Cpu_core signal missing. Lenovo g50. Help?

[Weelcup]

Hi friends.
I need help to trace the cpu_core signal as it is missing while all other voltages are present.

There is no 0volts at pin1 of the PU908 controller. I have changed the controller but still no luck. I have programmed the bios and the EC but same issue. The 5v source voltage is present in the PU908 controller. But there is no cpu_core signal.

I would appreciate any advise.

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

if nothing is shorted, measure voltage on all pins of PU908 to check which one is incorrect.

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

if nothing is shorted, measure voltage on all pins of PU908 to check which one is incorrect.

thanks for reply...
No nothing is shorted. and these are the measurements:

pins 2,3,4,5 ==> 1.055v
pins 15,28 ==> 5.055v
pin 7 ===> 20v
pin 8 ===> 4.65v

all other pins ==>0v

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

what is your mainboard ID? or upload its schematics.

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

what is your mainboard ID? or upload its schematics.

of course... the main board ID is ACLU/ACLU4 UMA NM-A362

and this is its schematics

THANKS for following up...

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

check which one of EC_VR_ON and CPU_VR_ON is missing?

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

check which one of EC_VR_ON and CPU_VR_ON is missing?

The cpu_vr_on is missing. 0v at pin1.

The EC_VR_ON is not connect to pin 1 as there is no fuse or resistor to connect it to pin 1.

Please check the attached pic

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

Probably, the problem is not related to PU908. Now measure voltage on Pins 97, 99, and 107 of IT8586E.

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

thanks for reply:

the measures are as follows:

pin97 = 3.4v
pin99, pin107 = 3.39v

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

which one of the following voltage rails is missing?
+1.5VS, +1.35VS, +1.05VS, +0.675VS

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

+1.5VS is missing ...

But 1.35VS, +1.05VS, +0.675VS are present

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

It seems PU602 has problem. So measure voltage on its pins.

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

I just checked it ….
PU602 pins voltages are as follows:

pin1= 0V
pin2= 0.8V
pin3= 1.52V
pin4= 1.52V
pin5= 3.3V
pin6= 5.0V
pin7= 0.56V
pin8= 3.3V

sorry I think I miss measured the +1.5vs and thought it was missing in my yesterday's measures... but it is present at PJ603

[mcplslg123]

Re: Cpu_core signal missing. Lenovo g50. Help?

In my opinion based on your reading, It seems inbuilt cpu+pch chip failure. thats the norm rather then exception on these mobo's.(I assume you have already flashed Main and Ec bios from known good dump)

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

In my opinion based on your reading, It seems inbuilt cpu+pch chip failure. thats the norm rather then exception on these mobo's.(I assume you have already flashed Main and Ec bios from known good dump)

Thanks for the advise...
however, I started to suspect the PCH. cuz I was measuring the voltages that PCH provides. I measured the following :
PM_SLP_S3#= 0V
PM_SLP_S4#= 0V
PM_SLP_S5#= 0V

But PM_SLP_SUS#= 3.3V as output at AP4 pinout and 2.5V when it entered pin87 of the EC...


Does the measures above suspecting the PCH failure??

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

since you said +5VS and +3VS are present, PM_SLP_S3# and PM_SLP_S4# and PM_SLP_S5# should have no problem. Now measure voltage on Pin 30 of IT8586E. If it is high, the PCH will probably become a suspect. then, turn it off and measure resistance on CPU_VR_ON.

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

since you said +5VS and +3VS are present, PM_SLP_S3# and PM_SLP_S4# and PM_SLP_S5# should have no problem. Now measure voltage on Pin 30 of IT8586E. If it is high, the PCH will probably become a suspect. then, turn it off and measure resistance on CPU_VR_ON.

IT8586E Pin30=0V.
the resistance of CPU_VR_ON=1.68K

however when I press the power button for a while the board doesn't shutdown, instead the led blink one time like a restart and keep on. I don't know if that could mean something. but I just noticed it.

[caspian]

Re: Cpu_core signal missing. Lenovo g50. Help?

Thus, PCH and IT8586E are possible suspects now.

[bluestone]

Re: Cpu_core signal missing. Lenovo g50. Help?

Check Ec pin 99 and pin 30

[Weelcup]

Re: Cpu_core signal missing. Lenovo g50. Help?

Thus, PCH and IT8586E are possible suspects now.

thanks Caspian. your help is really appreciated friend.