu problem...



zeradul
02-08-2002, 02:56 PM
A friend came to me with this problem today...

After working fine for 2 months, his computer started pumping out a very strong burnt smell... Nothing software related was having problems, the computer was running fine, but we shut it off none the less and opened it up... We discovered all 4 of the red wires had began to burn causing the red wire insulation to bubble near (and inside the large molex connection) that connects the power supply to the motherboard. It has seemed to fuse the two together making it impossible to disconnect the power supply from the mobo. Just the red wires were affected...

We built his computer about 2 months ago (early december), and it had worked fine ever since. The motherboard is an Epox 8KHA, with a 1.4 T-Bird, 256 Megs of Micron DDR.... Matrox G450 (dual video out) Netgear NIC, and a Generic Modem. None of the parts seem to be harmed, like I said everything was working fine, even as these wires were being burnt.

I have been using google in an attempt to find a schematic of the motherboard connection, to find out what the red wires do, but I have had no luck.

Everything in the computer appears perfectly normal, except for the burnt insulation on the 4 red wires (burning only occured within 1 centimeter of the translucent connection) and clearly burned a dark line down to the motherboard through both halves of the translucent connector....

On the back of the motherboard very faint burn marks can be seen near where the wires come though the mobo and stick slightly out the back.

Anyone know what went wrong? My buddy is ready to buy a new powersupply and mobo, but wouldn't mind a replacement from MWave if it can be determined that it was faulty. The power supply was new, as was everything in the computer, 300 watt, AMD approved.

*shrug*

No lightning strikes, no other wierd stuff, i dunno... We got the stuff from MWave, any suggestions on how to treat a return situation with them would be appreciated...

pretty wierd ehh? Any Ideas?

FrodgE
02-08-2002, 04:30 PM
hehe, maybe you need another fan for the atx connector ?!

This is unlikely to be the problem but if the connector on the supply was a bit dodgy it could have been arcing and getting hot etc. Otherwise the only other thing I can think of it that too much current was being drawn from the supply. That doesn't seem right because the psu should detect this and shut down. Maybe the ATX connector had the pin out wrong ??? That just sounds too stupid to be the cause but once again the psu should detect this and shut down. maybe the case or something was shorting but as I said before shorely the psu would detect this !

I dunno ! Red to my mind generally means a positive voltage rail. If it was and it was having problems the psu should detect too much current and turn off so maybe it isn't. What pin number on the connector is it ?

Anyway there you have it, a useless answer with lots of words !

I'm thinking someone should try answering this ! :crazy:

zeradul
02-08-2002, 05:09 PM
Thanks for your thoughts Frodge...


connector on the supply was a bit dodgy
Nope, it was solidly connected, firmly in place, so snug in fact that with a little bit of heat now i can't get it apart.


Otherwise the only other thing I can think of it that too much current was being drawn from the supply
I really doubt that, It had been running for 2 months with out a problem what so ever, and there really wasn't anything drawing alot of power... just the cards i mentioned, 1 7200 drive, a cd-rom and cd-r, and some fans, but they weren't plugged into the mobo for power...


Maybe the ATX connector had the pin out wrong ???
Like I said it had been running fine for 2 months...


maybe the case or something was shorting
I looked for marks and whatnot and found none, nothing had been added to the computer in the recent past... no changes made recently...


maybe the case or something was shorting
EVERY red wire connecting to the motherboard from the PSu... total of 4... I could look up pin #'s but i'm assuming the color choices are a standard...

Mr. C
02-08-2002, 06:50 PM
Is it possible that perhaps your friend was the victim of a power surge/fluctuation on the outlet the PSU is plugged into?

zeradul
02-08-2002, 08:56 PM
I thought of that too, but we are in the same building, our circuit breakers are in the same box, and nothing happened to his laptop, or any of my computers...

And everything was working fine !!! which really gets me... I'm convinced that if we put it back together and turned it on, everything would work..... well maybe not everything now, heh, something is definatly wrong, but I bet it would boot into windows...

Birdkiller
02-08-2002, 09:01 PM
The read wires are all +5V DC. I agree with Mr. C that its probably a power fluctuation/spike or maybe a short in the PSu due to a critter crawling in there.

zeradul
02-08-2002, 09:04 PM
No chance of any critter walking around in it.. hehe

FrodgE
02-08-2002, 11:23 PM
yeah I know, dodgy thoughts ! The main reason i didn't suggest a surge is that something like that would surely fry something (other than the wires). Regarding the dodgy connector, I wasn't refering to the plastic casing but to the the metal contact inside the plastic. They're often not as good as they should be.

Not that it matters 'cas I'm pretty sure that wouldn't be it. Hmmm, 2nd reply in this post and I still haven't got a clue... why am I bothering !

T-Shirt
02-09-2002, 12:26 AM
Regarding the dodgy connector, I wasn't refering to the plastic casing but to the the metal contact inside the plastic. They're often not as good as they should be.

!

This would be my guess. slightly defective, gets warm, resistance goes up, gets warmer.
other choice would be a motherboard defect, just took a while to fail, but Epox has pretty good QC.
Try another power supply, keep the case open and check the temp. for a while

T-Shirt
02-09-2002, 12:33 AM
also, check for dust , moisture, etc. Unless the power supply had way undersized wiring, melting the insulation implies a serious short. (more than a brief arc "should" do)

Albinus
02-09-2002, 11:44 AM
My view is that the PSU wasn't up to the task of running a 1.4GHz T-Bird. AMD processors, pardon the language, "rape" the 3.3V and 5V rails of a PSU. This is why Intel has invented the ATX 2.03 standard, to let the motherboard transform the 12V rail into the correct CPU core voltage.

Why?

The 12V rail in a PSU is often under-utilised. It powers mechanical things, such as fans, and the motors in Hard Drives and CD/DVD-ROM's. The 5V rail powers electronics such as the motherboard, drive electronics and the CPU. 5V and 3.3V power in an ATX power supply is transformed down to the correct voltage for an AMD 1.4GHz Athlon (1.75V if I remember correctly?) :?:

Intel seized upon the idea of the 12V rail being mainly unused. The largest stress on the 12V rail is when the power button is first pressed, this is when all the fans and Hard Drives spin up. After that, you're lucky if the 12V rail is any more than 50% utilised. So Intel made it possible for the motherboard to use this free 12V capacity, freeing up the 3.3V and 5V rails to run electronics.

This is why a 300W PSU will comfortably power a decked-out 2GHz Pentium 4 drawing over 90W of power under load. A similarly loaded AMD system will need at least 350W, if not 400W to run reliably, despite the lower current draw. When too much current is drawn through a particular rail, it gets hot and melts the insulating material (as what happened here).

So my view is to get a larger PSU - and let's hope that AMD starts adopting the ATX 2.03 standard soon :)

zeradul
02-10-2002, 08:39 AM
I see, that does make alot of sense...

That explains why everything was still working... and would explain why the wires got hot enough to burn the insulation... a surge would be so instantaneous I doubt it would burn anything... and if it did it would burn everything...


So do you guys think that the motherboard is still good?

zeradul
02-10-2002, 12:06 PM
Heh, As you can probably imagine, if there is heat enough to melt and burn the wire insulation, its enough to melt the connector... I really pulled on it, its not going anywhere. Its melted together...

Not much we can do ? Any other ideas would be helpful... heh

I just realized that vbulletin can host images, I will get the pictures my friend took and post them up here for you guys...

Albinus
02-10-2002, 12:15 PM
I feel that the motherboard is still OK..... just if you can pry that sodding ATX connector out somehow :?:

Try a very small flat bladed screwdriver, if that fails then you are up for soldering 20 wires to an ATX extender plug - this will allow you to use the melted plug with another PSU, like such:

Motherboard --- Melted plug --- soldered wires --- ATX extender --- ATX power lead --- ATX power supply

Hope this explains things :confused:

zeradul
02-10-2002, 04:05 PM
I see what you're saying, but that doesn't eliminate the problem... The heat was originating within the plastic plug, most likely where the wire meets the little electical contacts that actually electrically touch the mobo... so I Need to get the old power supply side of the plug out, because if i don't they electrical bottleneck (that caused the heat) is still there, and it will happen again... Hey I bet the cleanest solution would be to remove the ATX plug, and find an old motherboard and un-solder its plug, and then re-solder it in to the injured mobo...

We've pulled and pryed on it hard with no luck... I don't want to crack the mobo... and if I do try to replace the plug, do you think I can solder well enough ? Heh, and will I be able to find a plug that is designed to conduct as much electricity as the T-Brid needs?

Albinus
02-10-2002, 04:23 PM
If a more powerful PSU is used, you won't have any problems with melting :)

So don't worry about that ;)

FrodgE
02-10-2002, 06:32 PM
Unless you're pretty confident about you soldering skills and have all the proper de-soldering tools I wouldn't go near it with a soldering iron !

Unless you're really carefull you'd be extremely likely to cause more damage. Unless the wires in the melted plug have melted together and shorted out then Albinus's idea will be just fine.

I guess you could also cut the plug to bits with a knife and rip bits off / out with a pair of pliers. Use a chainsaw perhaps ? Hmmm, maybe that's going overboard...

zeradul
02-12-2002, 05:42 AM
Here's both sides of the connector...

zeradul
02-12-2002, 05:45 AM
...

Wiggo
02-12-2002, 10:06 AM
Pull out a good knife and see if ya can carefully cut the PSU end away. :smokin:
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