Turns on to a sound, but No Display, No Picture

I have MacBook Pro 2009 A1278 that boots up and makes the booting sound, but screen stays black with no picture on it. Also, the laptop turns on only if the power cord is plugged in, if I unplug the cord and close the lid it stays on, but then if I open it to see the screen - it turns off.

I've checked the screen against the light from the back, and there is no picture on the display. (the screen was tested and is working with other laptops)

I have also cleaned all the connectors on the motherboard but it didn't help.

Please help.

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The first thing I would do is hook it up to an external monitor to see if it is generating a video signal.

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Agreed! Its the easiest test to isolate out whats happening.

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@oleidner - Any update here? Does the image show up on the external display?

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Measure pins 2, 3, and 4 on the LVDS connector for 3.3v, then measure pins 21 and 22 for 27-35v. If this is not present, you have no backlight, no image, or no recognition of the LCD. Which is missing?

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oleidner will be eternally grateful.
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