Asus motherboard short. - Page 1
Forum section: electronics / beginners

author: SenSeS
author_rank: Contributor
timestamp: December 21, 2015, 06:25:20 pm
content: So there is a short when I plug in my power plug to my laptop. I first noticed this because the LED on my power adapter goes dim when I plug it in and it doesn't charge. I then took voltage meter and indeed noticed that there is no voltage drop over the + and GND pins of the female dc barrel jack on my motherboard. I then desoldered the barrel jack because I thought that might be the issue like in this video. Unfortunately, the GND and VCC pins are still shorted, I detect this by using a continuity meter. Are there any components that commonly fail to short on this motherboard that I can try to check? If you need any further details because of poor question formulation, please let me know, I'm a noob when it comes to motherboard troubleshooting! Thanks!Top side, In the top left you can see where I took out the DC barrel jackBottom side, top right you can see where I took out barrel jack.Barrel jack I took out

author: kfitch42
author_rank: Frequent Contributor
timestamp: December 21, 2015, 06:49:11 pm
content: CAVEAT: I am mostly a newb as well, and most of my knowledge comes from watching Dave's various repair videos (watching a few of them might help).I can't say anything specifically about your motherboard. But as a general rule one of the first places to look is capacitors. Electrolytic capacitors are the worst offenders, but they tend to fail open more than short. Next is tantalum. These do tend to fail short. After that comes things like diode bridges, which might not be so relevant since this appears to be a laptop motherboard with a DC input instead of AC.That all being said, I don't see many electrolytics in the pic you posted. As for tantalums, I don't immediately see any (the tend to be yellow/orange), but as a newb looking at a relatively low res pic, I might be missing them.I would start looking carefully in the area near the DC jack for anything that looks damaged (e.g. bulging, burnt, melted, discolored...) If you see anything post a pic, and we can take it from there.P.S. Just to clarify you might want to double check that you checked the right two pins for continuity.

author: wraper
author_rank: Unknown
timestamp: December 21, 2015, 06:49:42 pm
content: Probably shorted TVS protection diode connected from power to GND.

author: sparx
author_rank: Contributor
timestamp: December 21, 2015, 08:04:26 pm
content: Feel the board, if you've got 19V (at a potential of 3A~) going short then I'd guess it's likely something is getting very warm.

author: SenSeS
author_rank: Contributor
timestamp: December 21, 2015, 08:53:32 pm
content: Hi Guys, Thanks for the replies.I believe I found the component, looks like an 0804 ceramic cap that was sitting next to the DC barrel jack. I took it off and when plugging power cable in I'm not getting a short anymore, so so far so good. Only issue now is I have no idea what kind of cap this is. Looks like a ceramic. Is it possible to measure the capacitance if it failed to short? (I'd have to borrow a multimeter that can measure capacitance, otherwise i would of just tried) If not, what should I do in terms of cap value? just put a 10uF or leave it off =)?

author: ciccio
author_rank: Frequent Contributor
timestamp: December 21, 2015, 08:59:00 pm
content: Try a 100 nF to 220 nF, 25 V rating. You will do no damages.Maybe the board will work with no problems even without the capacitor...Best regards

author: SenSeS
author_rank: Contributor
timestamp: December 21, 2015, 09:08:47 pm
content: Quote from: ciccio on December 21, 2015, 08:59:00 pmDoesn't that seem a little low for an 0804? I'd expect to see that in 0603 or less.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: December 21, 2015, 09:11:38 pm
content: Does it work without the cap?

author: cpt.charlie
author_rank: Contributor
timestamp: December 21, 2015, 11:41:24 pm
content: Sometimes some of the input capacitors go shorted, just remove it, unless you have the schematic you won't find the value, but don't worry, the computer will work just fine.

author: jmegar324
author_rank: Contributor
timestamp: December 22, 2015, 08:48:13 am
content: can you take higher res pics?