Lenovo G50-80 turns on and quickly shuts down

[mnciks11]

Hello guys, i need your help fellow brothers

Im diagnosing a Lenovo G80-50 laptop

ACLU3/ACLU4
Rev : 1.0

when you press the power button, the LED power light turns On and quickly shuts down, no display, fan spins a sec and stop. I haven’t seen any short so far.
PU908 (CPU POWER CORE CHIP) is getting hot the moment you press the power button, the laptop turns off very fast, i changed PU908, still im getting same problem, on output side of the 2 cpu power supply coil i get 1.6v and then goes away as soon as the laptop turns off, still the new chip get hot as well and the pc quickly shuts down

The funny thing is, when i remove both mosfets that generates power for the CPU, the laptop doesn’t switch off at all, but when i place them back it switch off very fast

Kindly advise guys

[ktmmotocross]

Re: Lenovo G50-80 turns on and quickly shuts down

1.6V is way high i think. replace all mosfets on cpu rails

[piernov]

Re: Lenovo G50-80 turns on and quickly shuts down

1.6V is ok on Haswell. Replacing the MOSFETs at the same time as the controller can still be a good idea though.

[mnciks11]

Re: Lenovo G50-80 turns on and quickly shuts down

Thank you guys, i just did replace those 2 mosfets, but still no lucky, i replaced the chip too

[guzica]

Re: Lenovo G50-80 turns on and quickly shuts down

Your CPU is defective!

[mnciks11]

Re: Lenovo G50-80 turns on and quickly shuts down

Your CPU is defective!

I think i agree with you, if i remove the output mosfets of the cpu power supply the board turns On without quickly shutting down, it turns on and never shut down..but if i put the mosfets, it turns on and get 1.6v on the output coil of the cpu power supply abd then quickly shuts down

[lapfix]

Re: Lenovo G50-80 turns on and quickly shuts down

I m agree with Ktmmotocross ,1.6V is way high .
1.2 volts is quite low in terms of safety and heat. With an i5 and stock cooling, 1.1V is probably safe; with a Pentium and stock cooling, 1.2V is probably safe; with an i7 and stock cooling, maybe only 1.05V is safe (in terms of temperatures).

[piernov]

Re: Lenovo G50-80 turns on and quickly shuts down

Read post #3 again.

[guzica]

Re: Lenovo G50-80 turns on and quickly shuts down

1.6v is ok!

[khelane]

Re: Lenovo G50-80 turns on and quickly shuts down

Post 3 is true ,
Replace MOSFETs
Or CPU is defective

[perzyk23]

I confirm. I replaced mosffets q39 and q40. When they are gone, the board works, but when I put new ones in, the effect is unfortunately the same. My processor is damaged.