IMac G5 Won't Start Up - Black Screen

[dodle]

I've got a 20" IMac G5 that was given to me. Some of its capacitors had gone bad so I replaced them and it was working fine. But, I hadn't used it for a couple of months and now when I power it up I can hear the startup chime and fans, but the screen never turns on.

Has anyone had this problem? Is there a fix for it?

[tiresia]

Are you running macosx or ubuntu?
Have you tried to reset pram (at bootup press cmd-opt-p-r)

[dodle]

I'm not running an OS as I am installing a new hard drive.

I've tried resetting the pram, same problem. Here is another symptom: After I shut it off, if I immediately try to turn it back on, absolutely nothing, no power or anything. If I wait a little bit longer, the power light turns on for a second then fades off. It seems like it has to be unplugged for a minute to turn it back on. I am double checking this right now.