lenovo legion y520 b391 no picture

[myth77]

The motherboard have all the voltages on gpu, dram, pch and cpu but will not output picture.

readings on lcd connector while lcd connected:

+lcd_vdd 3,3 v
PCH_EDP_HPD 3,3v
but
DISPOFF# 0v
INVT_PWM 0v

the resistence to gnd on INVT_PWM is 94 kohms, and on DISPOFF# 98 kohm
As far as i can see DISPOFF# is coming from ite and INVT_PWM from pch...what is first? is DISPOFF# prequest for INVT_PWM to rise? or?

i tried different bios but the same. any ideas?

[hardware1]

Re: lenovo legion y520 b391 no picture

So now you have a Backlight issue not a Picture issue? because your picture voltages are present. As i know these signals (DISOFF#, INVT_PWM) are for LCD Backlight.
did you connect your laptop with an external Display from HDMI?
did you measure the Hall sensor signal (LID_SW#)?

[myth77]

Re: lenovo legion y520 b391 no picture

So now you have a Backlight issue not a Picture issue? because your picture voltages are present. As i know these signals (DISOFF#, INVT_PWM) are for LCD Backlight.
did you connect your laptop with an external Display from HDMI?
did you measure the Hall sensor signal (LID_SW#)?

Lid_sw# is ok...around 3.2V. On hdmi there is nothing...but could be locked in bios...

[mcplslg123]

Re: lenovo legion y520 b391 no picture

Are you sure mb is posting?? Try with a usb keyboard and see if numlock light is glowing. However, i doubt its not posting. If thats the scenario, no point troubleshooting edp pins for voltages.

[myth77]

Re: lenovo legion y520 b391 no picture

Yeah i missed that...the board is not posting...although all voltages present...even vcc+ but no numlock light on external keyboard. So, now i am facing either bios corrupted, ite corrupted or even dead cpu?

[hardware1]

Re: lenovo legion y520 b391 no picture

Yeah i missed that...the board is not posting...although all voltages present...even vcc+ but no numlock light on external keyboard. So, now i am facing either bios corrupted, ite corrupted or even dead cpu?

try with new bios. post your old file there and someone will help you.
https://www.badcaps.net/forum/forumdisplay.php?f=40

[mcplslg123]

Re: lenovo legion y520 b391 no picture

No harm in trying a bios flash(clean me) but make sure to take backup. Check whether its 1.8V or 3.3V chip and then proceed to flash. Btw, is there a ram slot or memory is onboard without any ram slot??

[myth77]

Re: lenovo legion y520 b391 no picture

I uplouded my dump....
there is no ram soldered on board...only two slots for memory.

[mcplslg123]

Re: lenovo legion y520 b391 no picture

You need to post your backup bios in "Bios Section" only and make a request for clean me bios. Update us about result.

[myth77]

Re: lenovo legion y520 b391 no picture

so i tried with bios ME cleaned nothing, not posting
i tried new ite....but same...not posting...all the voltages but no post.
So now its dead cpu or pch? right?
any other ideas?

[Sephir0th]

Re: lenovo legion y520 b391 no picture

Sometimes a negative capslock test is false negative. So I recommend to check again with a windows preinstalled SSD/HDD whether you get external picture. If still nothing, then share whether PLT_RST# and DRAM_RST# (or similar naming) is deasserted or not. Check and report pls

[myth77]

Re: lenovo legion y520 b391 no picture

Sometimes a negative capslock test is false negative. So I recommend to check again with a windows preinstalled SSD/HDD whether you get external picture. If still nothing, then share whether PLT_RST# and DRAM_RST# (or similar naming) is deasserted or not. Check and report pls

Nothing with ssd

PLT_RST# 3,27 vol
PCH_DRAMRST# 1,25 vol

[mcplslg123]

Re: lenovo legion y520 b391 no picture

Hmm. Everything seems to be in order and its difficult to suggest anything further. If you have DSO, check activity on LPC LAD/Frame/CLK.