I do not know the exact pinout, but the pinout for the 17" will not work. The backlights on the 20" LCD need 24V. I would guess that there are 2 - 24V lines, 2 - grounds, 1 on/off - which I would recommend hooking up to low voltage such as putting a 1 Kohm resistor between the line and 3.3v. 1 - dimmer, which you could probably leave floating. Again this is a guess, but I am certain that a 24V line is needed. Hope thus helps.
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The iMac G4 forever changed the way I viewed computers. With some modification it can be used as an external monitor or updated all-in-one computer.