Why is my Screen Dim?

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MacBook Pro 15" Unibody Late 2008 & Early 2009

Released October 2008 / 2.4, 2.53, 2.66, 2.8 or 2.93 GHz Core 2 Duo Processor

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pbassey @basstech

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Postato: 28 apr 2016

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Why is my Screen Dim?

I realize this question has been asked and answered before and I apologize if this seems redundant, but my situation is a bit different. My MacBook Pro did have a normally functioning monitor when I first bought it off eBay. The hinge was damaged so the first thing I did was to replace the LCD with another one from a spare MacBook pro. The MacBook boots up fine every time, but the video is so dim that I can only see what on the screen by shining a flashlight onto the screen. Below are all of the steps I have taken:

I took the LCD panel off and put it on a different MacBook and that MacBook display looked fine so I know the LCD panel is fine.
I have connected the MacBook to an external display and everything looked fine
I have reset the SMC
I have reset PRAM
I tried the obvious - pressing F2 to increase the brightness
I checked the Energy Saver settings under System Preferences
I checked the connectors from the LCD to the Logic Board - all look tight and snug

At this point, I am at a loss. I do not know what else to check. Any advise would be greatly appreciated.

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Gautier @gautier11095

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Postato: 29 apr 2016

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Hello,

I suspect a damaged LVDS connector and/or LCD flex cable (a damaged LVDS connector may look just fine)

What happens if you put back the old display?

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When I swap in a lcd from a working MacBook Pro, the same result. Does not appear to be related to the lcd or the cables from the lcd.

29 apr 2016 da pbassey

then there are several possibilities (non exclusive):

- backlight pins of LVDS connector are damaged,

- backlight fuse is damaged (very likely),

- WLED chip (backlight driver) is damaged.

You can first try to measure the resistance of the fuse. If not 0, the fuse is blown.

If it's dead, measure resistance between each end of the fuse and the ground to see if there's a shortcut.

Please, do not try to bridge the fuse, it protected the rest of the motherboard!

Fuses don't die for no reason, you need to find the root cause before trying to replace it.

It blows for only 1 reason: a shortcut in the backlight circuitry (WLED chip, LVDS connector, LCD cable, LCD itself (very unlikely)).

If replacing the fuse can be done in any repair shop, replacing the WLED chip requires specific skills and should be done by a qualified professional.

Good luck :)

30 apr 2016 da Gautier

Thank you very much!

30 apr 2016 da pbassey

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When I swap in a lcd from a working MacBook Pro, the same result. Does not appear to be related to the lcd or the cables from the lcd. — pbassey
then there are several possibilities (non exclusive):

- backlight pins of LVDS connector are damaged,

- backlight fuse is damaged (very likely),

- WLED chip (backlight driver) is damaged.

You can first try to measure the resistance of the fuse. If not 0, the fuse is blown.

If it's dead, measure resistance between each end of the fuse and the ground to see if there's a shortcut.

Please, do not try to bridge the fuse, it protected the rest of the motherboard!

Fuses don't die for no reason, you need to find the root cause before trying to replace it.

It blows for only 1 reason: a shortcut in the backlight circuitry (WLED chip, LVDS connector, LCD cable, LCD itself (very unlikely)).

If replacing the fuse can be done in any repair shop, replacing the WLED chip requires specific skills and should be done by a qualified professional.

Good luck :) — Gautier