Imac will not power an external monitor

My Imac G4 has a black screen on which I can see the apple desktop with a flashlight. I hooked up an external monitor to see if I could salvage the computer abut the new monitor says "no signal." Based on other posts I thought it might be the inverter, but any advice would be appreciated?
Thanks

Sorry about my lack of details, I am using the Apple brand of display port to DVI adapter, a DVI cable that is plugged into an ACER 26" monitor (not sure of the model nuimber right now as I am at work).  This monitor and DVI cable worked fine during reboots/shutdowns, etc while connect to 2 different Intel based PC's that I have that also run dual monitors.  As I mentioned I've done PC work for many moons and would know how to check for drivers, etc, but now in the Apple environment I am lacking these same skills. So I've done all the standard stuff, switching known good cables etc, but I am unsure of how to uninstall drivers and those type of tasks if need be.  I know it could be a monitor problem, but that same monitor works fine while connected to the PC's that I have.

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