Dell E6440 shortcircuit

[Andreasbest]

Re: Dell E6440 shortcircuit

Test each mosfet using the resistance mode of your meter and post your updates.

PQ700 and PQ810 Source pins are grounded.
Rest: PQ800, 809, 811, 815 seem fine (with all combinations of G S & D and with GND)

[mon2]

Re: Dell E6440 shortcircuit

1) Lift one side of PL701. Do not power up the logic board.

2) Check if the SOURCE pins of PQ700 & PQ810 are still grounded.

[Andreasbest]

Re: Dell E6440 shortcircuit

1) Lift one side of PL701. Do not power up the logic board.

2) Check if the SOURCE pins of PQ700 & PQ810 are still grounded.

With PL701 lifted the ground shortcitcuit on both mosfet is gone.

[mon2]

Re: Dell E6440 shortcircuit

1) Leave PL701 lifted.

2) Test for shorts on mosfets PQ704 & PQ705.

3) Suspecting that your short is from the attached region of the logic board. Inspect each component.

For the caps, you could quickly remove each and then check if the short is gone or not and then focus on the mosfets.

[Andreasbest]

Re: Dell E6440 shortcircuit

1) Leave PL701 lifted.

2) Test for shorts on mosfets PQ704 & PQ705.

3) Suspecting that your short is from the attached region of the logic board. Inspect each component.

PQ704 & PQ705 Drain all grounded

[mon2]

Re: Dell E6440 shortcircuit

Remove the linked caps as per above schematic to see if the short is removed or not.

If the short is still there AFTER removing the caps, then remove each mosfet.

[Andreasbest]

Re: Dell E6440 shortcircuit

Remove the linked caps as per above schematic to see if the short is removed or not.

If the short is still there AFTER removing the caps, then remove each mosfet.

You mean PC710 713 714 734 ?

[mon2]

Re: Dell E6440 shortcircuit

Yes. If short is still there, remove PQ704 & PQ705 and check again if it is fixed. Do not power up. Only check for shorts.

Have to leave for an hour or so...will check back later. If short is removed, attach the coil and check again.

[Andreasbest]

Re: Dell E6440 shortcircuit

Perhaps it will be faster to try with a bench PSU, inject 1W and see which one gets warm?

[mon2]

Re: Dell E6440 shortcircuit

Ok back...you can try that method but should be rather quick to remove the 2 mosfets. See if that resolves the short. If the short is fixed - suggest to replace BOTH mosfets.

If not, then it is all about the local caps.

[Andreasbest]

Re: Dell E6440 shortcircuit

Ok, i found the "guilty".
PC713 is short
Should i replace it or it work without it too?

[Andreasbest]

Re: Dell E6440 shortcircuit

"deleted"

[mon2]

Re: Dell E6440 shortcircuit

1) With PL701 lifted, you are only working with the dual mosfets and the local caps on the same rail.

Update - remove / lift one leg of PL700 as well - confirm the short is still there.

2) Before you start this next stage of testing - check on the resistance to ground for pin # 4 of the mosfet(s) = connects to pin 18 of the charger IC.

3) If you wish to inject a voltage - inject 1V and being a short to ground (or close to) - the part should heat up quickly since it was forcing the power adapter to shut off immediately.

At 1V - it should be safe enough.

You can dab each of the mosfets and local caps with alcohol and check which area evaporates the fastest - unless you have a thermal camera.

[Andreasbest]

Re: Dell E6440 shortcircuit

Ok, i found the "guilty".
PC713 is short
Should i replace it or it work without it too?

I found it meanwhile.
What do you suggest?

[mon2]

Re: Dell E6440 shortcircuit

Excellent !

The solder back the lifted part. The laptop should be fine without this part. If you have spares, apply a replacement but will not be a 'show stopper'.

Be sure to consider a similar or higher voltage rated part - to be safe. It is a jelly bean part and quite common on other logic boards.

0805 non-polarized capacitor @ 22uf (can be a higher capacitance as well) but 25v or higher is recommended.

[Andreasbest]

Re: Dell E6440 shortcircuit

Ok, MB is working fine. I will try to find another same cap to replace it, if no i'll leave it this way.
I'll follow the exact steps on the second E6440 and i'll return with news, thank you for coming so far with me and helped me : ))

[mon2]

Re: Dell E6440 shortcircuit

You are quite welcome.

[Andreasbest]

Re: Dell E6440 shortcircuit

You are quite welcome.

PC714 guilty on the second MB!
Thank you very much mate, i own beers to you too when you visit Greece : )))