No signal + 3VS_LCD on ASUS X451CA.

[karlox]

Hi, I have a problem with an ASUS X451CA MB, I have no signal + 3VS_LCD. I have the doubt if the PCH administers this signal. The equipment turns on but does not give a video signal, however the oscilloscope records output data in PCH. Any ideas? Thank you.

[karlox]

No signal + 3VS_LCD on ASUS X451CA.

I found that the + 3VS signal exists and arrives at the QM3002m3, but the + 3VS_LCD signal does not come out, what am I doing wrong?

[myth77]

Re: No signal + 3VS_LCD on ASUS X451CA.

what are the readings on q4601?

[zhang]

Re: No signal + 3VS_LCD on ASUS X451CA.

Hi, I have a problem with an ASUS X451CA MB, I have no signal + 3VS_LCD. I have the doubt if the PCH administers this signal. The equipment turns on but does not give a video signal, however the oscilloscope records output data in PCH. Any ideas? Thank you.

would you mind sharing the boardview?
I have the 2.0 & 2.1 version
but it seems to be differrent from yours ( based on the image of your post )

[karlox]

Re: No signal + 3VS_LCD on ASUS X451CA.

what are the readings on q4601?

In resistance
1 000.4
2 095.7 k
1,083 m
4 000.4
5 101.8 k
6 101.8 k


Voltage

1 -001.1 mV
2 000.8 mV
3 -000.9 mV
4 -001.0 mV
5 3,260 V
6 3,260 v

[karlox]

Re: No signal + 3VS_LCD on ASUS X451CA.

would you mind sharing the boardview?
I have the 2.0 & 2.1 version
but it seems to be differrent from yours ( based on the image of your post )

Sure.

[karlox]

Re: No signal + 3VS_LCD on ASUS X451CA.

what are the readings on q4601?

Well this seems to be the problem, the pin + 3VSLCD_EN has no output, I already removed it and I have that pin 16V. I will look for a replacement.

[karlox]

No signal + 3VS_LCD on ASUS X451CA.

Come back, I still have no video signal, the mosfet q4601 seems to think it was the problem, look for a replacement and install it but when you put it the signal is + 3vs_lcd. Checking the diagram, a line goes to the PCH, I think I suppose to have a fault there or it is dead. Any ideas?

[zhang]

Re: No signal + 3VS_LCD on ASUS X451CA.

I think you could try to remove q4602, and try to "jumper" or whatever its name is from drain to source
and are you sure that the notebook is in "normal state" unless for it's display?

[myth77]

Re: No signal + 3VS_LCD on ASUS X451CA.

As far as i can see to open +3vs_lcd_on mosfet q4602 you have to have +3vslcd_en signal which is generated through q4601 mosfet. And to generate that signal you have to have l_vdden_pch which is generated through pch. So its either pch dead or problem with the bios...

[karlox]

Re: No signal + 3VS_LCD on ASUS X451CA.

As far as i can see to open +3vs_lcd_on mosfet q4602 you have to have +3vslcd_en signal which is generated through q4601 mosfet. And to generate that signal you have to have l_vdden_pch which is generated through pch. So its either pch dead or problem with the bios...

PCH damaged, replaced and now running. Thank you