820-02016 - No image/backlight

[overshoot]

Hello,

This is a board issue. I've tested with board another good working screen, same symptoms.
Client's screen works with test MB.
Works with external display as a secondary monitor.

Here are some measurements:
edp_panel_1v8_en = 1.8V
pp3v3_sw_lcd = 3.3V
pp5v_sw_lcd = 5V
bl_pwr_en = 0V
lpdp_int_hpd = 0V

I've checked the voltage drops on all the LVDS connector pins and they seem to be in the range with the flexbdview data.

Board is pristine, couldn't find any visual defect or corrosion, etc...
What else can I check before assuming CPU is shot please?

 

[2informaticos]

"lpdp_int_hpd = 0V"
LCD must send high level there; else CPU can't recognize it.

Any history available?

 

[overshoot]

unfortunately not as client said it stopped working out of the blue.
I've also checked IPD_LID_OPEN_1V8 and it's present at 1.8V

I've checked again that lpdp_int_hpd_3v3_conn and it's not even pulsing.
What could cause that signal to be missing?

 

[2informaticos]

Check diode mode to ground at LPDP_INT_HPD.
Remove RP600 and check again DP_INT_HPD_3V3_CONN voltage (LCD attached).

 

[overshoot]

I've got .313V with the resistor in place and .465V without.

 

[2informaticos]

If the connector and small video cable are good, then bad CPU...