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Screen *extremely dim* on boot, external display works great

I've got an issue with a MBP 15, with a screen that is dim though connecting it to an external display with the screen disconnected works like a champ (POSTs/Chimes and boots right on up).

Here's what I've done (swapped out/replaced):

4 different inverters with no change

2 different I/O boards with no change

1 cable change (one that connects to IO and logic/motherboard)

3 different LCDs (one of which I'm using as I type this)

As I've stated before, if I disconnect the LCD/chassis and boot up with an external display connected it works fine. Connected, it's D I M , but you can still see it boot in the right angle/lighting.

Forgot to mention, also tried resetting PRAM and SMC as well.

Model number is A1260, last three of serial are "1XR".

I've also ran the Apple Hardware Diagnostics from the factory disc, which doesn't report any errors when hooked up to an external display with the display disconnected

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Need to know your EXACT model to get you to the correct part. Please give the last three letters of your serial number.

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Apple MacBook Pro "Core 2 Duo" 2.4 15" (08) Specs

Identifiers: Early 2008 - MB133LL/A - MacBookPro4,1 - A1260 - 2198

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Sorry for the delay, work has been keeping me busy. I've attached a pic. I read through ABCellar's post which has disappeared since then. I have a buddy who has steadier hands and is better at soldering help determine the voltages for the power that the screen was getting on my working MacBook Pro. For what ever reason, the inverter on the one I've been having problems with was not getting any power, the I/O-Soundboard's inverter connector was essentially dead power wise. He wired a wire from the motherboard connector to the power pin on the LED power connector on the I/O board. not sure if this would be the absolute correct way to fix this, but it's going to work for my purposes. Now that there is power to the screen I can see the camera doesn't appear to be detected, so I'm not sure if the fix has affected it, or if the camera was out to begin with, not a big deal though. If you have any other ideas or comments about this fix, please let me know. Thanks for all y'alls help!

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Sorry for the length of silence, but work has been keeping me busy. I appreciate all the suggestions, and luckily I found a "rigged" fix. I've attached a picture. I read through ABCellar's post which seems to have disappeared since then. I have a buddy who has steadier hands than I do and is better at soldering help determine the voltages and figure what the correct numbers were for the power that the screen was getting on my working MacBook Pro. For what ever reason, the inverter on the one I've been having problems with was not getting any power, the I/O-Soundboard's inverter connector was essentially dead power wise. He wired a wire from the motherboard connector on the I/O-Soundboard to the power pin on the LED power connector on the I/O-Soundboard. It's not exactly pretty, not sure if this would be the absolute correct way to fix this, but it's going to work for my purposes. I do know at this time now that there is power to the screen that the camera doesn't appear to be detected, so I'm not sure if this fix has affected it in some way, or if the camera was out on this unit anyway (not a big deal since I don't use it). If you have any other ideas or comments about this fix, please let me know. Thanks for all y'alls help!

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Sounds like you have tried everything there is to try. When you say that you have changed the cable that connects I/O to logic board, are you referring to the LVDS cable that goes from the inverterboard to Logicboard? If you havent changed that Data cable, I would try that. If that doesn't succeed, then you might be looking at a bad connector on the LogicBoard itself.

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Double check your connections in step 27. MacBook Pro 15" Core 2 Duo Models A1226 and A1260 LED Driver Board Replacement If you feel confident about that connection replace the cable/wires that goes from the logic board to the LED Driver Board/Inverter. The LED Driver Board/Inverter cable is "married" to the iSight cable. That part is here: MacBook Pro 15" (Models A1226/A1260) Inverter/iSight Cable The procedure for changing the cable is here: MacBook Pro 15" Core 2 Duo Models A1226 and A1260 iSight Cable Replacement

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Quadruple checked the connections :-) . I actually took the display assembly and tested on a known good Macbook Pro, screen light right up, so that says the cables and connections are good. I went ahead and took out the logic board and inspected for any issues. Since I've had this particular MBP a while before really getting into fixing it, I can't remember if I've brushed it down with denatured alcohol or not, so I've swabbed it down a little and I'm currently waiting for it to dry.

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Ok Josh....Any new findings?

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Josh Douglas will be eternally grateful.
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