Why does this A1398 MacBook Pro have no Backlight?

October 5, 2019

What's Wrong With This MacBook?

This customer sent in their MacBook Pro to our store in New York City for our logic board repair service because it has no backlight on the screen. It appears to have some liquid damage.

How can we fix the issue?

Initial Diagnosis

The first thing we do with this MacBook is measure the resistance to ground on the backlight circuit with and without the LCD connected. With the LCD connected, we get 24 ohms to ground. WIth the LCD disconnected, we still only get around 320 Ohms to ground. This means that there is an issue with both the screen or screen cable and the logic board.

Repairing the board

The first thing we do here to rule out any issues with the connection to the LCD is replace the LCD connector. We remove the old one and replace it with a brand new connector. After this, we measure the voltage on the backlight circuit with the screen connected. We measure this to be 46.5V, which is the proper voltage. This board should be showing a light on the screen, however we suspect that this is now an issue with the LCD cable, rather than the board. After replacing this cable and running the board through the Ultrasonic cleaner, it should be fully functional again.

I can't fix this myself. How do I get it fixed?

Rossmann Repair Group offers MacBook Logic Board Repair Services in New York City. Our MacBook Repair is not limited to Austin though, we accept mail-in repairs from virtually anywhere! Visit https://www.rossmanngroup.com/macbook-logic-board-repair/  to start your MacBook repair.



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