[SOLVED]820-00165 Backlight Issues

[iambehr]

This macbook had a short in the board neard d7701, and the backlight driver feedback line was burned away.

I drilled a hole until the short to ground was gone, replaced the fuse and backlight driver, and ran a wire to replace the LCDBKL_FB line to the backlight driver.

Backlight works, laptop boots, and the fuse does not blow. However, the backlight no longer adjusts normally. Flickers between settings instead of fading, and the backlight turns off halfway down the on screen display's scale.

Any thoughts? Crappy backlight driver soldering? Or BKL_PWM issue?

Thanks.

 

[dukefawks]

Probably a broken trace/resistor/soldering to FSET, ISET or FILTER pins. Measure on diode mode the resistors connecting to them to see if they have continuity to the LP8550.

 

[iambehr]

Resistors and traces were intact! Incorrectly soldered LP8550 chip. Backlight now works normally.
I suspect I pushed on the chip while the solder was still liquid, under the microscope the chip was slightly tilted and the balls were flattened.

Thank you for the clue.