Cheers gang.
I recently acquired a G4 Mac Mini but trying to get it to cooperate is proving a headache.

When I got the system, it was able to boot into OS X just fine and I could get the open firmware boot menu by holding down keys on the keyboard.

However, when I shut the system down and went to prepare a USB stick with the MorphOS installer on it, it seems something happened.

Now the system will not boot to OS X or to the open firmware screen.
I hear the "chime" when I turn it on, but regardless of whether I just let it sit or try to hold down the keys for open firmware, the screen just goes black, as if nothing was plugged in.

Any suggestions for things to try?