820-3330B A1286 No İmage


There is sound but there isn't video. On 3rd and 4th legs of J9000, there were short circuits, I cleaned them and made another path. On 4th leg there is 3.3 volts but there isn't any on 2nd & 3rd. So, I backtracked and checked U9000. On its 2nd & 3rd legs, there are 3.3 volts but there is no voltage on lcd_pwr_en. On the same path there is no voltage on first leg of R9678. In this case, should I replace U9000?


Staff member
No matter problem found on 820-3330 board, you need to resolder U8900 with leaded solder.
Is a preventive measure, which can also be related with your particular problem.

Do you get external video?

Check R9010/11, their traces and solders.
Post voltage and diode mode to ground at CLK/DATA lines.
Be sure video connector and cable are good; test with another LCD assembly.

BTW, use "pin" instead of "leg" for electronic components...


Staff member
Does that mod survive to PRAM reset?

PCH needs to talk first with LCD through DDC bus, via U9270.
Check if that MUX chip is correctly controlled.