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An image comes up on the monitor but the screen is really dark and i cannot see anything. However, when i connect an external monitor everything works great. I opened up the machine and made a few observations the lcd connector cable does have a corner that looks burned or chipped. Could this be the problem? I figured that this wasn’t the issue since a picture still comes up on the screen, but idk… Does anyone know where the backlight fuses and other connected components are located on the motherboard of my machine? Ideally i need a schematic so i can probe my board and find the culprit. Help please and thank you.
The LCD cable has a number of parallel lines and “power rails.” 1/Some of there lines transfer data, and they are ok, which is why you are seeing something on the screen. 2/ Some lines transfer info about the board to the screen, and feedback from the screen. 3/ Some of the lines transfer power to light the screen, and because they are carrying a high voltage, they usually burn and corrode very quickly from liquid damage, and power stops being provided to the screen. The screen then stops from lighting up. We say it has “no backlight.” In your case, 2/ or 3/ or both may be bad. The power lines continue (backwards) from the LCD cable to the LCD connector, to the backlight circuit on the board which is basically a fuse, a backlight drive, a coil, a diode, a few caps and components, and the web of lines (traces) connecting them together. Any of the previously named components can be bad. Sometimes just one, sometimes all of them (although I am yet to see a bad coil and diode). So if the connector where the LCD cable is connected is indeed corroded, it is very easy to fix by a micro soldering tech who can proceed to test and determine if other parts of the backlight circuit as described above need fixing. But connector is always replaced first. If you want your board to last you some time, it should also undergo professional ultrasonic cleaning to stop and remove corrosion everywhere else on the board; also must replace all the small components that are corroded and prone to failure soon. All the above repair and refurbishing should cost about ½ the price of replacement board from Apple (which gives you a refurbished replacement board, not new) and with the same if not a better warranty. For example, Apple currently warranty their replacement refurbished (new is not an option you can request) boards for 90 days, we warranty our repairs for 180 days. Finally, the corrosion can extend from the connector to the LCD cable itself which may or may not be replaceable alone without replacing the screen. Replacing the screen will more than double the cost of repairing your laptop, so this must be addressed promptly. Thus my advice for you in the immediate is the following: 1/ Disconnect the battery, THEN disconnect the LCD cable and everything else from the board. 2/ Remove the board from the computer, clean it all with a soft tooth brush dipped in isopropyl alcohol at 90% or higher concentration. Insist on the LCD connector. 3/ Reassemble and test again, if you have backlight that’s good, but I would still have the board repaired (replace LCD connector if it has black pins and ultrasonic the board). If you still don’t have backlight and the screen light is still very dim, cover the tip of the cable with some kind of paper tape or kapton tape to isolate it and prevent it from shorting with something on the logic board. And use the laptop with an external monitor or TV until you can have the board repaired. Which should be earlier rather than later. Corrosion may still be taking its toll even though you cleaned it with alcohol. Don’t reconnect the LCD until the cause of the failure is known and repaired and preferably the connector replaced. You may inflict additional damage. If after cleaning, you don’t have backlight and want to take a shot at fixing it yourself, you need to find the board number, based on which you can find the schematics, based on which you can find the back-light circuit and troubleshoot it. But once you find an issue, are you equipped to perform soldering? If yes, you still need to start at the beginning: cleaning the board and replacing the connector if it has burnt pins.
