Laptop Asus R511LJ power problem - Page 1
Forum section: electronics / repair

author: antoinelg
author_rank: Newbie
timestamp: August 22, 2017, 09:50:09 am
content: Hi everybody,I have seen this forum helped a lot someone with an Asus laptop and the same problems as I have, so I think I should ask you some help.I've got an Asus laptop R511LJ, my cats made it fall while it was plugged in and the adapter broke in the connector leaving a small metal part stuck in it. After I removed it I tried to power on the laptop and it worked until the battery was fully discharged. Since then, it's not charging anymore, and the power led is off. So I disassembled it and I tried to remove the battery and just plug the adapter (another one, not the one that is broken), no reaction.I thought, maybe with the metal part stuck in the connector some short circuit could have fried a component so I've tested everyone on the motherboard and I think I might have found the area : With a multimeter I get a 7 Ohms resistance between each + and the ground. But it's a large area and I'm not sure a 7 Ohms resistance could be considered as a short circuit.I've got a ~750 mV voltage on the + of the battery connector, i think it should be higher to charge the battery so I ordered a new power IC (BQ24735) but before I replace it I want to be sure the problem doesn't come from a short circuit elsewhere on the motherboard.These are the links to the pictures of my motherboard (top and bottom) with the area plotted in red :https://flic.kr/p/XKyqQFhttps://flic.kr/p/XKyiigI was wondering if you have some advices to find the right (or in this case the wrong) component.The full motherboard replacement part is 599€ so I want to try to repair it, and I think it's a good training !Thank you in advance for your help !

author: Toasty
author_rank: Regular Contributor
timestamp: August 22, 2017, 02:36:35 pm
content: Hello and Welcome!I would not go looking for a problem by randomly probing around with a meter. You could cause other damage.What you marked would not be bad, since the unit was working on battery until it was drained. I think your problem is the power connector itself. It is likely internally damaged. You would not get voltage back there -from- the battery. It has to pass through several components that look for a proper voltage and communication with the charger.I seriously doubt the power IC would be bad. That usually only occurs if you were using a non-Asus charger. Also, replacing that chip requires the proper equipment and knowledge, not just a soldering iron.I would take the whole laptop (not just the motherboard) to a shop that specializes in component repair for laptops. They should be able to diagnose the problem and stand behind their work with a warranty. I would estimate the repair to be in the $100-$150 range, including parts.Just my 2¢T

author: antoinelg
author_rank: Newbie
timestamp: August 22, 2017, 02:54:40 pm
content: Hello and thank you for your reply !I don't think the power connector is internally damaged since I have my 19.2V on the VCC pin of the BQ24735 (that's why I thought the problem was with the IC). You're right I was so desperate that I started to look everywhere for signs of malfunction, and it had nothing to do with the area I plotted, because I think I've just found the guilty ! It's the m0930 mosfet near the power connector (I've just made a bridge and the laptop powered on)I ordered it and will try to change it (I've got a rework station).I hope this will work but thank you again for your reply !

author: Toasty
author_rank: Regular Contributor
timestamp: August 22, 2017, 06:41:10 pm
content: Excellent!TBTW: Keep the heat down to 350-360°C and a good measure of flux.

author: Rasz
author_rank: Super Contributor
timestamp: August 22, 2017, 10:14:24 pm
content: 7 Ohms on cpu dc/dc is absolutely finemy guess would be broken plug shorted in the connector resulting in fried mosfet (if its the one switching between Vbatt and Vsupply)I would still replace power connector, Asus is pretty "famous" for crap charging ports, one google will spit hundreds if not thousands of cases