Odd problem with MBP backlight

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Qtip42

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Mar 16, 2000
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Go figure something completely random would mess with me this week.

One of our MBP's was working perfect and randomly the screen went dark (2% backlight?) after rebooting. At first I had thought one of our diamond inlays was pressing too hard against the screen or had damaged it. Tried and SMC reset, nothing. So I got a new screen, same problem with that as well (though I tested it without the display housing on back). I tested the new screen on another MBP to verify it was indeed working. Next I tried swapping all parts one by one including the ambient light sensor on the left side. Still no fix. I've tried the keyboard brightness settings, nothing...nothing..nothing. Tried a few random google searches and haven't found any good ideas so ...

So I'm left with this oddly dark screen and I can't help but think something is off with the logic board. Anyone have an idea what could be going on?
 
my guess is that it is the LCD's backlight inverter needs to be replaced.
 
is this on one of the LED back-lit displays? When the back light goes off, there's still dim video shown on the display?
 
Ya it's led....Everything runs fine I just can't hardly see the cursor or any of the windows it's so dark.

On the other hand, I tried swapping to a different screen (again) and I can't see anything on that one (one screen is a Samsung the other is LG Phillips)
 
Hmm strange, I'm stumped... is the back light inverter housed in the lid or somewhere under the keyboard. I thought it was always in the lid, because they make those things so small nowadays... but maybe its changed with the led backlit ones... if the bum inverter is separate from the screen in the notebook's housing, maybe that's why swapping just the screen didn't work?
 
It's under the the plastic at the bottom of the screen.

I have 3 screens (all fully constructed except I leave the display housing off). I've swapped wiring (including inverter) among other things. Did it a second time just to make sure after you said it yesterday. Usually the only issues I run into when building these things is a screw that breaks or something simple but this has me scratching my head. I've got an extra logic board I haven't tried yet so that's my next step. I still need to figure out what's going on with this one though.
 
Possibly a software issue? Have you tried booting from the restore DVD to see if the problem persists?
 
felix88 said:
Possibly a software issue? Have you tried booting from the restore DVD to see if the problem persists?
Click to expand...

Swapped drives. That should have fixed it. I guess I could try the dvd.

Yours is hopefully delivered tomorrow (finally!). I was told the battery cover it's waiting on is being delivered in the AM. Looks really good though. Probably the best one so far of all I've done.

I still have to figure this other one out though since the rest of the MBPs I have already have deposits down on them :\ Hate to have to buy a new logic board.
 
Upgraded to Leopard.........no change. Tried a new logic board.......strangely no change either.

It had worked once before with this logic board so now I'm officially baffled. I tried a firmware update only to be told it did not need it. I'm starting to wonder if for some reason it would rather have a different branded screen. I have an LG and Samsung, both are dark. Also the brightness controls do not work at all. Doesn't change anything whether they're on full or zero.

Anyone got anymore ideas?
 
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