Dell Inspiron 3521

[azhar2006]

Hello all
I have a motherboard type (compal_la-9104p_r1.0) explained the problem in this picture.
The problem in PQ101 was damaged and I replaced it with a MOSFET bearing the number (AO4407A)
The resistors were measured and were intact.
Thanks in advance.

[Mazorca]

Re: Dell Inspiron 3521

Your problem might lay somewhere else.
There should not be a voltage drop thru PQ100, from 19.v to 18.0v. Measure carefully, 19.XXv and 18.XXv. Looks like you are measuring the voltage thru the internal diode, and this is a P-mosfet, no voltage drop whatsoever, and voltage drop should be around 0.7v if it's not working. Measure Vgs, again, should be higher than 25v, yours is way too low, 18v.

[piernov]

Re: Dell Inspiron 3521

PQ100 is probably fine. Still make sure that both MOSFET (PQ100 and PQ101) are not shorted.
The issue is with the gate voltage on both MOSFET (gates are tied together). It should be lower than 18V for PQ101 to let the current flow. (they are P-channel MOSFET)

You have to check ACOFF (on PR133) and ACIN (on PR139 or PU100 pin 13) signal.

[azhar2006]

Re: Dell Inspiron 3521

Happy evening to everyone
Thank you so much
Yes, there is a decrease in the voltage from the other side from 19 volts to 18 volts on the PQ100, while the PU100 is originally not found on the motherboard, it has been removed from the mother motherboard because it is damaged and the presence of high temperature in it.

Where are the PR133 and PR139 resistance ?

[piernov]

Re: Dell Inspiron 3521

Nevermind, this one is not labelled on the board…
Instead of PR133 and PR139 you could measure all pins of PQ109.
However, PU100 is needed for the board to turn on. You need to replaced it first.

[Mazorca]

Re: Dell Inspiron 3521

piernov: " It should be lower than 18V for PQ101 to let the current flow"
I stand corrected, sorry for the wrong advice. Lower for P, higher for N.

[azhar2006]

Re: Dell Inspiron 3521

Thank You So Much Dear Mazorca
But do not get less than 18 volts on the gate PQ101
Is not ISL88731C the reason for it? Or is there a problem elsewhere?

[Mazorca]

Re: Dell Inspiron 3521

My knowledge doesn't extend that much. Like piernov said, measure all pins on pq109, and if you have a bench power supply, (advice: get one), test if PU100 is getting hot, internal shortage.

[azhar2006]

Re: Dell Inspiron 3521

OK Mazorca and piernov
I found something when I removed PQ101 from the motherboard got the following voltages on the PQ100, the ideal voltages (1, 2 ,3), 19 volts, and get 7 volts on pin 4.
I think that (AO4407) is not equivalent to MOSFET (AO4409)
This is the equivalent

[Mazorca]

Re: Dell Inspiron 3521

All I could tell is that AO4407 is rated for 12A and AO4409 is for 15A. Replace with equivalent or higher. Test first for shorts or open. Voltage at gate at pin4 PQ100 looks correct, should be same at pin 4 pq101, they are connected.

[piernov]

Re: Dell Inspiron 3521

Indeed the MOSFET should be replaced with one with the correct rating. But this is not your problem if the replacement MOSFET is not shorted and is oriented correctly.
You need to replace ISL88731C first before trying anything else.

[azhar2006]

Re: Dell Inspiron 3521

Yes piernov I have replaced ISL88731C Was it the reason?

[mcplslg123]

Re: Dell Inspiron 3521

Dear Azhar2006, was you able to fix this?? i'm having same issue