My G5 Mac pro can't boot up properly, when i press the power button, can see the light, also can hear something startup and can even see the apple grey color on screen, but this doesn't last long, may be only 3 seconds, sometimes only last 1 second, then it powers off by itself and fails to boot. I tried so many times, got the same result.
I have took out the battery, and replace a new one , the result. please help. thanks