820-01521 "no image"

[KC Micro Tronix]

I have a 820-01521 that came in for screen repair now it's on my desk. They replaced the LCD and the machine has no image.
all the rails are present on J8550 Both 5v and the 3.3v are present. Back light is not but I'm not surprised with no image. It does not get that far.

How do I determine of the CPU is damaged in cases like this?

 

[2informaticos]

I think you talk about J8500.
If voltages are ther, DP_INT_HPD should also be present; check that anyway.
This signal is required by PCH to recognize the LCD panel.
Compare diode mode readings on all video lines with good MLB.
Check values w/ and w/o LCD connected.