Lenovo Ideapad Gaming 3 15ARH05 NM-D191 processor voltages disappear at startup

[tomodachi]

MB schematic and boardview
https://www.badcaps.net/forum/troubl...86#post1802186

This one came in with no display complaint.
MB powering up with all CPU coil voltages of CPU and GPU present, appear to be drawing around 1 to 1.8 amps on boot cycle, then in 3 seconds CPU phases on PL3003,PL3002,PL3001,PL3000 disappear, leaving MB drawing only 0.25 amp with GPU core voltages still on.
Trying to power off pressing power button, 10 seconds of pressing ends up with self reboot with same cycle.

BIOS, EC firmwares are ok, CPU core IC RT3667 replaced, still same.
No corrosion, nothing suspicious.
Unit came in with very, very dirty and clogged fan, giving me idea of loose balls under CPU..

Any ideas will be appreciated.

[tomodachi]

MB schematic and boardview
https://www.badcaps.net/forum/troubl...86#post1802186

This one came in with no display complaint.
MB powering up with all CPU coil voltages of CPU and GPU present, appear to be drawing around 1 to 1.8 amps on boot cycle, then in 3 seconds CPU phases on PL3003,PL3002,PL3001,PL3000 disappear, leaving MB drawing only 0.25 amp with GPU core voltages still on.
Trying to power off pressing power button, 10 seconds of pressing ends up with self reboot with same cycle.

BIOS, EC firmwares are ok, CPU core IC RT3667 replaced, still same.
No corrosion, nothing suspicious.
Unit came in with very, very dirty and clogged fan, giving me idea of loose balls under CPU..

Any ideas will be appreciated.

Update

Mildly reflowed +VDDCR_VDD mosfets and two tantalum caps sitting across coils out of curiousity, motherboard booted succesfully, but after cool down it won't work again.
Tomorrow I will do a full resoldering and tantalum replacement and let you know results.

[mcplslg123]

Dying PCH due to overheating?

[tomodachi]

Dying PCH due to overheating?

Do you mean CPU itself ? Yeah quite possible. Reball might help

[mcplslg123]

Its ryzen APU and its known to have dryball joint issue.

[mcplslg123]

Before experimenting with reball,observe the status of 1.8V when core voltage disappears.

[tomodachi]

Before experimenting with reball,observe the status of 1.8V when core voltage disappears.

Thanks for the input. 1.8V was always present.
This one worked just fine after resoldering CPU core mosfets. Been testing for a day, so far its working.