Dell Latitude 5420 no power

[vpower]

Hi, I have this laptop that suddenly died. Motherboard is GDF40 LA-491P REV:2.0
I found the schematic here: https://www.badcaps.net/forum/troubl...-0-3-boardview
When I connect the type-c charger with a meter, no battery connected, I see only 5v and 2 amps current draw and these components quickly get very hot under thermal camera: UA1, PU601 and PU102
Any suggestion?

[mon2]

Flux and carefully remove UA1 - audio codec off the board. Test again without this audio codec off the board. Be sure that there are no shorted smd pads on the PCB after this part is removed.

[vpower]

Flux and carefully remove UA1 - audio codec off the board. Test again without this audio codec off the board. Be sure that there are no shorted smd pads on the PCB after this part is removed.

I'll try and let you know.
Maybe it is useful infomation...: when I check PU102 in diode mode both PIN2 LX_5V and PIN8 +5V_ALWP sound like shorted to ground and 6 ohm to ground in resistance mode

[vpower]

[QUOTE=mon2;n3514037]Flux and carefully remove UA1 - audio codec off the board. Test again without this audio codec off the board. Be sure that there are no shorted smd pads on the PCB after this part is removed.

UA1 removed, still same issue. I noticed lower current drain (1,5A instead of 2A) , still heatspots on PU601 and PU102

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance to ground at PL101 (inductor) - either side is ok.

PL101 creates the +5V_ALW power rail.

[vpower]

Remove all power. Meter in resistance mode.

Measure the resistance to ground at PL101 (inductor) - either side is ok.

PL101 creates the +5V_ALW power rail.

2 ohm

[mon2]

Most definitely too low. Locate a solder blob / jumper on the board with label PJP103. This is the blob that allows for the this power rail to travel to downstream devices so they can be powered.

Can you confirm if this is a solder blob? Post a pic if you can to confirm. If a solder blob, use solder braid and flux to remove this solder blob off the board. This process will isolate the producer and consumer sides of this power rail.

Then with no power, measure the resistance to ground again on each side of this removed solder blob. We need to confirm which side is shorted. Guessing it will be the consumer side = pin 2 of the solder blob.

[vpower]

Most definitely too low. Locate a solder blob / jumper on the board with label PJP103. This is the blob that allows for the this power rail to travel to downstream devices so they can be powered.

Can you confirm if this is a solder blob? Post a pic if you can to confirm. If a solder blob, use solder braid and flux to remove this solder blob off the board. This process will isolate the producer and consumer sides of this power rail.

Then with no power, measure the resistance to ground again on each side of this removed solder blob. We need to confirm which side is shorted. Guessing it will be the consumer side = pin 2 of the solder blob.

I confirm, it is a solder blob. I cleared it with braid and measured, left side is open circuit, right side is 2 ohm

[mon2]

Sorry - which side is consumer side? The now open side is the side with the inductor measured earlier?

Do you have an adjustable power supply? One that can be used to dial up 1v (recommended)?

If not, we need to keep hunting for the shorted part with some logic. Suspecting it will be linked to the USB port(s).

[vpower]

Sorry - which side is consumer side? The now open side is the side with the inductor measured earlier?

Do you have an adjustable power supply? One that can be used to dial up 1v (recommended)?

If not, we need to keep hunting for the shorted part with some logic. Suspecting it will be linked to the USB port(s).

once I cleared the short (solder blob), PL101 is no longer shorted (or low resistance). of course the contact on the right is shorted.. PIN 2 of PJP103 is shorted or very low resistance. I'll keep searching.