New motherboard. Saw flash, heard pop, saw smoke

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Mighty

Mighty

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Jan 22, 2010
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Was having issues with my previous machine, and decided to upgrade. Got a new motherboard, CPU,RAM and graphics card.

I've built a coupla dozen systems over the years, so I am experienced.

Everything went in fairly easily. Easily enough that when I went to move it into the office, I went ahead and put the cover on it, first. This case has a window in the side, which I never really wanted, but turned out to provide extra information, for this incident.

When I hit the power button, I immediately heard a pop and saw a flash from inside the case. A second or two later, I saw smoke coming out of the top of the case (apparently not the Magic Smoke.) It lasted for a second or so. If any smoke went out the back, I didn't notice it.

Since I wasn't expecting this, I wasn't watching for it. So I am not certain where the flash happened. My impression is that it was near the top of the motherboard/case.

I immediately moved to turn the power off. Of course, with today's machines, that means holding the power button for five seconds. It was during that time that I saw the smoke. Before it finished powering off, I saw that it was continuing to boot.

I took the cover off and took a look. I expected to see a popped capacitor and/or a scorch mark on the motherboard. I did not see anything like that. It was all clean.

I decided to take a chance. I powered it back up, and it booted. I made it into the BIOS setup and chose a boot drive. It made it into Windows, albeit, my user account is corrupt in some way. I'm going to have to reinstall Windows.

Anyway, as far as I can see, it appears to work.

But, since it's brand new, I decided to go ahead and take a closer look. I'd rather replace it now, rather than have problems show up a few weeks or months from now.

I went ahead and removed it completely from the case. I have good light, and I looked it over pretty carefully. I've scanned all of the caps. I do not see any out of place. No scorch marks on either side of the board. There are a couple of heat sinks attached to the motherboard that make it difficult to see some of the caps. What I can see looks good. I took a close look at the power connectors. Nothing melted or scorched.

When I described this to my father, an electrical engineer, his initial reaction was that that sort of behavior is usually the power supply. I would consider that. Except, the power supply on this case is at the bottom of the case. And, it has its own exhaust fan. I can't picture how the smoke would have stayed inside the case, and made it up to the top of the case that quickly. Especially, to be thick enough to see out the top without seeing smoke pouring out the back.

I wondered about the new graphics card. It's so covered in heat sink that I con only see a few of the components, and not much of its board. What I can see looks pristine.

I expect I'll probably return the motherboard for exchange. I sent an email to NewEgg. But, I was wondering if anyone had any other ideas on what it might be and how I would find it.

Motherboard: ASUS ROG Maximus IX Hero Z270
Graphics card: GIGABYTE AORUS GeForce GTX 1080 Ti
Power supply: Thermaltake TP-850 80 PLUS Bronze (about one year old)

I can list more components, if you think they're relevant.

Any suggestions?

Drake Christensen
 
Solution
Mighty
Followup. Because of that bare wire I found, I'm reasonably confident I've found the source of the flash. I think the smoke might have been the insulation, where that wire went back in. It was a little hard to see clearly, because it was a coupla black wires coming together, that sucked up all the light. But, it looked like it may have been a little less than pristine.

Based on that, I put the thing back together. I ran Prime95 on it for over 30 hours, and it was running when I got back to the office. So, I have some confidence that it's stable.

Now comes the two-day task of reinstalling Windows and getting it all adjusted how I like. *heavy sigh*

Thanks again for the ideas.

Drake
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Flying Head

Flying Head

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A voltage regulator can fail. Evidence would be a small hole and perhaps difficult to see. The downstream circuit would not function, such as sound or USB. A multi-phase regulator for the CPU would have one less phase.
 
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Karadjgne

Karadjgne

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Check the case itself, especially around the area of the upper drives etc where the power leads for hdds, opticals or even intake fans go. It's not uncommon to see a pinched wire there that'll short out, or a wire run through the case holes to the back side pulled too tight when the back side panel is put on.
 
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Mighty

Mighty

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Thanks for the suggestions.

I did pull the motherboard out of the case to look at it more closely, on both sides. No scorch marks on the back side.

I never thought to use my nose. I understand the principle. But, I have learned over the years that my sense of smell is less acute than average. I'll give it a try, though.

Over the life of this machine, I have had occasion to rearrange the wiring on the back side. In some cases there was tension on the cables. In others, they had bunched it up so much that it was difficult to get that side of the case on. (It has foam sound insulation.) I have looked at those cables recently enough to be sure that none are now under tension, and none are frayed where they did and now do go through to the other side of the motherboard. (Aside: I've become a huge fan of twist ties and velcro instead of cable ties. Cable ties make it really inconvenient to rearrange cabling.)

I'm reasonably sure that the power and data cables to the optical, SSD and HDD were not pinched. I paid attention to that. The GPU did come in contact with the HDD case. But, they were offset from each other enough that neither was being twisted. They were just overlapped a little and touching each other. I've since repositioned the HDD so that won't be true next time I put it together.

The case intake fans are in the front, near the bottom. Another instance where the smoke could not have gotten to the top that quickly. I do have two exhaust fans mounted in the top of the case. And, two fans to pass air through the liquid cooling radiator. If those latter were the source, I would expect the smoke to get sucked right out the back. I did look closely at the fans at the top of the case. I can see both sides clearly. I do not see any scorch marks.

As for the voltage regulator idea. As I said, it did successfully boot into Windows. I suspect if the problem were that severe then it would fail long before getting that far.

As I was rearranging some cables, I did spot a possible culprit. Whoever spliced the case speaker wire let a few strands of the bare copper wire dangle outside the heat shrink. About an inch and a half of wire. It could be one of those which touched something. Unfortunately, those cables have been moved around since then, so I'm not sure exactly where they would have touched live components. It's in the crowded general area, about halfway up the case, where the GPU and the HDD came together. Which is just a coupla inches from the main motherboard power connector. And then just general bits along that edge of the motherboard.

I snipped those bare wires off.

That could explain the flash and pop. But, I still wonder about the source of the smoke. It was enough smoke that I sure expected to see evidence at the source.

I didn't look closely at the bottom of the hard drive. I suppose that since the motherboard is currently out, now is the best time to pull that back out and take a look.

Thanks again for the quick suggestions. I really appreciate the ideas.

Drake
 
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Mighty

Mighty

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Jan 22, 2010
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Followup. Because of that bare wire I found, I'm reasonably confident I've found the source of the flash. I think the smoke might have been the insulation, where that wire went back in. It was a little hard to see clearly, because it was a coupla black wires coming together, that sucked up all the light. But, it looked like it may have been a little less than pristine.

Based on that, I put the thing back together. I ran Prime95 on it for over 30 hours, and it was running when I got back to the office. So, I have some confidence that it's stable.

Now comes the two-day task of reinstalling Windows and getting it all adjusted how I like. *heavy sigh*

Thanks again for the ideas.

Drake
 
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