820-02020: No image or backlight on display

[repMacFixit]

I have a weird one. The board powers up but no image or backlight on the built in display. When connected to an external display, the external display comes on (black screen), but i can move the cursor into it. I tried using the key combo to switch the screens (command + F1, and command + Fn + F1) with no success. I unplugged the built in display to hopefully force the laptop to use the external, but have the same result as when the internal display was connected.
I performed restore successfully but still having the same issue. Note, when it boots up, it does make the apple booting chime. The caps lock light comes on when pressed also.

Also, the fan goes high and stays high.

Any suggestions

 

[2informaticos]

How the problem appeared?

Test external video closing the lid, once booted.
If still no image, check UR200 signals.

 

[repMacFixit]

The laptop was sent to me like this. No corrosion or liquid damage.

With lid closed, the video does switch to the external display.
Oh forgot to mention that i did buy a display and replaced with the same result.

 

[2informaticos]

Check JP600's voltages (internal LCD connected): pins 4, 6, 44, 45.