I have the exact same problem with a 7200. I got it from a friend who had had problems with it. I get the chime, but thats it, no video, no hard drive activity, nothing. It won't boot from a floppy either.
I searched through Apple's TIL, but nothing worked. I replaced the battery. Left the battery out for 30 minutes, tried the CUDA button, zapped the PRAM. Nothing works...
Sorry I don't have any helpful suggestions.