My Motherboard Released the Magic Blue Smoke!!! Update: It Lives!!! - Page 1
Forum section: electronics / repair

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 12:34:30 am
content: Hello everyone. My gaming computer released the magic blue smoke today when I plugged in a faulty DVI cable into the onboard graphics. This cable had given me troubles before when I used it on my normal graphics cards, but the cards just simply shut off instead of exploding things. I decided to mark the cable as defective using the Photonicinduction method that way I wouldnt mix it up with my other 50 spare cables.Anyway, when the cable was plugged in, after about 10 seconds I smelled the smell that we are all familiar with. However, the PC kept going. My eyefinity monitors weren't disturbed, and the audio I was playing continued to play. I shut the machine down immediately and unplugged the cable once I smelled smoke.Is this machine still safe to operate? Or should I desolder the blown component? I have had SMD soldering experience. If I desolder anything, what should replace it? The failed component appears to be D8, a diode? I have some low-tech marco photos of the only visibly failed part as well as the annihilated cable in a .zip file, and they can be found full size here:https://drive.google.com/file/d/0B-LjUeh-cirIeVJTbEYwa1pUMnc/view?usp=sharingMotherboard is an Asrock Z77 Extreme4 if anyone has the same board.Thanks!!

author: romantronixlab
author_rank: Regular Contributor
timestamp: April 26, 2015, 01:25:01 am
content: Picture would be best to attached to the post for later reference. Was not able to open zip.The diode most times is not just what could be gone, check also for regulators and resistors near the dead Diode. and component.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 01:26:12 am
content: Sorry about the .zip, I did not want the photos compressed.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 04:21:26 am
content: Images can be found as direct uploads here:Sorry, the forum wants 1mb max per file, and 2mb total. My photos are about 2.5mb each.

author: Grapsus
author_rank: Regular Contributor
timestamp: April 26, 2015, 09:18:35 am
content: You can fit a lot of pictures in 2 MB, the trick is to crop, resize and use 80 as JPEG compression factor, not 95.Did you test the diode with a multimeter ? Is it internally shorted or open ?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 12:44:50 pm
content: I have not. A bit later today I will remove the board and get out my multicore desoldering braid and electrolube flux and removs the part. It must not be critical considering that it kept running...

author: JBaughb
author_rank: Regular Contributor
timestamp: April 26, 2015, 12:56:46 pm
content: Quote from: iamdarkyoshi on April 26, 2015, 12:44:50 pmIm not sure if thats the correct way of looking at it...

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 12:59:40 pm
content: Quote from: JBaughb on April 26, 2015, 12:56:46 pmYa probably not... I do think that the onboard graphics are nonfunctional now because after the smokd it played the "hardware unplug" sound.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 06:55:52 pm
content: Now I think that the component was an "LNW 24" as there are many elsewhere, but the board designators are inconsistent. See photos

author: SL4P
author_rank: Super Contributor
timestamp: April 26, 2015, 09:20:59 pm
content: D8 is unlikely to be the same component as Q anything...Look for another D in the same package - and youMAYbe half way there - but not for sure.Ideally find someone with another board and check a known uncooked part

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 26, 2015, 09:40:01 pm
content: Quote from: SL4P on April 26, 2015, 09:20:59 pmI have found someone on the linustechtip forums. Awaiting response.

author: Rasz
author_rank: Super Contributor
timestamp: April 27, 2015, 07:50:48 am
content: why not use continuity tester and check pins of this component against dvi pins? it looks like a clamping diode, maybe on +5v DVI provides?

author: rob77
author_rank: Super Contributor
timestamp: April 27, 2015, 08:16:22 am
content: Quote from: Rasz on April 27, 2015, 07:50:48 am+1actually it looks like a dual diode in sot23 - and apparently only one side is blown.

author: bktemp
author_rank: Super Contributor
timestamp: April 27, 2015, 08:52:54 am
content: LNW = 2N7002 = N-channel mosfetThis matches the Qxx on the board.

author: macboy
author_rank: Super Contributor
timestamp: April 29, 2015, 02:53:27 pm
content: Quote from: iamdarkyoshi on April 26, 2015, 06:55:52 pmHighly unlikely. "Q" indicates a transistor, in this case a MOSFET. "D" indicates a diode. Either can be in a SOT package.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 29, 2015, 03:10:05 pm
content: Quote from: macboy on April 29, 2015, 02:53:27 pmWhich is what made me skeptical. However, the blown part has a clearly visible L, a somewhat visible N, and possibly a fainly visible W? Also, the board's designators are hard to understand. I cant find anything else in the area that could be a diode though. I am in touch with another owner of the same board, and he is going to get me some photos of his.

author: senso
author_rank: Frequent Contributor
timestamp: April 29, 2015, 10:38:03 pm
content: I can tell you the obvious, PQ is Power Transistor/Mosfet, SQ is Signal Transistor/Mosfet.

author: macboy
author_rank: Super Contributor
timestamp: April 30, 2015, 01:38:06 pm
content: Quote from: iamdarkyoshi on April 29, 2015, 03:10:05 pmThat is the best course of action. No guessing.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 30, 2015, 03:18:30 pm
content: Quote from: macboy on April 30, 2015, 01:38:06 pmOr perhaps sparkfun's "magic blue smoke refil kit"

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: May 04, 2015, 03:28:10 am
content: Alright everyone, got some details from the Asrock forums:parsec wrote:"OMGosh, a photo of that part would require a macro lens on a digital SLR camera.Using a high power magnifying glass and two lights I was able to see the markings, clearly after several attempts. It is:LNW 22The 22 is rotated 90 degrees counter clockwise relative to the LNW. This part is labeled D8 on the board, so apparently is a diode.You'll need better luck than I had reading that part, trying to replace it IMO. You must have experience with surface mount devices as well as the tools to work with them.Good luck with this project!"So that is what we have for information. Any chance I would find this same part on another older scrap motherboard? How does one read the marking on these parts?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: May 07, 2015, 11:18:11 pm
content: It lives!! Both the onboard and the crossfired graphics cards work! I used a mosfet that had similar specs stolen from a scrap Pentium 4 mobo , and aside from a different number, it looks new. Thanks everyone. Now to get back to CAD work. And games

author: gildasd
author_rank: Frequent Contributor
timestamp: May 08, 2015, 08:38:34 am
content: Quote from: iamdarkyoshi on May 07, 2015, 11:18:11 pmCool! Job well done!

author: jaycee
author_rank: Regular Contributor
timestamp: May 10, 2015, 05:03:42 pm
content: If this was on the DVI output pins, it was likely a dual diode wired up as a "catch" diode.. one to +v and one to ground. It's likely your faulty cable caused a short to a higher supply. You can also get this happening if you have no power ground and a chassis is floating at half mains.