820-00165 (Intermittent back light)

[KC Micro Tronix]

I have seen this on a few boards now. Intermittent back light. I have one on the bench now.
My plan is to just shotgun but wondered what others have done about this.

When it fails the LED voltage is 17-20v and is slowly fading away.

Has anyone else fought this one?

 

[2informaticos]

Maybe bad LCD connector.
Did you try known good LCD assembly?
Check XW7720 integrity.
Could also be bad solders at LP8550; especially FB ball.

 

[KC Micro Tronix]

The intermittent is't physical. I tested on bench with my known good display. It worked. Installed board and it didn't. Tested again on bench and it didn't work. Then it worked.
LP8550 looked good "perfect" looking under it. I checked all the sides with the scope. There is no water damage on the back side of the board. Via is good no corrosion damage.

 

[2informaticos]

Change LP8550 and test again.

 

[JohnB8812]

Could be bad driver. Also make sure SMC_LID isn?t getting messed up by a corroded DC-in board/ cable