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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-03-2020, 04:36 PM
Re: Lenovo laptop burned/shorted power rail repair

Yeah I've given up at this point haha, I removed all the mosfets and theres still a short on the pad itself which then shows up on the caps above the gpu, so it must be fried or something

Most of those mosfets were destroyed too when i tested them off the board with the meter, I'm going to take it into a local repair shop to see what they think because its very difficult and expensive to buy the individual replacements

Oh well xD

Edit: Im just glad I managed to fix the big explosion on the...

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Last edited by stuntR; 07-03-2020, 04:37 PM.
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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-03-2020, 07:58 AM
Re: Lenovo laptop burned/shorted power rail repair

It hasnt been attempted before me and those caps were soldered back by me, it looks bad but its not causing a short. I had to put more solder because the pads had been damaged due to the heat from the cap shorting originally.

The problem with the burn hole is fixed now, I'm trying to figure out why i have a line of caps shorted to ground now and why my mosfets are giving out 100V when not turned on

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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-03-2020, 06:08 AM
Re: Lenovo laptop burned/shorted power rail repair

Yeah the source pad of the 3rd mosfet up from the bottom is shorted, which must then be connected to the caps on the GPU power rail which are also shorted on both sides. But nothing on the board is getting hot in that area.

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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-03-2020, 05:57 AM
Re: Lenovo laptop burned/shorted power rail repair

I've checked the power rails, on one side of the charger input mosfet I get the 20v, but on the source of it I still get around 100v, and this is then feeding into the big inductor next to it which is getting warm, but not really hot. Also on this rail after the mosfet I am getting around 10V, so there is a leak somewhere as it should be all at 20V from the charger.

I have also found a large row of caps shorted to ground above the GPU - this could be my partial short on the 20V rail

I have the 5v and...

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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-02-2020, 01:20 PM
Re: Lenovo laptop burned/shorted power rail repair

After plugging in the laptop i get 20V at the drain of the first mosfet (AON 7408) but then about 100V at the source! Surely this isnt right? Also it was slowly getting warm and warming the inductors too (nothing burning hot). Any ideas?

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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-02-2020, 09:11 AM
Re: Lenovo laptop burned/shorted power rail repair

Here's a picture of my handiwork

I soldered the components back on and get around 0.31V in diode mode on the rail...

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Last edited by stuntR; 07-02-2020, 09:14 AM.
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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

07-02-2020, 07:03 AM
Re: Lenovo laptop burned/shorted power rail repair

Ok Ive managed to remove the short! I measure the resistance of the power rail to ground and I get 30k ohms and increasing, and in diode mode i get 0.365V. Is this normal?

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stuntR replied to Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

06-30-2020, 04:12 PM
Re: Lenovo laptop burned/shorted power rail repair

Will do thanks, its the first time i've had to deal with damage like this and just wanted some input before I go scraping away at that pad xD

do u reckon those small holes by the caps I removed just go straight through to the other side of the board where the burn is? Hopefully they didnt put any other tracks in between or around that high voltage line?

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stuntR started a topic Lenovo laptop burned/shorted power rail repair

in Troubleshooting Laptops, Tablets, and Mobile Devices

06-30-2020, 11:41 AM
Lenovo laptop burned/shorted power rail repair

First thread here! I've got this Ideapad 720s laptop to fix it has no power or charging so immediately after disassembly I found a cap that looked burned, and on the other side of the board a layer was found in this state.

I believe this is the main power rail as it is on the battery input mosfets. When I plug in the charger and nothing else there is small sparks when it is pressed with a plastic spudger (oh god).

I have taken pictures of the burned area and also removed some capacitors on the reverse to have a better look

Can...

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stuntR replied to New Members - please post your introductions here

in Announcements & Related News

06-29-2020, 05:11 PM
Re: New Members - please post your introductions here

Hi everyone, Cam here checking in!

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