Dell Latitude 5420: No charge, no boot; amber LED for as long as the power button is held.

[BTubbs200]

Dell Latitude 5420 P137G
Board model LA-K491P REV A01

Laptop is stone dead and only reacts to the power button being held while the charger is plugged in, in which case a dim amber LED fades in and immediately fades out when I let go. Battery being plugged/unplugged does not change anything.
CMOS battery was removed and reinstalled; no change.
No shorts to ground have been identified on the board whilst probing the power rails in resistance mode. No visibly damaged components.
No indication that the CPU is receiving power; CPU fan does not activate.
Of the two USB-C charging ports, one appears to supply vastly less voltage to the board than the other. Such as supplying less than 2V to PC630 while the other supplies 16.84V.

Some voltage measurements around the board while the charger is plugged into the "good" port:

PC520: 16.84V
PC575, PC576: 0V
PC630, PC631, PC632: 16.84V
PC715: 0V
PC1066: 0V
PC1067: 0V

PL100: 4.18V
PL201: 0V
PL301: 0.06V
PL501: 0V
PL601: 5.14V
PL602: 0V
PL603: 0V
PL701: 4.32V

Board produces some audible coil whine/hissing noise when placing ground probe of multimeter on a screw hole, slightly flexing the board, etc.

Any insight would be appreciated and I'll do my best to answer any clarifying questions 🙂

[diamesa]

I have a similar issue that I posted at page 2 of this Thread:

https://www.badcaps.net/forum/troubl...-5000-no-power

Same amber light whenever I press the power button, but nothing else. Could our CPU be dead?

[quadri234]

It seems your problem is dc to dc converter at the standby section

[BTubbs200]

I have a similar issue that I posted at page 2 of this Thread:

https://www.badcaps.net/forum/troubl...-5000-no-power

Same amber light whenever I press the power button, but nothing else. Could our CPU be dead?

I still haven't solved this problem but have narrowed it down considerably. I'm fairly confident the CPU/PCH is still good, there's nothing to suggest either is dead, power rail isn't shorted. My current hypothesis is that it's a dead PD or EC chip.

[BTubbs200]

It seems your problem is dc to dc converter at the standby section

Elaborate? Does one of my 0v readings correspond to the standby converter?

[diamesa]

I have a similar issue that I posted at page 2 of this Thread:

https://www.badcaps.net/forum/troubl...-5000-no-power

Same amber light whenever I press the power button, but nothing else. Could our CPU be dead?

HEY! I desoldered the 2 FLASH IC's and reprogrammed them using the files found in the forum.

I could not take a dump of the 16MB one because I lost the chip, lol. (Had to buy another one). But at least the 8MB one was completely different to what I expected.

After reflashing and resoldering this the Amber light was gone and the laptop was trying to boot with a solid white light!
I will let you know if the laptop worked after I assembly it together again. But you should definitely try it!

[BTubbs200]

HEY! I desoldered the 2 FLASH IC's and reprogrammed them using the files found in the forum.

I could not take a dump of the 16MB one because I lost the chip, lol. (Had to buy another one). But at least the 8MB one was completely different to what I expected.

After reflashing and resoldering this the Amber light was gone and the laptop was trying to boot with a solid white light!
I will let you know if the laptop worked after I assembly it together again. But you should definitely try it!

I had reflashing bios in the back of my mind, unfortunately I decided to go a different route and botched a PD controller replacement. Board is completely dead at the moment.