00163 No Backlight

[BrickBreaker]

This was sent in with liquid damage. I have 5v on the LCD detection filter, 5v in to the backlight driver, BKLT enable present, continuity along all these backlight traces, the voltage divider for the first transistor isn't being shorted by the driver. If I manually short it, I get 12V on the backlight because driver is still not telling the second transistor to switch power on the coil. I am stumped. LCD is definitely the right year, done NVRAM reset everytime and I see flashing folder with a flashlight. Replaced driver multiple times including at the same time as the mosfets. Using new drivers everytime from the same batch so I tried a donor board no change. I2C lines to the connector are good now, had to replace the connector but diode mode looks good now. TIA!

[piernov]

Re: 00163 No Backlight

Current sensing resistor R7700 and traces to LED driver? VDDA and VDDP of the LED driver?
Feedback? I2C on the LED driver ok too?

[BrickBreaker]

Re: 00163 No Backlight

R7700 is good, continuity is there to the driver for current sensing. 5V on VDDA and VDDD of the driver. Feedback is good, I2C lines are good. If I manually short R7702 I get 12V on the otherside of Q7706, but it still isn't getting switched/boosted. Driver has everything it needs but isn't doing it's job.

[piernov]

Re: 00163 No Backlight

Soldering is good for sure?

[BrickBreaker]

Re: 00163 No Backlight

Yea just took another long hard look at my soldering. Also confirmed external video is working over thunderbolt.

[piernov]

Re: 00163 No Backlight

And SMC_LID high?

[BrickBreaker]

Re: 00163 No Backlight

Yes. SMC lid 3.4V lid works as intended when I boot up the board in the case with external (thunderbolt) display attached.

[piernov]

Re: 00163 No Backlight

Tried another display assembly?
I'm out of ideas. If everything external to the LED driver is ok then it should be the LED driver itself that's causing the issue.