On Power Macintosh G3 (Blue and White) and Power Mac G4 computers, it is important to make sure that the power cable is connected to the internal Zip drive before powering up the computer. If only the data cable is connected, the computer will start up to a black screen.
If this should occur, power down the computer and make sure both the data and power cables are properly connected to the internal Zip drive then restart the computer. If the situation persists, consult your Apple Authorized Service Provider for further troubleshooting.