iMac G3 233 MHz (Bondi Blue) startup problem

[runbob]

Out of the blue startup failure. Push power button (keybaord or computer): chimes sound, power light goes amber then green, caps lock light flashes, computer shuts down. Unless the power cord is disconnected for about 30 seconds pushing the power button does nothing. If the power cord has been disconnected for 30 seconds the above scenario is repeated. Can not startup from CD or external HD. Cleaning and reseating memory chip and all connecting cables does no good. CD Rom drive and fan power up, but can't be certain about HD. Monitor always black. Where is the power supply for this computer located? Running OS 9.1 with 128MB memory. New 3.6v Lithium battery. Any diagnosis for startup failure, location of power supply or method for testing power supply without removal will be greatly appreciated.

Thanks