820-00165 no image and no backlight

[Alex97Lewis]

Got a bit of an issue with this board, no known liquid damage but had a damaged J8300 and have replaced. Noticed C8325 and C8324 were removed from the board so replaced those - but now I'm getting no image and no backlight.

I've measured the following which should help.

Q7707:
2- 3.3v
3- 8v
4, 5 and 6 - 0v

From this have noticed pin 5 of Q7707 is linked with R1430, checked resistance and got 99.8K. Is pin 5 meant to be the same as pin 2 to open the gate?

Q7706
Pin 3 and 4 - 8.2v
All other pins are 0v

Diode mode of L7701 shows 390 on either side, D7701 shows 390 on pin 1 and 590 on pin 2.

Any assistance on this would be much appreciated.

Edit: I know this screen is a good working screen as I've been using it on multiple boards for testing and it displays fine.

 

[2informaticos]

You said no image AND no backlight.
Image MUST appear first; why did you fix on backlight?

"4, 5 and 6 - 0v"
You cannot expect backlight when missing EDP_BKLT_EN.

Did you check for USB activity?

 

[Alex97Lewis]

If I remember correctly, I did check to see if there was USB activity and I think there was. I can't check until Monday now though, and yeah I understand pin 5 being 0v shows there is no backlight and thats why I checked with R1430 to see if that was damaged in any way. If I'm looking at the schematics correctly, EDP_BKLT_EN gets created by the CPU/PCH?

How would I go ahead and test the image related issues as I'm not getting any image even from shining a torch behind the apple logo on the lid, nothing at all. CPU gets hot to the touch with heatsink off and pulls roughly 0.8A making me think it's booting up.

But as stated I can definitely confirm this isn't a bad screen as it works on every board I've got working.

 

[2informaticos]

Pins 18/19 of J8300 MUST get 3V, at least in the first few seconds (when chime).
This voltage is not maintained, if pin 14 doesn't go high in the same time.