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820-4924 No Backlight PPVOUT_S0_LCDBKLT - 48V

A

aplas

New member
820-4924 No Backlight (in very rare cases it's present like 1 time of 20)
PPVOUT_S0_LCDBKLT - 48V (on pin1 of J8300)
BKLT_SCL - 5V
BKLT_SDA - 5V

Tested with 3 displays.
replaced LVDS connector.
replaced U7700.
tested resistors on BKLT_SCL and BKLT_SDA - good.

I'll appriacate any solutions to test, thanks.
 
2informaticos

2informaticos

Administrator
Staff member
Looks too high.
Did you try compatible full LCD assembly (including video cable)?
Try with broken screen, is more easy to detect backlight presence.

Do you really get image on internal LCD?
eDP data lines problem can keep screen black.
 
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aplas

New member
two lcd are broken, but backlight working and tested on other board:/ (they still includes cable)
Every startup I see apple logo with the lamp.
 
2informaticos

2informaticos

Administrator
Staff member
Do you get 48V at pin 1 of J8300?
If yes, change LCD connector.

Compare voltage with an working board; should be aprox 39V, I think.
 
A

aplas

New member
Usually I get 38/39V at pin1 of J8300 lcd connector with working backlight on other macbooks LP8548 driver series. I?ve already replaced the lcd connector. Maybe it?s something small I?m missing:(
 
A

aplas

New member
Thanks JohnB8812! I checked the screens I was testing and all of then were 2013/14. Even customer's screen on 2015 macbook pro was from 2013/14. That was tricky. Got another macbook pro 2015 and that screen worled just fine.
Is there any solutions to make 2013/14 screen to make working on 2015 board?
 
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