sekidata
Member
This A2289 2020 Pro came in with widespread liquid damage, including the trackpad connector, USB ports, and backlight circuitry. After cleaning, connector replacement, reflow, and DFU Restore, the machine starts up and produces an image but without display backlight.
I replaced the driver U8400 and the resistor R8400. Notably, the keyboard backlight boosts fine to 38V.
I get 12V on LCDBKLT_EN_L, which is too high to enable Q8400. When I pull BKLT_SD to ground, Q8400 turns on but PPVOUT_S0_LCDBKLT remains at 12.6V (no boosting).
I can’t figure out why the backlight driver does not boost. What are the conditions that prevent the backlight driver from activating?
I replaced the driver U8400 and the resistor R8400. Notably, the keyboard backlight boosts fine to 38V.
I get 12V on LCDBKLT_EN_L, which is too high to enable Q8400. When I pull BKLT_SD to ground, Q8400 turns on but PPVOUT_S0_LCDBKLT remains at 12.6V (no boosting).
I can’t figure out why the backlight driver does not boost. What are the conditions that prevent the backlight driver from activating?
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