Only the power LED: ThinkBook 15-IIL

[fk-shokai]

Hello! Please help me.

ThinkBook 15-IIL(M/B DALVACMB8D0 Rev) won't start.
When I connect the power adapter, the battery LED, power LED, and access lamp will light up, but after a while the access lamp will start flashing.
The monitor backlight does not light up and the CPU fan does not spin. CPU and RAM sockets are getting very hot.
Any ideas?

: Already implemented
・Full cherge and Full discharge battery.
・Replace SSD & RAM
・Replace CMOS battery

Thank you.

[mon2]

CPU and RAM sockets are getting very hot.

This is of concern. Remove all power. Meter in resistance mode. Measure the resistance to ground of the VCORE inductors that power the CPU. What may have happened is that the high side mosfet(s) may have leaked and under this event, the high adapter voltage will pass through onto the very low voltage rails used by the CPU. Then this will become a no repair. Unfortunately, this happens often on laptops.

The multiple inductors used by the multiple power rails that operate in phases to keep the logic board power supplies cool should be located nearby the CPU. Each such inductor / rail takes turns to turn ON then OFF when another takes it's turn to do the same. This way, no single power rail is burdened by the heavy current demands of the pig CPUs.

[fk-shokai]

Dear mon2
Thank you for your reply.

I am currently studying surface mount components, and I understand that a high side MOSFET is a component like the one in the image. I tried measuring the resistance values of the three terminals of a MOSFET at multiple locations. However resistance values varied greatly, and sometimes no value was obtained...
Looks like I'll have to actually look at the circuit diagram.
This time I purchased the machine as a teaching material, so even if the worst case scenario requires a CPU replacement, I may still carry it out