820-3662 no keyboard backlight.

[BCN_Techs]

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]

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

 

[BCN_Techs]

Yeah, it is disabled when cover sensor, so it seems to work

 

[2informaticos]

Try known good keyboard backlight.

 

[BCN_Techs]

Bought it yesterday, in couple of days will try.

but what exactly generate this line BKLT_KEYB1?

 

[2informaticos]

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]

D7720 get 5V on both points.

 

[2informaticos]

If D7720 is not shorted, try another keyboard backlight sheet...

 

[BCN_Techs]

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

What else i can check?

 

[2informaticos]

D7720 not shorted for sure?

 

[BCN_Techs]

Yes. 5V on both ends. And no short there

 

[BCN_Techs]

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

 

[2informaticos]

0.8V is too low.
Do 2-3 PRAM resets and test again.

R7741 must be 32K aprox, not 320K.

 

[BCN_Techs]

its 32 Kohm, i put O near 32.


Done PRAM no result, Also done SMC RESET and NVRAM Reset. Same result.

 

[2informaticos]

Do you really think that I said to short the pads to ground???