Need help with G50-70 NM-A271 .. power up no screen???

[Weelcup]

Dear friends.
I get sick of this motherboard. Everything is working except for no output or post on screen.
And after following the cpu signals then there are missing signals.

The cpu-core is missing. 0.07v on PL9 coil.
Following the schematics, I checked PU908 controller which provides the cpu-core. The 5v alws is present in the controller but there is no enable signal coming from the EC chip.
I have changed the ec chip and programmed it with couple of different dumps and I programmed the bios chip as well but still no luck .

I just wanted to know how the enable signal is generated in the EC. Should the EC recieve a signal from the PU908 or from the cpu in order to send enable volts to PU908?

Thanks for any advise in advance ..

[Weelcup]

Re: Need help with G50-70 NM-A271 .. power up no screen???

Dear friends.
I get sick of this motherboard. Everything is working except for no output or post on screen.
And after following the cpu signals then there are missing signals.

The cpu-core is missing. 0.07v on PL9 coil.
Following the schematics, I checked PU908 controller which provides the cpu-core. The 5v alws is present in the controller but there is no enable signal coming from the EC chip.
I have changed the ec chip and programmed it with couple of different dumps and I programmed the bios chip as well but still no luck .

I just wanted to know how the enable signal is generated in the EC. Should the EC recieve a signal from the PU908 or from the cpu in order to send enable volts to PU908?

Thanks for any advise in advance ..

Hi friends,
However there was no reply to my problem but thanks for everyone read it.
to be a beneficial post, I have finally solved the issue by replacing the two mosfets PQ39 and PQ40. the laptop powers up normally no heating on GPU chip or the cpu.

thanks again

[Chieftain]

Re: Need help with G50-70 NM-A271 .. power up no screen???

Hello friend... I had the same problem with you but I resolve it with another way..
I reflash the Bios just to be sure. The laptop still didn't post... I removed the BIOS battery totally.. After pressing the power button it starts to blink the red led and after few seconds it posted... I replace the battery with new to be sure and the laptop is working fine...
Propably you had another damage in mosfets and we had deferent issue,..

[Weelcup]

Re: Need help with G50-70 NM-A271 .. power up no screen???

Hello friend... I had the same problem with you but I resolve it with another way..
I reflash the Bios just to be sure. The laptop still didn't post... I removed the BIOS battery totally.. After pressing the power button it starts to blink the red led and after few seconds it posted... I replace the battery with new to be sure and the laptop is working fine...
Propably you had another damage in mosfets and we had deferent issue,..

Thanks a lot for sharing your experience.. really appreciated.
The issue with mine was very weired. As the old mosfet seemed to work when i tested it on another board.

I had already made those steps ( cleared ME and reflashing bios and of course replacing the CMOS battery) ..

Glad that you had resolved yours by flashing the bios. These lenovo models had plenty of issues. Mainly with the IO chip. I believe this motherboard design lack of protection measures and component qualities.

Thanks again