I've done a few no backlights on Airs, but I have never done an older style Pro, so I wanna make sure I get on the right track. I tried a PRAM reset to begin with, but no go. There is no sign of liquid damage anywhere on the board it looks as clean as can be (too clean actually). Took the board out tried a known good 2012 LCD and got nothing, so I started measuring. PPVOUT_SW_LCDBKLT in diode mode is 0.31 but fluctuates quite a bit. Is it something obvious like a feedback via, or LED driver for sure, or something obvious with that value? I just don't want to remove things like a moron but rather start on the right track and learn something. Any ideas?
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[SOLVED]820-3115 no backlight
- Thread starter JohnB8812
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Ok so measured voltage on PPVOUT_SW_LCDBKLT: When you first plug in the charger, the voltage starts at 1 volt and drops. Checked the fuse, 12.56 volts on the PPBUS_G3H side, and zero volts on the other so I would assume it's ok? Checked Q9706 on pins 3 and 4: Pin 4 was 0 volts, pin 3 was 0 volts. R9788 measuring normal same as C9782, R9789 measuring normal.
Checked resistance with LCD plugged in and all power removed and compared it to a working 820-3115 we have in the store for sale, and all of the values came back nearly identical. I'm pretty sure it's good but did warn customer of the screen. I think we can consider this case closed thank you for all the help Duke I'm very grateful for it.
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