820-3330-B no backlight but PP3V3_SW_LCD, PP3V3_S0_DDC_LCD and PPVOUT_S0_LCDBKLT ok [FIXED]

[stef4n]

I'm working on a 820-3330-B; MacBook Pro does boot, there is a chime, and there is image, but no backlight.

I measured voltages on J9000.

I do have 3.308V on pins 2&3
I do have 40V on pins 38, always, but 0V on pin 39 (sometimes 30V) and 0V on pin 40. Probably a measurement issue, because 9 times out of 10 I get 0V, and 1 out of 10 a nice 40V on each pin
I do have 3.342V on pin 4, 6 and 7

I checked R9010 and R9011, they both are at 4.5kOhms
These two resistances read 100kOhms on another similar MacBook (which does not turn on)

Can it be an issue there ?

I tested with another screen : no backlight, but picture.

 

[2informaticos]

40V is a correct voltage for this 15" machine.
Try 2-3 times PRAM and SMC reset.

Check BKL_PWM voltage.

Pins 38-40 are connected directly on the board; not sure how can you get different voltage readings.
Just in case, change J9000.

 

[stef4n]

PRAM and SMC reset already tried;
BKL_PWM is at 2.500V, measured on C9704
I agree about pins 38-40, i should read the same value on each but most of the time (90%) I don't.

I will replace this J9000 tomorrow, and update this post after. Wanted to be sure I didn't miss anything obvious

Thanks

 

[stef4n]

J9000 was the culprit. Connector replaced.