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Apple A Day
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Backlight switching off at certain positions of the lid.

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Hello all,

I have a 2008 MacBook Core2Duo A1181 White 2.4 GHz. My backlight seems to switch off at certain positions of the lid. It started off with a very narrow range and within a few days it is switching off at much wider angle. However, the weird thing is that the range of "backlight off" is changing every day.

I have already tried a SMC reset and a NVRAM/PRAM reset and it did not help.

Based on further research I have concluded that it is quite likely a case of the cable connecting the main logic board to the LCD going defective. It works fine on an external display.

However, before I order a part, I want to make sure it is the right one. Plugging my serial number on to some websites have made me believe I have a Penryn core.

Now, if I want to try replacing the cable connecting the LCD to the MLB, which of these two should I get:

  1. MacBook Display Data Cable
  2. MacBook Santa Rosa/Penryn Inverter Cable

Which of these two is the one that passes through the left hinge and hence has a higher likelihood of being damaged from normal use? The macbook had never been dropped, but have been used for thousands of hours and has been opened and closed thousands of times.

And, finally, is there a chance it could actually be the inverter board which might be malfunctioning? If so, is there a way to find out if it actually is?

TIA.

Edited by: Sam Lionheart ( ) , Apple A Day ( )

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rdklinc
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You need an inverter cable, not a video cable, if you see a faint image and the backlight goes out when you flex the hinge. The inverter system (screen, inverter cable, inverter, board) is responsible for the light. You're lucky you have a 2.4GHZ, because that is the only speed machine that it is possible to determine the correct inverter cable for without further examination of the board -- you need the "Santa Rosa/Penryn" inverter cable you list above. This has a 3-wall connector on the logic board side, whereas earlier A1181 boards have a 4-wall connector.

In some cases you take off the topcase and open the hinge, and alleviate the stress point which was causing the cable to be crimped, and then save yourself buying a new cable, but in most cases you'll need a new cable.

There's a slight chance your screen is going out, but given what you've described, the inverter cable is the most likely culprit.

Edited by: rdklinc ( )

Thanks. Yes, I can indeed see a faint image when the backlight goes out. I will order the same then. Also, is this the right guide to follow? http://www.ifixit.com/Guide/Installing+M... Or is there a quicker/easier method? TIA.

Apple A Day,

Personally I take off the topcase, remove the screen bezel, and then pry out the hinge cover with a screwdriver, without removing the screen assembly or the optical drive. This gives you easy access to the inverter cable. Keep in mind though, taking this shortcut is a bit reckless and often causes some slight damage to the clips on the inside of the hinge cover, which is not fatal, but which can contribute to a small gap in the hinge cover on the backside of the machine. If you want to do the procedure 100% damage-free, follow the guide.

rdklinc,

I tried the full method today without a spare cable, just to see if repositioning the inverter cable might solve the issue. I untwisted the inverter cable, cut off the rubber flap on the cable, rerouted it to the other side of the hinge and and replugged it. I booted up and now the backlight is going off only in "some" positions! Does this confirm the diagnosis of the inverter cable being faulty as opposed to the inverter itself? Also, could you elaborate on your method a little? You take off the top case, remove the LCD bezel and before you take off the hinge cover, which screws do you remove? Thanks again.

Apple A Day,

It's most likely the cable. The inverter almost never goes bad (despite the popular opinion of people who think they have something to say yet have never actually repaired laptops). There is a greater chance that the screen is going out than the inverter itself, and a far greater chance that the cable is going out than the screen. To take off the hinge cover, remove the screen bezel, then take the three screws out of the hinge cover, then you can pry up the hinge cover with a flathead screwdriver, without taking the screen assembly off the computer. Just be careful, and be aware that one or two of the plastic clips inside the hinge cover will most likely be smashed/broken off.

rdklinc,

Agreed, the Invert is not the first thing unless the system got wet or banged.

Dan,

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Dan
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Have you tried shining a flashlight through the rear Apple logo when the screen is black? If the display LED backlighting system is at fault you should see a faint image of your desktop (what ever is currently displayed).

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