Blew something on board, board still works, but at what cost

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Blew something on board, board still works, but at what cost

Postposted on Fri May 10, 2013 5:33 pm

Long story short, I plugged a 4 pin molex to 4 pin floppy power connector into a fan header on my board. I got my wires all mixed up and made a horrible mistake. I powered on the system, heard a loud pop, and some smoke rolled out. I immediately disconnected the adapter, realized what I had done, panicked, rebooted the system, and...it worked fine. It has been working fine ever since (2-3 days ago). I ran Prime95 for 24 hours to ensure no stability issues, all of my fans work, all of my I/O ports work, and everything else seems to be working fine, with the exception of the fan header that I blew.

So this leads me to the question of what is it that I likely blew? Will it cause issues down the line?

Picture of a burn mark on my case (the fan header (PWR_FAN1) that fried is on the left, burn mark is near top right): http://i.imgur.com/S2EBFbw.jpg

Specs:
* Case: Cooler Master HAF XM
* Motherboard: ASRock x79 Extreme6
* PSU: Corsair Enthusiast Series TX650 V2
* CPU: Intel Core i7-3820
* HSF: Cooler Master Hyper 212 EVO
* GPU: EVGA GeForce GTX 650 Ti BOOST Superclocked
* Memory: 8 GB DDR3 SDRAM @ 1866MHz
* HDD: 2x Seagate Barracuda (SATA II @ 7200 RPM)
* OS: Windows 7 Professional
Last edited by Murderbydeath on Fri May 10, 2013 7:19 pm, edited 1 time in total.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 5:41 pm

Looks like a trace on the underside of the mobo arced to to the case. Pull the mobo and look at the back side.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 5:48 pm

Captain Ned wrote:Looks like a trace on the underside of the mobo arced to to the case. Pull the mobo and look at the back side.


Interesting. Does this mean that a trace is likely burnt and the problem is irreparable? I was thinking that perhaps I simply blew a fuse or a reverse protection diode and it could probably be swapped out...but if I burnt a trace....

I'll take the board out later tonight and take some pictures.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 5:57 pm

If you connected the 4-pin floppy power connector from your power supply to the 4-pin PWM chassis fan controller on your motherboard, you probably fried the fan speed controller chip. For some builds, this may be a non-essential component.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 6:03 pm

JustAnEngineer wrote:If you connected the 4-pin floppy power connector from your power supply to the 4-pin PWM chassis fan controller on your motherboard, you probably fried the fan speed controller chip. For some builds, this may be a non-essential component.


Well, it doesn't appear to be a vital component, since the board is still functioning, but my concern lies with if it will cause future issues. I'm trying to determined what blew, exactly, and then determine if it will cause issues in the future.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 6:08 pm

My guess is that you fried a PCB trace on the underside of the motherboard, and (possibly) also the circuit driving that fan header. If everything else still appears to work, then the rest of the mobo is probably unharmed.

If the blown trace is on the underside (outer layer of the PCB) you might be able to resurrect the fan header by soldering a piece of wire to bridge the blown trace, but you've probably got about 50/50 odds that one of the MOSFETs (the little rectangles with 3 terminals) near that burn mark is fried as well.

Edit: Do you recall how the connector was put on the fan header?
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 6:24 pm

just brew it! wrote:My guess is that you fried a PCB trace on the underside of the motherboard, and (possibly) also the circuit driving that fan header. If everything else still appears to work, then the rest of the mobo is probably unharmed.

If the blown trace is on the underside (outer layer of the PCB) you might be able to resurrect the fan header by soldering a piece of wire to bridge the blown trace, but you've probably got about 50/50 odds that one of the MOSFETs (the little rectangles with 3 terminals) near that burn mark is fried as well.

Edit: Do you recall how the connector was put on the fan header?


It was put on correctly, but it was carrying a 12V current, since it was the molex -> 4 pin connector usually used for floppy drives, but identical to the ones used for fans. This is where my confusion lay when I was plugging things in and I had a major brain fart. So basically I fed a pure 12V current into the circuit that the fan header was on.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 6:27 pm

Floppy connectors have 4 wires, that fan connector has 3. Where was the extra pin of the Molex - above the fan connector or below it? (If you remember...)

Edit: I really wish they would key the connectors such that this kind of mistake is impossible. In similar fashion, you can also plug a PCIe GPU power plug into the motherboard ATX12V power jack. This has the effect of bridging the +12V rail to groound. Not good. (And yes, been there done that... :oops:)
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 6:29 pm

just brew it! wrote:Floppy connectors have 4 wires, that fan connector has 3. Where was the extra pin of the Molex - above the fan connector or below it? (If you remember...)


Above, if memory serves me, since it's keyed that way.

Edit: A picture of the offending adapter: http://i.imgur.com/lRpTUnS.jpg
Edit 2: Another picture for good measure: http://i.imgur.com/qN32Z4P.jpg

Edit 3:
If I'm reading the pinouts correctly, ground was going into ground, ground into +12V, and +12V into tachometric signal (I'm guessing the RPM signal), if that helps.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 9:57 pm

just brew it! wrote:Edit: I really wish they would key the connectors such that this kind of mistake is impossible.


Don't get me started, ATX standards have been around for how long and they still supply you with a bunch of individual PITA pins to plug in Power,HD LED,Reset,Power LED and speaker? $%^$%#! that annoys me, just give me a damn keyed plug already.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 10:54 pm

Mmm, this reminds me of that one time I hooked up a floppy drive but was off by one pin and got a fun surprise when flipping the switch. I still use that PSU, though one of the two floppy plugs and part of the drive melted into goo. Real champ, that power supply. I miss having an A:\ drive and emorage a little bit every time I see a motherboard that won't support a floppy--which is all of them these days--but I don't miss that crappy power plug.
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Re: Blew something on board, board still works, but at what

Postposted on Fri May 10, 2013 10:56 pm

Murderbydeath wrote:If I'm reading the pinouts correctly, ground was going into ground, ground into +12V, and +12V into tachometric signal (I'm guessing the RPM signal), if that helps.

Yup. The trace that blew was almost certainly the one supplying +12V to the header, since it was basically shorted to ground. The tach sensor input may or may not have survived, depending on how it is designed.
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 6:32 am

NovusBogus wrote:I miss having an A:\ drive and emorage a little bit every time I see a motherboard that won't support a floppy.
They all support USB.
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 2:37 pm

I had something come up and I'm out of town for the weekend, but I'll flip the board over, clean off any burns, and take some pictures as soon as I'm back. Might be tonight or tomorrow. Thanks for all the help, guys. Most knowledgeable people I've encountered about this issue (I've posted in like 6 different places).
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 3:10 pm

Murderbydeath wrote:Most knowledgeable people I've encountered about this issue (I've posted in like 6 different places).

Most of us have released the Magic SmokeTM in our past computing endeavors or have been in a position where we had to fix problems caused by "smart users".
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 4:53 pm

This particular "oops!" has come up enough times here in the forums that I asked Dissonance to include a warning about it in the "How to build a PC" guide (which he did).
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 6:33 pm

You do have the brass standoff's on the motherboard tray?? I ask this because the motherboard looks like it is laying right on the motherboard tray in the photo. That could make bad things happen if the motherboard is just screwed to the tray with no standoffs to electrically insulate the back of the board.
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 7:00 pm

vargis14 wrote:You do have the brass standoff's on the motherboard tray?? I ask this because the motherboard looks like it is laying right on the motherboard tray in the photo. That could make bad things happen if the motherboard is just screwed to the tray with no standoffs to electrically insulate the back of the board.

Didn't catch that the first time around assuming that anyone would have the standoffs in place.
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Re: Blew something on board, board still works, but at what

Postposted on Sat May 11, 2013 11:58 pm

vargis14 wrote:You do have the brass standoff's on the motherboard tray?? I ask this because the motherboard looks like it is laying right on the motherboard tray in the photo. That could make bad things happen if the motherboard is just screwed to the tray with no standoffs to electrically insulate the back of the board.

Of course. This isn't the first PC I've built, just the first I've built and done something this silly.
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Re: Blew something on board, board still works, but at what

Postposted on Sun May 12, 2013 6:53 am

I was doubtful that the standoff where missing considering it was a high end build but the picture made it look like the board was touching the MB mounting plate along with the arcing mark on it.
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Re: Blew something on board, board still works, but at what

Postposted on Mon May 13, 2013 8:04 am

I would be assuming that a resistor has popped - that's the obvious result of voltage through a circuit that isn't expecting any - and resistors do go "pop" and release quite a lot of smoke when they are overfed.
Most IC is protected by diodes too - so there's a large chance that everything apart from the fan header itself is still okay.

Obviously assumptions and chance aren't exactly cast-iron answers but I'd just keep on using it for the moment, avoiding that particular fan-header in future.
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Re: Blew something on board, board still works, but at what

Postposted on Mon May 13, 2013 9:25 am

If that header lacks fan speed control (note: some 3-pin headers do have it even though they lack the PWM pin), the +12V pin is probably just wired directly to the +12V power plane (no resistor or other component in between). Most motherboard components also tend to be on the top side of the PCB not the bottom (though exceptions do exist).
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Re: Blew something on board, board still works, but at what

Postposted on Mon May 13, 2013 1:30 pm

I'm thinking it's possible that the Q15 triode (I assume that's a MOSFET -- it IS a SOT-23 transistor, isn't it?) blew, or the D7 diode blew. The D7 diode does look a little jarred in that picture, doesn't it? I'll PROBABLY take those pictures tonight, sorry for all the delays.

I suppose I could easily test if it was the D7 diode, as long as I were careful. Plug a fan in, power on the board, take a wire and jump the diode pin to where the trace goes. But I'm afraid I'd end up shorting something else out, haha.
Last edited by Murderbydeath on Tue May 14, 2013 4:48 pm, edited 2 times in total.
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Re: Blew something on board, board still works, but at what

Postposted on Mon May 13, 2013 1:42 pm

The location of the burn mark seems more consistent with a trace (or component, if there are any there) on the underside of the PCB burning up. If Q15 or D7 was responsible I would expect to see some discoloration of the silkscreened white lettering and graphics on the top side of the PCB.
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Re: Blew something on board, board still works, but at what

Postposted on Tue May 14, 2013 12:34 am

Alright guys, I took some pictures, but...none of them turned out that great. I couldn't get good lighting or the camera to focus, but I want you to know that you were right: it was a burnt trace. The unfortunate thing is that it seems to have burned an adjacent trace along with it. The trace that burned was actually 2 traces that were very close to each other; there's no telling if both were damaged or just one. It looks like both. There was also an adjacent trace that looks like it might have taken some damage. But I can't be sure. The damage is done, though, right? There won't be any issues down the line as a result of this...right?

Pictures (they all suck, sorry; also, you might want to look at the full size pictures, not just the imgur previews): http://imgur.com/QqXtV4Q,JeCzaPC,nmqM3U ... RP,xV9eMr0

There are also a couple of pictures of the back of my CPU mounting plate. Or whatever that thing is. It had some dark marks on it. They look kind of like burns. I find that concerning. But my CPU temps are always fine.

Edit: Wow yeah these pictures are garbage. Basically the trace at the very top of the board is actually 2 small traces. They both looked pretty damaged, as well as probably the trace below them. I'm not sure where any of them go.

Edit 2: if you go to Newegg and look at pictures of the board, you can find a picture of the back of the board that might aid in tracing the traces: http://www.newegg.com/Product/Product.a ... 6813157289

I really apologize for the poor quality of these pictures. I seriously could not get my camera to focus. And I was nervous about having the board in my hands while taking pictures (I really didn't want to take the HSF off)
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Re: Blew something on board, board still works, but at what

Postposted on Wed May 15, 2013 2:16 pm

Anybody out there?
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Re: Blew something on board, board still works, but at what

Postposted on Wed May 15, 2013 2:49 pm

Couldn't tell much from the pics, too blurry. Sorry.
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Re: Blew something on board, board still works, but at what

Postposted on Wed May 15, 2013 4:39 pm

just brew it! wrote:Couldn't tell much from the pics, too blurry. Sorry.


Still, knowing now that it's a trace, you can say if the damage is done or if it will perhaps cause issues that will worsen over time, right? I assume that the damage is done and that no more than what is already damaged will happen, but I could be wrong.
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Re: Blew something on board, board still works, but at what

Postposted on Wed May 15, 2013 7:35 pm

Well, can't say for certain because there could still be latent damage to some other component. But odds are, yeah the damage is done and anything that is still working now will be unaffected in the future.
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Re: Blew something on board, board still works, but at what

Postposted on Wed May 15, 2013 9:50 pm

Battle scars, awesome!

Glad you didn't burn your house down because that's always a real bummer and takes all the fun out of electricity. :o :P
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