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A1398 820-3787

I

iFix

Member
Hi.

I have this A1398 with no backlight issue. The initial problem was Q7706, I replaced it and got all voltages but no backlight I had output on PPVOUT_S0_LCDBKLT. the output voltages are coming and going as they like :) SCL and SDA lines are almost 5v and diode mode is good on all components. I checked all resistors and they are measuring good values. I also replaced Q7701. Ideas?
 
I

iFix

Member
I opened the top side of the lcd and found liquid damage on the lcd flex and connector. I replaced the connector on the lcd itself and the flex cable it flashed 2 times when on power and now i lost PPVOUT_S0_LCDBKLT. I'll recheck the circuit again
 
I

iFix

Member
I reconnected all and i got PPVOUT_S0_LCDBKLT on the lcd side, but it just flashed and no backlight
 
I

iFix

Member
When I get the 50v they are stable, but not every time I get them. When I don't get 50v to LCD , also I don't have PPBUS_SW_BKL output from Q7706
 
I

iFix

Member
Weird but it started working. I just connected the KB and it showed a backlight on the lcd it has been working since then. I will test it for some time, but it look great. We can close this thread Solved :)
 
I

iFix

Member
Morning. You were right 50v it's too high. after some time testing, it lost backlight again and it gets all voltages to the lcd connector on the lcd side. LCD backlight strip replacement next step?
 
I

iFix

Member
I've done led strip replacement and LCD only many times it's not an issue. I will open it inside maybe even the strip has liquid on it. I don't have another 2012/13 lcd assembly to try, only 2015 but they have different signals
 
I

iFix

Member
Hi. Going back to this one. I got another LCD new for testing and still no backlight.

PP5VR3V3_SW_LCD - 5V
PPVOUT_S0_LCDBKLT - 54v
PPBUS_S0_LCDBKLT_PWR_SW is 11.4 and 0v on BKL_SW coming from U7701 to Q7701, not sure how it should be...
 
I

iFix

Member
Could it be that the lvds connector is making the issue since the LCD and lcd flex are new and all other stuff seem fine...
 
I

iFix

Member
I have 54v from D7701 pin 2 toward the LCD connector and on the connector itself. With the old LCD, I also got on the lcd side same
 
I

iFix

Member
The old lcd was partially broken and i left it like that, but shows same with the new one. I'll check the resistor and revert
 
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