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Display is dim and will not brighten

The image on the display of my MacBook Pro A1278 is very dim. I'm not sure but I don't think that it's the backlight since the image is visible enough that the laptop can still be used but the screen lighting is very dim. The brightness adjustment on the F1 and F2 keys do nothing when either one of them is held down. The brightness adjustment in the System Preferences doesn't do a thing to dim or brighten the screen image. Is this a common problem and is there a fix for this problem.

Отвечено! View the answer У меня та же проблема

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Don, sounds like either a bad inverter or a bad backlight. What are the last three of your serial number? This will identify your computer a bit better and might help to further trouble shoot.


The complete serial number is W89024X31AQ. In an effort to try to diagnose the problem myself I took the display off my daughter's old A1278 that had died some time ago and put it on this one and the problem is still there. My daughter's laptop was working perfect until it stopped turning on so if the problem I'm experiencing is in the display I think that it should have fixed the problem, but it didn't. Nothing that I have done seems to make the light adjustment better or worse. When I hold F2 down the light image is displayed on the screen and the bar below it indicates that the light is being increased but the display light doesn't change at all. When I hold down F1 the bar indicates that the light is being decreased but it doesn't change a thing on the display screen (either of the screens that I have tried out).


Does this look about right :"Intro Date: October 14, 2008 Disc Date: June 8, 2009

Order No: MB466LL/A Model No: A1278 (EMC 2254)

Subfamily: Late 2008 Aluminum Model ID: MacBook5,1

Std RAM: 2 GB Std VRAM: 256 MB

Std Storage: 160 GB (5400 RPM) Std Optical: 8X DL "SuperDrive""


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Don, first I must admit that I am not a Mac person. So this answer is a general answer and hopefully the Mac Guru's can help you out further. Since you already replaced the LCD with a working one, it is possible that this is caused by a bad inverter. Try to connect an external display and see if that works. If so, then it is the inverter/backlight circuit of your computer. If it does not, then you are having GPU trouble on your computer. Apple suggest:" No display or dim display, but computer appears to operate correctly and has video operating on external display (display is fine after startup, but after a few seconds no display or dim display)

1. Remove any connected peripherals.

2. Try known-good power outlet, power adapter, and power cord.

3. Press F2 (with the fn key pressed and not pressed) to increase the screen brightness setting.

4. Reboot the computer—hold down the Control and Command keys and press the Power button, or press and hold the Power button for 5 to 10 seconds to shut down the computer, then press the Power button to restart.

5. Reset the SMC. See Knowledge Base article 303319, “Resetting MacBook and MacBook Pro System Management Controller (SMC)”. Resetting the SMC means you will also need to reset the date and time (using the Date & Time pane of System Preferences).

Warning: Make sure you do not hold down the “fn” key when resetting the SMC.

6. Reset PRAM. Restart the computer, then hold down the Option-Command-P-R keys until you hear the startup sound at least one additional time after the initial startup sound.

7. Connect an external display, and check for video on external display.

• If video is fine on external display, troubleshoot LCD panel and verify cable connections to inverter and LCD. Verify battery connector with sleep switch connection.

• If video symptom is same on external display, replace logic board.

8. Verify that LCD panel cable and LVDS cable connections are seated properly and that the cables are not damaged. Check cables around the hinges for damage.

9. Replace Inverter board.

10. Replace battery connector with sleep switch.

11. Replace LCD panel.

12. Replace logic board.

If the numbers are right, then you have a fuse for your backlight on your logic board. It is a 2AMP-32V SMD fuse. Test it with a multimeter and see if you have continuity. If not then you need to replace that. Hope this helps, good luck.

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Well, I guess that it really doesn't matter at this point since my computer finally quit all together. I now assume that the problem all along has been a weak logic board that finally just decided that it had, had enough and gave up and quit.


Almost forgot, I want to thank oldturkey03 for at least trying to help me out. THANKS


F2! It worked, thank you so much


#4 worked!! Well, for the dimmed part anyway. Thanks!!


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Yesterday my Mac was also doing that I have tried everything like pram vram smc and then with frustration removed battery and opened its back cover with screw driver. Unplugged all tiny mini cables n given some heat with heat gun replugged all cables fixed its back cover and now my MacBook is running perfectly. Remember guys i suggest u to do all these things very carefully. u don't need to pay for repair because we can solve these tiny mini problems

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Dear Mr. Ansari

This problem after update os, why i need open laptop and change any hardware issue.




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Hi Team,

I having the same issues tried everything that is been mentioned here.

1. Reset SMC

2. Showed to a local Shop he says connector are ok seems to be a issues with Screen ..

3. When i connect to my TV it works like a charm.

4. Apple is asking 90% cost of the machine for the New Screen which i dont wanna spend

Any suggestion if you guys can give .. really need my Mac back can't use it as a Desktop .



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Don будет вечно благодарен.
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