Currently Being ModeratedFeb 19, 2013 9:18 PM (in response to JKLI)
CD-RW/DVD-ROM combo drives have an optical pickup unit having (2) laser diodes, which control recognition of the type of media inserted (CD/CD-R/CR-RW or DVD-ROM) and appropriately adjusting the frequency of the laser beam. Failure of either can render the drive incapable of recognizing/reading one type of media. Replacement of the optical drive in a G4 iMac is a bit involved, as it requires removal of the bottom housing to access and remove the drive carrier containing the hard drive and optical drive. If you've taken it apart before, you know what I'm referring to. The easiest solution would be to use a FireWire-connected DVD±RW drive, which would give you the additional capability of burning data DVDs.
Currently Being ModeratedFeb 20, 2013 6:16 AM (in response to Jeff)
Thanks Jeff. I have succeeded in connecting an external unit that works fine. I wasn't aware of the distinction in laser diodes, so you saved me from wasting more time on this. Appreciate the good info.