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Does anyone know the use of the port on the top next to the power for the logic board? You plug a black cable in to it that connects to the display. When I connect this to my display it cuts the power. Does anyone know the use of this port?
Thanks
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If you are referring to the wide port that is next to the serial number, it is the LCD Function Interface. Problem symptoms related to this port would be no power to the LCD and no LCD backlight.
Is the Cinema Display showing in your computer's device tree?
Also, there are test points in the back of the logic board that can be used to verify proper power flow in the unit. If you would like that information please let me know and I'll post it.
So, this could also be a bad LCD function cable or a bad all-in-one cable. According to the documentation that I have, you should be able to read voltage on the USB ports just with the unit being plugged in and powered in. With the USB ports being dead, it points more likely to the all-in-one cable.
Several of the troubleshooting options for this issue seem to point to that as a likely candidate.
Causes of voltage issues can originate with a bad cable (especially if it has a direct short somewhere inside it), or bad fuses on the board, or problems with the power supply itself. The USB ports on the board should show voltage with the logic board receiving power and the unit turned on. Perhaps you can post a picture of the logic board and show which test points you are using? What are you using as your source for determining where the test points are located?
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No it is not showing in the device tree. I have tested the points and they all show the correct voltage. As soon as I plug in the black cable into the lcd I can see that the fan has stopped spinning. The usb ports on the back and microphone also don't work. Do the usb items only work when the screen is on? Thanks for your help.
I have used another usb cable with the same port and it still not listed.
Could there be something so it only works with a AIO cable?
Thanks for your help, This could be it
How is it that the voltages are not 0 when the usb cable is plugged in? Maybe a bad connection? It does sound really possible.
Thanks for your help
I have been using a techician guide
http://tim.id.au/laptops/apple/displays/...
On page 16 you can see some test points.
I have tried using a different cable but it still doesn't work.
So maybe the logic board?
Thanks for your help
So you have tried a different All-In-One cable?
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