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Question: Backlight turns on and off randomly


I have an extremely annoying issue with my original 13" MacBook. Basically, at random times the backlight shuts offs as if the computer is going to sleep. Sometimes, it can be fixed (temporary) by shutting the lid and opening it again, as if the computer is waking up from sleep. There seems to be no obvious way to reproduce this problem – sometimes I go for an hour or more without it, sometimes it happens ever 10 seconds and the computer is unusable.

So far, I've tried resetting the PRAM and the SMC – no effect.

Any ideas to fix this would be greatly appreciated.

Macbook (late 2006), Mac OS X (10.6.4)

Posted on Jul 28, 2010 4:42 PM


Jul 28, 2010 6:27 PM in response to rhombus In response to rhombus

Could be from a bad connection between the MLB and the display. The MLB (main logic board) and integrated graphics may be going bad. Or your backlight may be going out.

Does this happen when you tilt the screen back and forth?
Any vertical or horizontal lines appearing at any time?

Jul 28, 2010 6:27 PM

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Aug 4, 2010 3:30 PM in response to sirfaba In response to sirfaba

I'm also having this issue... Tried all sort of resetting and looking at my power options but nothing out of the ordinary. I don't get any horizontal lines, or distortion when moving the display and it goes off at random times and can only be relit by coming out of sleep.

One thing in particular that was quite weird about it... I have the screen connected to an external monitor most of the time because of this issue in clamshell mode. I unplugged the external and the internal screen momentarily came on and then went to turning off. (well the backlight) When I plugged the external back it, it didn't effect the internal monitor until I selected mirror displays and then it came back on straight away.

I hope someone understood that.

I'm now at the last resort of reinstalling the OS - but don't really want the hassle of doing that in case anyone else has any ideas.

Aug 4, 2010 3:30 PM

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Aug 20, 2010 11:34 AM in response to markbrooke In response to markbrooke

sounds like bad inverter board for the LCD's fluorescent backlight

if out of warranty, you can remove plastic piece between hinges, buy an inverter board on ebay for typically <$20, and DIY. basically unplug wires from both ends of existing board, slide in new board, reconnect cables.

i did so 2+yrs ago, still going strong.

Aug 20, 2010 11:34 AM

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Aug 31, 2010 3:40 PM in response to GTR In response to GTR

Yeah I'm really far out of warranty. I tried replacing the inverter but the problem is still there. (I think the inverter I brought off eBay might be 2nd hand... could I be really unlucky and have brought a broken one??)

Still yet to find out exactly when it is happening... It can stay on for hours and then turn off and on multiple times in a short time. I normally keep it on the 2nd to lowest brightness setting, and when the screen goes off, I just turn the brightness all the way down and back up again and it comes back on. Sometimes when putting the brightness back up it immediately goes off then on again. I don't see flickering at any other times though, it just immediately goes off so I don't think its a bulb problem. Pressing on the chassis around where the connectors are doesn't cut anything out and neither does moving the laptop or screen.

I've also ran apple hardware tests and tech tool hardware scans both finding no problems. (Not that I know they can test for inverter or bulb problems)

I've done a fresh reformat as-well not from a time machine backup to no avail!
Is it possible it could be power related because my battery is in the 'replace now' stage? But the problem happens on power as-well.

Aug 31, 2010 3:40 PM

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Oct 28, 2010 6:14 AM in response to markbrooke In response to markbrooke

I have the exact same situation, I also use the adjust brigthness to 0 and the back up to get the light back on but sometimes it keeps going off in less than a second several times and it gets really annoying. Have you found any solutions? Did you try replacing the inverter board again?


Oct 28, 2010 6:14 AM

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Nov 16, 2010 1:29 PM in response to santi p In response to santi p

literally the SAME issue as above. Backlight is fidgety at best. Ive re-installed the OS (10.5.2) and did the updates and reset the power management. The, only difference between pre OS reinstall and post OS reinstall is now the backlight will go off if the screen is moved from a certain position. Does anyone have an update and also a credible link for a diy inverter install?

Nov 16, 2010 1:29 PM

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Dec 1, 2010 8:49 AM in response to jekyll1489 In response to jekyll1489

I am having the exact same problem as markbrooke and santi p. When waking the computer from sleep the backlight goes on and immediately off (the screen itself stays on). If I adjust the brightness to 0 and then up it works again, but only until it randomly goes off again.
This is totally independent of tilting the screen (also my battery health is at 92% so it shouldn't have anything to do with that).

Does anyone have any advice on how to fix this problem? That would be great!

Dec 1, 2010 8:49 AM

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Dec 22, 2010 9:19 AM in response to Encarsia perplexa In response to Encarsia perplexa

Mine has started having issues as well. When it boots the display is fine, but once I plug it to an external monitor and close the lid, it will no longer "wake" up on board video. The Apple logo also stays dark. I have to reboot to get internal video back.
External video is fine.

Dec 22, 2010 9:19 AM

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Dec 22, 2010 11:15 AM in response to beacon126 In response to beacon126

mine started doing the same irritating backlight issue today. it began while i was listening to a radio station and trying to blog. i rebooted with variable success. what has the concensus fix been? i hate to take the time, but going to the genius bar might become necessary, if it persists.

Dec 22, 2010 11:15 AM

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Dec 31, 2010 4:58 PM in response to dragonsdaddy 53 In response to dragonsdaddy 53

Having a similar issue to some of those described previously. Backlight started flickering on and off randomly. Then I discovered that if brightness was kept at 3 or more increments below max, all was well. Switching between "3 to go" and "4 to go" on the brightness scale turns the backlight on and off. Annoying, but I guess I can live with it and I do get some additional battery life.

Dec 31, 2010 4:58 PM

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Jan 5, 2011 4:44 AM in response to sammycw124 In response to sammycw124

I started having the same problem as well. I sent my MacBook back to AppleCare, but they said there was pressure damage and a fix would cost around $700. The IT guy at work is going to take my MacBook apart today, and try a screen replacement. I'll ask him for details on the problem, and repost here soon.

Jan 5, 2011 4:44 AM

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Jan 26, 2011 6:13 AM in response to fortyrod In response to fortyrod

My backlight goes off a few times a day. It is almost always while I am using the keypad, so it is not an issue of the computer falling asleep. I also tried switching the Power Saver settings, and that did not change anything. Luckily, when the screen goes black, I just have to click on the keypad to wake it back up. The situation is annoying but I'm concerned, more than anything, that someday the problem will become more serious (I only have a few more months left on Apple Care!) I parted with my MacBook for a week to have the Mac team fix this issue, and although they said it was fixed, it is not. Has anyone found a solution here? I am not sure whether it's worth taking it back to the MacStore again...

Jan 26, 2011 6:13 AM

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Feb 25, 2011 5:09 AM in response to Vannuch In response to Vannuch

Just thought I'd give everyone an update on the state of my Macbook...

I replaced the inverter board (third one...) but this time along with the cable as-well just in case that was the problem but alas no... Problem still there.

This leads me to think its either a problem with the cable on the other side of the inverter (the one going into the screen), the screen itself or the backlight.

I've started experiencing more and more lock-ups recently forcing me into hard resets and my bluetooth keeps becoming unavailable so I'm starting to think its a problem with the the logic board. 'll get a friends battery to see if its that causing the problem, but honestly I don't think it could be as some of you have said your batteries are perfect, mines been at the 'replace now' stage for ages but since doing a firmware update its now at normal with over 750 charge cycles. I've punished this thing.

I've run out of patience with it and not going to throw anymore money into it so I'll just have to put up with it for now. I constantly run in clamshell mode now so the only annoyance is the bluetooth failing for the mouse and keyboard.

I'll advise anyone with the problem to not give up hope that it could be something simple like the inverter but don't get your hopes up like I did.

Feb 25, 2011 5:09 AM

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Question: Backlight turns on and off randomly