Macbook A1502-4924, Boots with Backlight but no image.

[rotceh_dnih]

Hi all!

Need a hand on one that's been doing my head in..

A1502 4924 come in water damaged after being "in a cyclone". was still dripping wet with slight corrosion all over when i got it, trackpad connector & u8160 being the worse hit. threw the board in the ultrasonic and let the rest dry out on a lcd hotplate all looked good so i threw it together and it boots , has backlight 38V, chimes and loads into macos fine but no image on the lcd.

HDMI out is working fine with lvds unplugged.

J8300 pins

1 - 38v
3 - 5v
4 - 3.3v with drops ie looks like its talking.
5 - 3.3v
9 - 3v
28,29,30 - 5v

checked FL8300 - 8303 has connection and looks correct.

tested board in known good deck/lcd but no joy.. i haven't put my board in his deck yet so i'll do that and update but not sure what to check next any help will be hugely appreciated!

[mon2]

Re: Macbook A1502-4924, Boots with Backlight but no image.

Both pins 3 & 4 on J8300 should show activity for the eDP display panel.

Remove all power. Meter in resistance mode.

Check the resistance to ground for

pin 3 (J8300) - reading ?

pin 4 (J8300) - reading ?

Then confirm that the I2C_BKLT_SCL is able to make it back to other locations on the logic board (ie. R7750). Then again for I2C_BKLT_SDA and R7751.

What are the details of pins 6 & 7 of J8300 ?

Check the presence of each LVDS cap as per attached. They must be present to drive the LVDS signals onto the target display panel.

[rotceh_dnih]

Re: Macbook A1502-4924, Boots with Backlight but no image.

Thanks mate

black prob on ground with meter in auto ranging power indeed disconnected for ohm readings
pin 3 (J8300) - 42k - 5v
pin 4 (J8300) - 42k - 5v

continuity from J8300 -> U7700 for both SCL&SDA, R7750-7753 are correct resistance

pin 6 (J8300) - 1MOhm - 3.3v
pin 7 (J8300) - 1MOhm - 3.3v

C8320-8327 are there.

[rotceh_dnih]

Re: Macbook A1502-4924, Boots with Backlight but no image.

Update..

Twas the bloody lcd on the customer deck .. swapped into my known good and it fires up as expected.

ALWAYS TEST WITH KNOWN GOOD PARTS!!!!!