I gave a dual processor G5 Mac Pro that wont start. This happened after it had sat unplugged fro a prolonged time. Now when I push the startup button, the power light goes on momentarily, there is a click, and then the power light goes off. I have replaced the 3.6V battery and pressed the small setet button on the logic board. Still same problem.
Thanks very much for the responses.
There is a red LED near the power button that flashes momentarily before the power shuts off.
Resets involving key combinations are not a posibility because the machine will not power on.
You can try resetting the NVRAM. When you press the power button, hold down cmd-option-O-F
When you get to a promt, type reset-nvram and press return.
Then type reset-all and press return.
If this doesn't work, you may want to consider looking on ebay for a replacement power supply, although it's also possible the you have a bad logicboard/motherboard.
Unplug all peripherals, Monitor & power, pull PRAM Battery, let sit 30 minutes, hook power back up, put PRAM Battery back & see if it starts.
Also check if there's a red led lit on the logic board & that the plastic sheilds swith/sensor hasn't come loose.