Dell XPS 9300 13” motherboard FDQ30 LA-H811P rev 1.0 works with battery only

After opening jumper, always 3,4V
Do you know coil PL 401 value?
On PL401 (jumper side) I measure 0,2V without coil.

Measure the resistance to ground on the system side (pad close to the chip PU200) of the jumper PJP400.

valieromarco napisal/-a:Do you know coil PL 401 value?

PL401= 1.5µH / 7.2ADC (11ASAT), 20%, dimensions: 5.19 x 5.18 x 3mm

Resistance is 1,3 Mohm

Measure the resistance to ground on pin 8 of chip UC28.

Goes up quickly from 5 M ohm to OL

Try to replace the chip PU400 (NB502GQ-Z).
If you don't have this chip, you can swap the chips PU400 and PU401 with each other (they are the same).

After replacing the chips, turn on the board with the jumpers PJP400, PJP401 opened to make sure you are getting correct voltages (5V) on the coils PL401, PL403. If so, close the jumpers and test the board again.

So after that if all is ok I have to replace PU400?

Yes, you have to.
If you swap the chips PU400 and PU401 with each other, and in case the PU400 is damaged, you will likely notice that the chip PU400 will not work properly in the place of PU401.

Unfortunately the situation is the same

Upgrade 01.00 AM



Accidentally I touched a capacitor with my multimeter and now voltage on PL401 is 0V
I swap them again and I got voltage again but 4,4V without PL401 and around of PL401 zone PCB is warm
So P401 is damaged

Resistance to ground of PL401
Side PU400 = 270kohm
Side system = sometime drops to 42Kohm sometime rise to 42Kohm

Pin401 resistance to ground

1= 2,56 Mohm
3= rise up to 9,5 Mohm

Remeasure the voltages to ground on pins 1, 3, 10, 12, 13, 15 of chip PU401 with the coil PL401 installed.

PU401

1=8,4
3=3,5V
10=5,3V
12=0V
13=1V
15=3V

valieromarco napisal/-a:Accidentally I touched a capacitor with my multimeter and now voltage on PL401 is 0V
I swap them again and I got voltage again but 4,4V without PL401 and around of PL401 zone PCB is warm
So P401 is damaged

Something is not right here. The coil PL401 belongs to the chip PU400, while the chip PU401 belongs to the coil PL403. About which chip/coil exactly you are talking about?

I wrote PU401 because I replaced PU400 with PU401
Now chip damaged is solder on PU401 with open jumper.
Working chip is solder on PU400

valieromarco napisal/-a:and now voltage on PL401 is 0V

You stated that there is 0V on the coil.

valieromarco napisal/-a:PU401
13=1V

But this measurement shows that the voltage on the coil PL403 should be about 3V and not 0V.
Please, check your measurements.

Ok I understand the mistake
I measured PU400 not PU401 because is 5V the power rail is missing, and I read PU400 instead of PU401.
Sorry.

So to measure 3V power rail power I have to swap chip again.
I’m going to swap them.

PU401 with jumper pjp401 open and pjp400 open and with PL401 installed

1=8,4
3=3,53
10=6V
12=0V
13=1,2V
15=0,44V

No one requested to exchange the chips with each other again.
However, everything is mixed up here. No one knows which chip/coil we are talking about anymore.

Let's start again from the beginning:
- Measure the resistances to ground on coils PL400, PL403.
- Measure the voltages to ground on pins 1, 3, 10, 12, 13, 15 of the chip that is currently soldered to the place of PU400.
- Measure the voltages to ground on pins 1, 3, 10, 12, 13, 15 of the chip that is currently soldered to the place of PU401.

Ok sorry
I will measure all again, just remember that one of two chip is damaged let me know where is better solder damaged chip?

If you know that the chip is damaged, replace it immediately
There is no point in wasting time diagnosing a chip that we already know is damaged.

After replacing NB502GQ

PL 401= 36,8Kohm and voltage = 3,6V after some minutes drops to 2,78V
PL403 = 36,9Kohm and voltage. = 3,45V after some minutes drops to 2,63V

PI 401
1=8,3V
3 =3,55V
10=6,5V
12=0V
13=0,62V
15 =3V

1=8,3V
3=3,5V
10= 5,6V
12=0V
13=1V
15=3V