820-00840 - No Backlight/Video

[menatwork]

The Board is Pretty Much Clean.
No external video as well.

Here is some measurements:

With Screen:
PP3V3_S0SW_LCD = 0V
PP3V3_S0SW_LCD = 0V
DP_INT_HPD = 0V


Without the screen:
BUF_EDP_PANEL_PWR_EN = 0V
PPVOUT_S0_LCDBKLT = 0V
BKLT_SD = 12.85V
PP5V_S0_BKLT_A = 5V
PP5V_S0_BKLT_A = 5V

PP3V3_G3H = 3.4

PPVCCSA_S0G = 0.7V
PP1V_S3 = 0.93V

Diode Mode:
PPVOUT_S0_LCDBKLT 1.200

U8400 Replaced
Tested with a different screen.


Any hint?
Thank you

 

[2informaticos]

I would not search for video, before assuring USB activity...

 

[menatwork]

Yes, i have USB/MOUSE activity.

 

[2informaticos]

100% USB activity confirmed with OSX pendrive?
Link LED flashing assures that...

"PP3V3_S0SW_LCD = 0V
PP3V3_S0SW_LCD = 0V"
Check for pulse at least in first seconds when board turns on.

 

[menatwork]

I Tried with a flash drive (OSX) and doesn't work (no flashing).

 

[2informaticos]

Do you get PPVCCCPU_S0G voltage?
PLT_RST_L goes hjgh?

There should be some history fault.
No reason to search for image, if no USB activity confirmed...

 

[menatwork]

PPVCCCPU_S0G = 0.7V and goes 1.5V after 10Sec and Comeback to 0.7V
PLT_RST_L = 0.65V

 

[2informaticos]

Board cannot work with platform reset enabled!

Check CPU_VCCST_PWRGD_R, PM_SYSRST_L and PM_PGOOD_CPUVCC.

 

[menatwork]

cpu_vccst_pwrgd_r = 0.99v
pm_sysrst_l = 3.3v
pm_pgood_cpuvcc = 3.3v

 

[2informaticos]

All look good.
Check also PM_PCH_PWROK, PM_PCH_SYS_PWROK and PM_SYSRST_L.

 

[menatwork]

Pm_pch_pwrok = 3.2v
pm_pch_sys_pwrok = 3.2
pm_sysrst_l = 3.2v

 

[2informaticos]

"PLT_RST_L = 0.65V"
Are you sure about this?
Because VCORE looks like board boots...

 

[menatwork]

Plt_rst_l = 3.3v

 

[2informaticos]

Try known good working BIOS.

 

[null]

@informaticos, I tried and still.
I will re-program the bios and see if works.
Any hint?

 

[null]

Try known good working BIOS.

Bios Re-program and still not working.
I Got all the rails, but no external/internal video.

 

[2informaticos]

If you cannot confirm USB activity, do not expect video.
Can be CPU, ot RAM problem, if BIOS is good.
Or just a corroded resistor...

 

[null]

No USB activity at all.