After my friends Powerbook G4 was yanked off a table by the power cord it wouldn't start up at all and the light did not come on when the AC adapter was plugged into it. I ordered the DC-In board and replaced it.

Now it starts up fine, and charges the battery fine, but, no video on the LCD, not at boot, not when booting from CD, BUT, when I attach an external display, everything seems to work fine, and, if I go to System Profiler, it shows the video card but no attached video device besides the external monitor.

I've reset the PMU and zapped PRAM.

What are my next steps for troubleshooting?
Video Display cable? Display?

Any suggestions greatly appreciated.
Thanks,
Bill

If there is no backlight and no picture, that is generally a logic board problem unless you forgot to plug in both cables.

If you can make out a faint image but the backlight doesn't come on, that is going to be something wrong with the inverter board or cable.

I have a similar problem. I am working off of an external monitor.

My LCD looks like it has a backlight but no image. It changes from black to very dark grey on boot up, but i cannot make out any image.

I would like to try to fix it myself, what would you try first?

a good trick to seeing if it is a backlight problem is getting a flashlight and shining it right into the Apple logo on the back of the display. If you can then see a picture, you have an inverter board/cable problem.