Lenovo legion 5 pro startup issue

[shahnld]

Good day Experts
I have a lenovo Legion pro 5 16ACH6H with AMD RYZEN 7 5800H and RTX3070,.

A weird issue has troubled me. If i power on off the laptop 20 times then only power LED will lit but no fan spin no display. At this stage gpu, vram. DDR voltage. 5v 3.3v 1.8v and the rest are present and cpu core is stuck at 0.84v.

And sometimes lets say the 21st time it will boot perfectly and there is image and everything is working perfectly and at this stage i see cpu core voltage is floating between1.15v and 1.34v.

and if i power it down and power on again then i have the same issue and it takes 20, 30 times ON Off cycle until it will start as normal..

Out of curiosity i reballed the cpu also changed cpu from a good working board but its still the same. I replaced cpu core pwm IC no effect. Bios flashed to newest version no change. EC is replaced and flashed no change.

Does anyone has ever encountered this issue or maybe can give me some instructions where the issue may be..?

Any help is much appreciated.

Kind regards..

[davidebeatrici]

I have just acquired a 16ACH6H with seemingly the same issue but in my case I never got it to POST.

After a deep investigation I suspected either PU1001 (RT3664BEGQW) or UC1 (CPU) is defective, because both CPU_PWROK and CPU_RST_R_N stay close to 0V and only the GPU heats up noticeably.
CPU_PWR_GOOD, EC_SYS_PWROK and SYS_RESET_N are 3.3V. Current absorption from VCORE is 0.3A at 0.8V.
Reflowing the CPU didn't have any effect. Adding RC97 (as shown in both schematics and boardview) increased CPU_PWROK slightly making it 0.226V.

With "replaced cpu core pwm IC" you're referring to PU1001, right? Because in that case, considering you also replaced the CPU, there must be something on the board that the IC doesn't like. Perhaps instability on the phases at startup, latching a fault condition?

My motherboard is a NM-D562 Rev 2.0 with an RTX 3060, what about yours? Also, could you share your voltage measurements, please?