vinaypundith
New member
Hello,
I have a 2019 16" MacBook Pro (A2141) with no LCD backlight (the laptop does power on, boot to macOS and display stuff on the screen, but the backlight is off so you have to shine a light at the screen to see anything).
I tested the PPVOUT_S0_LCDBKLT line at the terminals of L8452 and CC786 while the laptop was running, got 0 volts (while the corresponding points on a working A1707 unit I tested were at 50-ish)
With the motherboard removed, I'm getting 55 to 56 ohms resistance between any point on PPVOUT_S0_LCDBKLT and ground (a screw hole).
So what I'd like to know is:
- Does that resistance indicate a "short to ground" on the PPVOUT_S0_LCDBKLT line? A working A1707 board I tested is an open circuit between that line and ground.
- If it is a short to ground, how would I find which component is causing it?
- Where is this power line generated, what chip/component, and from what source power line? I can't seem to find it on my schematic or boardview.
- If it is not a short to ground, what do I test?
Thanks!
I have a 2019 16" MacBook Pro (A2141) with no LCD backlight (the laptop does power on, boot to macOS and display stuff on the screen, but the backlight is off so you have to shine a light at the screen to see anything).
I tested the PPVOUT_S0_LCDBKLT line at the terminals of L8452 and CC786 while the laptop was running, got 0 volts (while the corresponding points on a working A1707 unit I tested were at 50-ish)
With the motherboard removed, I'm getting 55 to 56 ohms resistance between any point on PPVOUT_S0_LCDBKLT and ground (a screw hole).
So what I'd like to know is:
- Does that resistance indicate a "short to ground" on the PPVOUT_S0_LCDBKLT line? A working A1707 board I tested is an open circuit between that line and ground.
- If it is a short to ground, how would I find which component is causing it?
- Where is this power line generated, what chip/component, and from what source power line? I can't seem to find it on my schematic or boardview.
- If it is not a short to ground, what do I test?
Thanks!