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.
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""
If you are having problems and cannot see your screen put a light behind your screen and if you can see it now that means that you have backlight problems. This means that somehow you damaged probably some pins that give the light on the screen and I broke my MacBook pro today too randomly after getting Mac so it broke.
Albert Einstien 의
I have the same issue. Whenever I start-up and do a PRAM Reset, it starts of bright but dims just before it turns on. Tried every solution noted above except changing the LCD screen. I even changed the LCD inverter with no results.
I can move the brightness bar up and down with no change.
Of course, I have a 2009 IMac with High Sierra. I have a feeling it has to do with OS X version. It’s too much of a coincidence that all these older IMacs are suddenly having the same issue.
Alain Belanger 의
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