If the power button's light goes amber or bright without any response, that may indicate a bad P.A.V. board (Power Analog Video); that's the huge circuit board that sits underneath the CRT picture tube. It also has the flyback transformer, high voltage (10,000 volts or greater), etc., on it. That may need replacing. Not uncommon for that to happen on the iMac G3s or eMacs for that matter.

73s de Phreakout. :rambo: