Mac G5 spontaneously shuts down
I have an older single processor Power Mac G5 (1.6 G I believe) that began shutting down for no reason. It now will not boot - but starts the process normally - with the chime and the fans - but then shuts down after about 15 seconds. I have checked the power supply and am getting 5 volts - I checked the pram battery - and am getting 3.5 volts. I do not see any physical signs of capacitor problems. What am I missing here??