820-01814 no image

[2informaticos]

Any history available?
External video?

 

[thomamagic]

the machine worked perfectly. The customer wanted to restore the system, everything went well, he turned it off normally and put it away. then 1 week later he wanted to turn it back on, no more signs of life. he changed the battery and the same thing
At that moment he decides to bring it to us and we notice a short circuit onPPBUS_G3H
we have remove bad caps after inject voltage 1v en this
Fan start, caps lock led ok but no sound when start.
I dont have signal in external with usb-c hdmi adapter

 

[2informaticos]

I can't find C4606 in schematic...

 

[thomamagic]

Oh sorry, it's C6406

 

[2informaticos]

Did you find any corrosion sign around U6400, or other area?

 

[thomamagic]

No corrosion, no liquid on all mainboard

 

[2informaticos]

If Caps Lock LED reacts, strange to miss USB activity and external video.
Check if machine goes into target disk mode at least.

 

[thomamagic]

yes very strange
i enter correct in dfu and restore correct
I start in target mode when push T button but not recognisez with the second machine

 

[thomamagic]

think no image in external because os is not installed after dfu test

 

[thomamagic]

i can test remove U6400 for test without?

 

[2informaticos]

You should get external video, if internal LCD is disconnected; no matters if macOS installed, or not.

U6400 can be removed, but I doubt to be the culprit, if no corrosion there.

 

[thomamagic]

check with lcd disconnected and same
U6400 removed but same problem too

 

[thomamagic]

?

 

[2informaticos]

Check diode mode to ground at EDP_INT lines (J8500).