MacbookPro 14 820-02098 liquid damage internal LCD not working

[xdever]

Hello,

I have an A2442 MacBook with 820-02098 board. It had water damage, and some service already worked on the board and removed the HDMI connector.

When I got it, the machine worked fine, except for half of the keyboard, which needed to be replaced because it got liquid. The back side of the fans had some sticky liquid, so I guess the board had to have some at some point in the past as well, but it seems to be cleaned by the service who tried to repair it. There is no sign of any oxidation or trace of liquid on the board or the connectors. Everything is as clean as it can be. However, after a day of usage, the LCD just turned off. After closing and opening the lid, it was up and running happily again. And then, after about the 10th of such episode, it did not come back anymore. The time when it went off was not related to any movement, and it went away even when I was using it with an external keyboard and screen without moving the machine, and it did not turn off no matter how I moved the LCD. So I doubt that it is related to the flex cable.

The miniled backlight is working just fine. A dim, blurry picture can be seen through the dark LCD (video here: https://photos.app.goo.gl/ffV9X2uNAmz4DrNN9). Interestingly, immediately after opening the lid, if it has been off for long enough, a trace of a sharp picture appears: the menu bar is clearly recognizable. Then it immediately fades away. It takes time for this to happen again (~a hour). Otherwise, it is just dark. This fade-away effect indicated some kind of power supply failure, but the 3.3V is present (measured in the circuit with a wire soldered on pin 1 of RP700). With the LCD disconnected, I also measured that EDP_PANEL_1V8_EN is present. PP1V8_S2 is present, as the rest of the laptop works perfectly. I measured all the RC filters on the LPDP_INT_DATA* lines, they all seem to be good, no short to each other nor to the ground. I also applied lots of flux and resoldered these filters, even though no trace of oxidation was visible.

Does any of you have any idea what can cause such behavior and where to look next?

Thank you

[Sephir0th]

Re: MacbookPro 14 820-02098 liquid damage internal LCD not working

And not even one picture shared of the area in question...

However and honestly: I'm not into Apple devices but if the design here is similar or even the same like at all the other laptops then you're probably looking into the wrong direction. The LCD enable should be present since you can notice the picture. But the really important things to check is whether the main power rail (PPBUS_G3H or however it is called here) is present at the connector (also check diodes/fuses in this area) and whether the backlight enable also has voltages like expected.

[xdever]

Re: MacbookPro 14 820-02098 liquid damage internal LCD not working

And not even one picture shared of the area in question...

However and honestly: I'm not into Apple devices but if the design here is similar or even the same like at all the other laptops then you're probably looking into the wrong direction. The LCD enable should be present since you can notice the picture. But the really important things to check is whether the main power rail (PPBUS_G3H or however it is called here) is present at the connector (also check diodes/fuses in this area) and whether the backlight enable also has voltages like expected.

Since the service cleaned up the board, I don't know which picture to share. It looks like it comes straight out of the factory.

I checked the main 3V rail: with the LCD disconnected, it is present on the connector, and with the LCD connected, it is present on RP700, as I wrote. I don't see any way to measure this on the connector when the LCD is connected, as there is no way to access any of its pins.

As I said and the video shows, the backlight is present. Also, shining a strong light on the LCD doesn't show any picture, so I highly doubt that this has anything to do with the backlight.

[Sephir0th]

Re: MacbookPro 14 820-02098 liquid damage internal LCD not working

Sorry, then it was a misunderstood since for me it looks like you have picture but without backlight.
Visual inspection with microscope, checking for good values and resoldering of each component between the M1 CPU and the display connector advised. A summary of all voltages present at the connector would be nice if possible. Also a picture of how it looks like around the connector would be good before. In addition I'm interested in how it looks like at the direction of the removed HDMI board. I don't want to be the pessimist guy here but it can be you're dealing with a irreparable M1 damage here.

Ah and before I do forget: How is it with external display?