Something broke, burning electronics smell - help me diagnose.

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Rizen

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So we were working on getting my friend's PC stable at 3.8 GHz, which is using a Gigabyte X58-UD3-R, i7 920, 6GB RAM, a Corsair 750w PSU and a Thermalright cooler. Everything was fine, we were about 15 minutes into LinX testing, processor was running at 71C. I went to open Chrome to show him a website, and the PC shut off. 2-3 seconds later, the smell of burning electronics filled the room.

We don't have an extra X58 system here to test, so we are trying to figure out what is wrong.

I don't believe it was the power supply - his system doesn't draw near 750w. There was no pop or noise when it shut off, it just powered down. But we can't narrow down the burning smell to a particular component. I'm thinking we burnt something on the board, or possibly the i7, but I have subjected my i7s to a lot more abuse than he has and no problems yet.

Suggestions? We tore it down but nothing is obviously broken.
 
Hm.. Get a magnify glass and check for burnt MOSFETs, capacitors, socket pins, or CPU die.
 
Probably burnt a MOSFET. Most likely you won't see it til you take off one of the heatsinks.
 
I'm willing to bet it was the PSU.

I blew a Corsair 620HX while overclocking when it was well under the rated output. I considered it a defective unit as the replacement handled the same loads perfectly fine.
 
I am much more willing to bet on the motherboard. Motherboards have a higher tendency to fail than good quality power supplies.

Take off the motherboard heatsinks and see if there's any burnt markings on them. Most likely it's a burnt MOSFET.

Have you tried to power on the system? Usually, if its a burnt MOSFET (although it could also be the CPU), everything would start up, but the system won't post. I doubt it's the CPU though, you weren't anywhere near the thermal limits of your CPU.
 
I am inclined to agree witht the MOSFET consensus. From my experience in my electrical engineering courses MOSFET gates tend to be very sensitive. All it takes is an over voltage to burn a FET gate. Standard BJT's are current driven while FET's are votage driven. Usually 6-13 volts can burn a FET gate depending on the type, while BJT's can take up to maybe 50 volts on the base as long as its current and voltage ratings are not exceeded, or its power rating. I have burned 160 watt rated IGBT's (FET gated BJT) pushing only 20 watts through them, but a spike was appearing on the gate and essentially welding the gate near fully conducting. It was not cool reading .5 ohms on the gate of them when its supposed to be high impedance in the mega-ohm range. One million ohms vs. half an ohm also ment that a very large current got fed back though my gate drive circuitry subsequently destroying that as well.

Also, being a scientist at heart I would still check everything, even the power supply. Try to get as much information as possible, and try to use some scientific observation eliminating one component at a time until you find the bad one (or unfortunately as many times in electronics there could be MANY dead components).
 
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Thanks for the advice guys and good call on the MOSFETs. I told my friend to check the MOSFETs, so he pulled off the heatsinks this morning. Two MOSFETs were burnt out. He replaced the board and is back up and running. Strange that we burnt the two MOSFETs only running 3.8GHz, at reasonable temps and voltages. But oh well!
 
Good to hear that he is up and running already. All electronic components have tolerances. He probably just got a board with a few out of spec components that would have gone bad over time, better to find out now while overclocking than months or years later having it fail for no apparent reason.
 
MSI boards tend to have a problem with cheap mosfets. Just look on the AMD processors forum and check out how many MSI boards died with x6 processors. And compare that to the number of Asus and Gigabyte failures. Probably never going to buy MSI boards again, at least in the near future, even though they were quick in replacing them (in my experience). I myself have experienced 2 MSI board failures with reasonable temps and voltages.
 
That will definitely make me not want to buy MSI motherboards. Thats one of the crappy things about buying hardware, you dont really know what you are getting until you have it and examine the components. One good thing though is that you can look up the data sheets for components and find out their electrical characteristics to give you an idea of how they will perform.
 
He was using a Gigabyte board, not an MSI board. I have had a great experience with my MSI Xpower board, running 4.4GHz now on water.

He replaced the Gigabyte with an EVGA X58 SLI-3.
 
Hardware is not perfect, its bound to happen even on the best boards. I myself have a Gigabyte board, and have not had any problems. These things happen.
 
Untitledone said:
Hardware is not perfect, its bound to happen even on the best boards. I myself have a Gigabyte board, and have not had any problems. These things happen.
Click to expand...
Agreed. I wouldn't hesitate to buy a Gigabyte board, even after this experience. No manufacturer has a 0% failure rate.
 
Ah, oops. I thought that was an MSI board... might've been because I was looking at your signature.

Yes, I understand random hardware failure. But for me, I am avoiding MSI AMD boards simply because they don't seem to be able to handle Phenom II x6 processors (hence the jump to Gigabyte then Asus). Even the 890FXA-GD70 had failures (as one member here experienced, rather catastrophically).
 
MOSFET and or a choke coil. Happens when you're stress-testing.

Oops... should have read the entire thread before posting.
 
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