Dell E6540 shortcircuit. Cuts off charger.

[Andreasbest]

Hello!
Today i got a completely and absolutely dead Dell E6540 with burnt FDS6679AZ (PQ4) which i replaced it with a AO4407A.
Now the charger indicates a shortcircuit somewhere and cuts off when i plug it on laptop so i need your help to find it.
I attach photos of the motherboard (before replacement of PQ4) and diagram (PQ4 circuit is on page 60)
Thank you in advace!

[RJARRRPCGP]

Re: Dell E6540 shortcircuit. Cuts off charger.

Those wet-looking spots, may be a spilled beverage.

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

It's liquid from the fried mosfet, cleaned up by now.
Still searching for the short-circuit.

[Sametbey]

Re: Dell E6540 shortcircuit. Cuts off charger.

Short circuit appears on the + 19V line. You should scan for short circuits by disengaging jumpers such as PL504 and PJP600.

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

hi
is the short before or after PQ4

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

hi
is the short before or after PQ4

Hi. It's after PQ4, when the burned mosfet was still on board the charger didn't cut off.

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

Short circuit appears on the + 19V line. You should scan for short circuits by disengaging jumpers such as PL504 and PJP600.

Hi. I'll be on the bench in a while, i'll check the jumpers and let you know.

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

Short circuit appears on the + 19V line. You should scan for short circuits by disengaging jumpers such as PL504 and PJP600.

PL504 is not present in motherboard
PJP600 removed but shortcircuit occurred again

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

remove the CPU and apply voltage to the shunt resistor using a laboratory power supply.
And check witch component was heated I think that is an bad capacitor

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

the colleague means all PWR_SRC relevant jumpers
e.g. PJP 200/300/700 and PL700

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

remove the CPU and apply voltage to the shunt resistor using a laboratory power supply.
And check witch component was heated I think that is an bad capacitor

I was thinking on doing that too, what do you mean "shunt resistor"?

[mon2]

Re: Dell E6540 shortcircuit. Cuts off charger.

https://eepower.com/resistor-guide/r...unt-resistor/#

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

I applied 19V with 1A limiter but i see no heat in any component.
Shall i raise the limit?

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

Pr701

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

yes 2A

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

Have you an thermal cam ?

[mielta]

Re: Dell E6540 shortcircuit. Cuts off charger.

With some devices, the temperature difference is small

[Sametbey]

Re: Dell E6540 shortcircuit. Cuts off charger.

I guess don't inject voltage from the PR701 (bypassing the input mosfets). If there is a short circuit after PR701, problems may occur in other chips. As I mentioned in the previous article, examine the + 19V line by separating the coils and jumpers. How much current was drawn when you gave 19v.

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

I tried with 2A and nothing happened either, so i desolder PR701 to isolate the left upper left part of the mb and that resulted in burned PU800.
Seems like the mb has more than 1 shortcircuits, i'll probably waste it.

[Andreasbest]

Re: Dell E6540 shortcircuit. Cuts off charger.

I guess don't inject voltage from the PR701 (bypassing the input mosfets). If there is a short circuit after PR701, problems may occur in other chips. As I mentioned in the previous article, examine the + 19V line by separating the coils and jumpers. How much current was drawn when you gave 19v.

9V only