820-3662 no keyboard backlight.

BCN_Techs

Member
Hi,

Water damaged mac.

PPVOUT_S0_KBDBKLT 5V


BUt i compared with good working and see that BKLT_KEYB1 and BKLT_KEYB2 goes to 6-7 Volts when cover sensor near camera on display. But on this one it stais 0. Macos activated up down option for keyboard light control but there is no light.


Already tried to change U7701 but same result

Any help?
 

2informaticos

Administrator
Staff member
ALS from webcam is working?
KB control keys get disabled if you put flashlight on the webcam area directly?
 

2informaticos

Administrator
Staff member
KB and LCD backlight have both similar concept, based on boost-converter.
LCD has 6 return lines (BKL_ISEN_1-6) and KB only two (BKLT_KEYB1/2).
What voltages do you get at D7720?
 

BCN_Techs

Member
Got new keyboard backlight sheet. Still not working. Checked backlight sheet on other machine and it works.

What else i can check?
 

BCN_Techs

Member
Q7701:
Pin 5 12V
Pin 4 - 2,7V
Pin 1-3 - 0V

It is BKL_SW . Is that normal? Must change q7701?


Also checked XW7720 and there is continuity
 
Last edited:

2informaticos

Administrator
Staff member
I asked if D7720 is shorted; between its pins, of course.
How could I asked you about a short to ground if you already said to have 5V there???

"It is BKL_SW . Is that normal? Must change q7701?"
Why do you insist with LCD backlight???
I supposed you only miss KB backlight...

Check R7723/24/41/47.
Any voltage at C7747?
Also check connections between J4915 and KB backlight circuit.
 

BCN_Techs

Member
Ok. D7720 not shorted between pins.

Yes, Only miss keyboard backlight. LCD is ok.


R7741 is ok (32O Khms)

R7724/23 are 0.5 instead of 10 Ohms. But i measered on other board and it is also 0.3-0.5 so i think it is ok?

R7747 - 0.2 Ohms


C7747 has 0.8V
 
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