Dell Latitude E5480 (LA-E081P) not work from AC adap.

[bushmann]

Dear all,

Please can someone help me.

motherboard LA-E081p re. 2.0.

In short, this motherboard had an ISL88738HR chip on pin 17 "DCIN".
I found burnt components PD901, PR916 and missing PD4 "NB-PSID".
I replaced everything, but it still doesn't want to work from the power supply, I tried 65W and also 130W original DELL.
It starts from the battery, but I don't have an original battery for this model, so it says in the BIOS that it is not an original battery and cannot charge it.
Now the question is whether it is necessary to have a battery to run from the power source.
Input mosfets PQ9 and PQ4 are open.
I don't have +5V_alw or +3V_alw at all.
The measurement on the charger ic is on picture 01.
There is no short circuit and 0V on the PSID.

[mon2]

Re: Dell Latitude E5480 (LA-E081P) not work from AC adap.

Hi.

1) Measure and post the voltages on each pin (source, gate, drain) of the DCIN mosfets @ PQ9 and PQ4 with the external adapter attached. For this test, remove the battery so the focus is on the adapter operation.

Meter in 20v or higher DC scale. Red meter probe on pin to test; black to ground on the logic board.

2) Next, remove all power / no battery. Meter in resistance scale (start with the lowest for now).

Measure the resistance across the same mosfet pins as follows:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

We are checking for a low resistance reading = defective mosfet. If you see '1' or 'OL' then switch to the next higher scale on your meter till you have a reading.

Post the resistance readings for these mosfets AND the meter scale used for each measurement.

Often, these DCIN mosfets get damaged and need to be replaced. See the detailed sticky thread above from @Piernov.

3) The PS_ID pin is important and Dell likes to use this single line for a single-wire communication to extract parameters from the Dell branded adapters. If the communication does not proceed then the BIOS will complain. However, you are not quite there yet so for now, work on the electrical repairs and then we can review the PS_ID portion of the logic board.

While you are in voltage mode on your meter, what is the voltage on:

a) pin # 1 = PS_ID of the power connector ?

b) PS_ID @ pin # 1 of PR4 ? Not expecting a value here since the pull-up resistor will not be active since your +3.3_ALW is not yet working...

[bushmann]

Re: Dell Latitude E5480 (LA-E081P) not work from AC adap.

So, in the end there was a defective new charging chip that I changed there.
I put the second one and everything started working.

[mon2]

Re: Dell Latitude E5480 (LA-E081P) not work from AC adap.

That detail was not mentioned in the first post. Good that it is now working.

[bushmann]

Re: Dell Latitude E5480 (LA-E081P) not work from AC adap.

oops, yes you are right, I forgot to write there that I replaced this chip with a new one.
I will be more careful when writing in the future.

Thanks