a2338 no backlight (i2c_bklt_sda, i2c_bklt_scl no signal)

[khj]

Hello.
I have a problem about backlight.
I changed almost backlight parts, but I can't get over 40v from them.

I think display connect signal is missing. (I2C_BKLT_SDA, I2C_BKLT_SCL is just pull-up voltage (5.18V) when I connected edp )
so backlight circuit doesn't step-up voltage.

normal logic board has I2C signal. but bad one is missing.

what should I do?

[mon2]

Be sure your display is compatible with this model of logic board.

what is the voltage to ground of the smbus scl and sda lines?

https://logi.wiki/index.php/Backlight_Troubleshooting

[khj]

Be sure your display is compatible with this model of logic board.

what is the voltage to ground of the smbus scl and sda lines?

https://logi.wiki/index.php/Backlight_Troubleshooting

yes I used display that working on normal board. in diode mode, them looks like 0.5

[mon2]

Diode mode confirms the i2c lines are not damaged.

confirm the pull up voltage is present. Check the lcd connector to be sure the led lines are all reaching the backlight controller.

remove all power. Check the resistance to ground of the backlight rail. Compare to good unit.