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LED Backlight is off and Flashing Questionmark after IceTea accident?

I bought a MacBook A1342 on eBay with a Tea-Accident in the auction description.

First I opened it up through the step-by-step Guide and cleaned it up anything inside. It was already dry, but I cleaned the sugar which remained there.

Then I reassembled it.

Now the following is happening:

After power-on through the powerbutton I can hear the startup chime. The screen keeps dark. But a short time later I can see a flashing questionmark in the middle of the screen - light from a lamp through the backside of the (apple-logo) screen.

Because of sugarremains at the lvds-connector, I presume the part on the logic board controlling the LED-Backlight could be gone defective by the IceTea.

How can I test the LED-Backlight without changing the whole display or the complete Motherboard (logic board)?

Can I measure anywhere at the lvds out? Or at a measuring point in front of the lvds out?

Or do you have a pinout of the lvds connection?

Many thanks for your Support...

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Many Thanks for your help, so long.

Now I've tested the mini-display port to dvi. The port did not turn the external monitor out of the standby mode.

By inspecting the lvds cable I saw 3 defective pins at the cable. Does anyone know the exact description of the connector at the cable?

At the moment I'm stuck in a point to be hopeless.

Can somebody help me further.


Yesterday I tested the MacBook with an external DVD-Drive. I was wondering the Snow Leo Install Disc started without any Problems and the Installation finished successfully. After a reboot it started from HDD. Now I know theres something bad with the internal Superdrive.


I have the same problem you found the solution to turn the LED Backlight screen please tell me


Please start a new question


my problem is that the LEDs do not light up the screen anyone know how to bypass the LVDS cable


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You can hook the computer to a external monitor and see if you have video there. If so that would possibly eliminate the logic board but there is one step left. The flashing question mark means it can't find a bootable drive. Did the seller remove the hard drive before selling the computer? If there is a drive in the computer you need to confirm the drives connection to the computer is clean and solid. If there is a drive and the connections good you need to try and load an operating system. I would recommend Snow Leopard as the least expensive and suitable for your computer. Once you have the rest of the computer working with the external monitor you can look at the LCD problem.I would look at the cable first, the backlight second and the LCD last. A lot of work ahead for you--use the ifixit step-by-step guides and repair one thing at a time. Good luck. Ralph

MacBook Unibody A1342

MacBook Unibody Model A1342 Teardown

One last thing--if the computer failed the first step (external monitor) your logic board is probably bad. Ralph

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Thanks for your reply. The seller didn't remove the drive before selling.

The connection between HDD and logic board seems to be OK.

I also tested the RAM and the RAM slots, they seem to work properly.

I tried to boot from the Snow Leo Install Disc, but the Optical Drive spins a littlebit, pauses, spins a second time and after this the disc is thrown out.

Tomorrow I will borrow a mini-display-port to HDMI from a colleague to test the video out.



+ excellent advice


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When you can see a faint image then the LVDS part is probably alright. Missing Backlight is an issue with the inverter or the inverter cable. Check these first.

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Thanks for your answer. Does a Display with LED-Backlight need to have an inverter? I thought it's only needed by the CFFL-Backlight?!

Please correct me if I'm wrong.


You're right, a led display doesn't need an inverter, so look at the power supply for the backlight instead.


Does anyone know which pin of the display cable responds to the LED-Backlight? Or isn't it possible to bridge the lvds-connector from a point anywhere on the logic board to operate with the correct voltage? Does anyone know the correct voltage to operate with the LED-Backlight?

Could this be possible?


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