820-01521 no image / no backlight

[KC Micro Tronix]

The board powers on. The PP3V3_S0SW_LCD will flash 3.3v only for a moment 1/2 sec and then it goes away.
I have traced this back to the EDP_PANEL_PWR_EN signal which also only flashes on for a split second.

Comparing against my test board this should stay on even with a panel not connected for some time.
I diode checked the data lines to the CPU and did not find any damaged lines.

I am really lost here.

Board enters S0 state. Appears to turn on.

 

[2informaticos]

Did you check USB activity and external video?
Do you note pulse at DP_INT_HPD and 5V_S0SW_LCD at same time?

 

[KC Micro Tronix]

no data activity at DP_INT_HPD
external USB drive does light up

 

[2informaticos]

DP_INT_HPD must be checked for DC level; there is no data.
But can only appear when 3V3_S0SW_LCD is present.
That's the reason I said to check for pulse.

USB drive activity LED flashes, or gets steady (power) light only???

 

[KC Micro Tronix]

not even a twitch on the scope.
light only.

 

[2informaticos]

Then the board gets stuck, not really boots.
There is not just a video issue.

Did you try DFU?