Powerbook g4 boots to blank screen

Just to make sure... You reset the PMU in accordance with these guidelines:

http://support.apple.com/kb/HT1431

To get the CD out try booting into Open Firmware:

Press the power button, when you hear the startup sound press and hold the Command-Option-O-F key combination, until you get the command line.

At the Open Firmware prompt, type: eject cd

While you are in Open Firmware try resetting NVRAM from here, with the following:

At the Open Firmware prompt, type: reset-nvram
Press Return.

At the Open Firmware prompt, type: reset-all
Press Return.

The computer should restart.

I believe that the powerbook came with 256Mb on the logic board so you could probably boot it with out the 512Mb stick in it.

It is possible that the logic board went bad... Was the Powerbook given you any problems before you stuck the memory in?

Well did you get the DVD out of the drive, cause you can run AHT (Apple Hardware Test) from the Tiger install DVD.

Have you tried to boot into safe mode.

You could make an appointment with at the Apple Genius bar, where they can look at it.

Hopefully someone else can shed some light on the subject. You may need to make an appointment to the genius bar or Authorized Repair Center.

Regarding your stuck CD: If you have the machine in pieces, it's child's play to remove the few screws that secure the top cover of the optical drive and retrieve your disc manually. You won't do it any harm this way as long as you're reasonably gentle with it (unless, of course, it has already failed mechanically and one of its control or disc transport arms is in your way). I'm not a technician, and I've done this several times.

If you've already reassembled the machine, power it on while holding down the trackpad button; continue to hold the button until the disc pops out. This is a hardware command, executed before the OS begins to load. If the optical drive works and is getting power, your disc should be ejected. (But the command has to be routed through the logic board, so it's possible that a specific failure on the LB could prevent it from being carried out.)

There is no RAM on your Powerbook's logic board other than the two removable modules in their slots, so it's no surprise that you couldn't boot with those removed.

Have you tested the known-good 512MB RAM module in each of the two RAM slots? Lower RAM slot failures have been common in that Powerbook model. Upper RAM slot failures, while they've been very rare, can also occur. I'm not sure whether or not the PB would give its three-beeps-at-startup indication of "no good RAM" or its one-beep-at-startup indication of "no RAM found" if both of the slots themselves were bad. I tend to think it would do one or the other, but I don't know that.

A brand-new RAM module, assuming it was a suitable one for the computer in question, really couldn't have "shorted out the logic board" unless there was visible deformation of the contact pins in the module or the slot it was seated in, or it was inserted incorrectly.