Dell xps 13 9343 - dead

[kingdbag]

I have a DELL XPS 13 9343 that I've been using for almost six years now and it finally decided to bite the dust on me yesterday. It does not try to power on at all... I get no light on the power button when pressed. I'm not sure if this is a common failure on these, but can someone tell me what the chip is that is burnt up in my picture? I want to say it was marked T or P 070 or Q70 (on the PCB)? The chip totally burned up so I can't read the markings on the top of it. I don't have a schematic for this as I don't normally repair this kind of stuff... I repair arcade PCBs in my collection that is about it. I do have a hot air rework station so it would be fun to try and replace the chip and see if it fires up. The laptop is in great shape and everything was working well up until I could smell it burning so I'd hate to junk it if it can be saved.

Any pointers would be appreciated, thanks!

[SMDFlea]

Re: Dell xps 13 9343 - dead

The schematic : https://www.badcaps.net/forum/showthread.php?t=65873

Looks like Q70

[kingdbag]

Re: Dell xps 13 9343 - dead

Ok, so I was thinking... well it didn't try and power up yesterday with the power supply not connected. I tried just now unplugged and also plugged in and it fires up, but I can see a faint Dell logo so maybe that chip has something to do with the turning on the LCD backlight?

edit: and someone posted the schematic as I was typing this up... I'll take a look at it, thanks SMDFlea!

[emestee]

Re: Dell xps 13 9343 - dead

https://www.badcaps.net/forum/showthread.php?t=65873

This is the switch that controls the screen's backlight inverter, Q70, AO4407AL.

[emestee]

Re: Dell xps 13 9343 - dead

Ok, so I was thinking... well it didn't try and power up yesterday with the power supply not connected. I tried just now unplugged and also plugged in and it fires up, but I can see a faint Dell logo so maybe that chip has something to do with the turning on the LCD backlight?

edit: and someone posted the schematic as I was typing this up... I'll take a look at it, thanks SMDFlea!

Yes this means your display is okay, it just has no backlight. Remove the transistor and make _sure_ the 19v rail that goes to the matrix isn't shorted.

[kingdbag]

Re: Dell xps 13 9343 - dead

Yes this means your display is okay, it just has no backlight. Remove the transistor and make _sure_ the 19v rail that goes to the matrix isn't shorted.

I'll look at the schematics and see if I can find that rail... I've never tried to troubleshoot something like this so hopefully I can find the rail...

It looks like the part that died is a AO4407AL_SO8 MOSFET from looking at the schematics.

Can I just check the power/ground legs of the MOSFET once I remove it to check for 19v there?

[emestee]

Re: Dell xps 13 9343 - dead

Can I just check the power/ground legs of the MOSFET once I remove it to check for 19v there?

The transistor itself is dead, no two questions about it. You'd want to check its pad for shorts on both source and drain sides, yes. To do that, make sure the matrix is connected. If you connect or disconnect the matrix, make sure the battery is disconnected first. You should see some resistance on this rail.