Dell E7450 not charching La-A961P

[arber1232]

HI, how are you. I have a dell laptop which does not turn on with charger and not charching
the light of the power button for a while and turns off, with battery the laptop turns on and works fine. I have done some measurements and I doubt Pq705 but I want your help to be sure....
Some measurements of pq 705 with charger without battery
D1-19,13y
S1/D2- voltage change 12v to 10v 13v
G1- voltage change 13v, 14v, 16v
G2-ov
S2-gnd

[arber1232]

Re: Dell E7450 not charching La-A961P

hi, how are you. I have a dell laptop which does not turn on with charger and not charching
the light of the power button for a while and turns off, with battery the laptop turns on and works fine. I have done some measurements and i doubt pq705 but i want your help to be sure....
Some measurements of pq 705 with charger without battery
d1-19,13y
s1/d2- voltage change 12v to 10v 13v
g1- voltage change 13v, 14v, 16v
g2-ov
s2-gnd

[MOD EDIT]
Schematic - https://www.badcaps.net/forum/showthread.php?t=73364

[mon2]

Re: Dell E7450 not charching La-A961P

Be sure the adapter is original and of the correct power rating.

Measure the voltage to ground of NB_PSID. This is from the power adapter center pin but on the logic board.

Post the measurement.

[mon2]

Re: Dell E7450 not charching La-A961P

Next, check on the charger IC, the voltage to ground of:

VCC
REGN
ACDET

Pins. Do connect the adapter. Post each measurement.

[arber1232]

Re: Dell E7450 not charching La-A961P

Be sure the adapter is original and of the correct power rating.

Measure the voltage to ground of NB_PSID. This is from the power adapter center pin but on the logic board.

Post the measurement.

i try with 2 Adapter

NB_PSID-3,2v
VCC- Change to 10v 12v 13 v
REGN-5.3v
ACDET-3,1v

[mon2]

Re: Dell E7450 not charching La-A961P

Ok. Focus on VCC - it should be stable.

Measure the voltage to ground before PR708. Is it stable ?

Then measure BEFORE PD704. This diode should provide a low voltage drop from the power adapter and then power the VCC rail but it should be stable.

Once this VCC is stable, then REGN should be ~6 volts. Confirm it.

[arber1232]

Re: Dell E7450 not charching La-A961P

Measure the voltage to ground before PR708. Is it stable ? Yes 19,34 volt
I find problem is PR708 CHANGE OHMS
I CHANGE AND NOW WORK OK

[mon2]

Re: Dell E7450 not charching La-A961P

Remove all power. Meter in resistance mode.

Check the resistance across the 2 pins of PR708.

Next, still with no power -> measure the resistance to ground of the VCC pin on the charger IC. We are checking for a low resistance on the VCC pin which may be causing the voltage to fluctuate.

What are the resistance readings ?

[arber1232]

Re: Dell E7450 not charching La-A961P

Thank you, pr708 had changed the value from 10 ohm, it was somewhere around 2.7 kohm

i change pr and laptop turn on and charging

[mon2]

Re: Dell E7450 not charching La-A961P

Well done