Author Topic: Laptop Asus R511LJ power problem  (Read 1570 times)

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Offline antoinelgTopic starter

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Laptop Asus R511LJ power problem
« on: August 22, 2017, 09:50:09 am »
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/XKyqQF
https://flic.kr/p/XKyiig
I 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 !  :)
 

Offline Toasty

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Re: Laptop Asus R511LJ power problem
« Reply #1 on: August 22, 2017, 02:36:35 pm »
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

veritas odium parit
 

Offline antoinelgTopic starter

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Re: Laptop Asus R511LJ power problem
« Reply #2 on: August 22, 2017, 02:54:40 pm »
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 !
 

Offline Toasty

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Re: Laptop Asus R511LJ power problem
« Reply #3 on: August 22, 2017, 06:41:10 pm »
Excellent!  :D

T

BTW: Keep the heat down to 350-360°C and a good measure of flux.
« Last Edit: August 22, 2017, 06:43:19 pm by Toasty »
veritas odium parit
 

Offline Rasz

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Re: Laptop Asus R511LJ power problem
« Reply #4 on: August 22, 2017, 10:14:24 pm »
7 Ohms on cpu dc/dc is absolutely fine

my 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
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