Recently my PowerBook G4 12" is having problems booting. When I go to power up I head the Apple Chime and the screen remain black. This problem is not always present, sometimes it will function normally. I reset the PRAM and the PMU, but this doesn't seem to have done anything. I have also noticed that when the machine fails to start that the sound of the CPU powering up is not present. I can tell just by listening to the machine if it is going to boot. If it doesn't boot there is no sound, however, the caps lock and number lock lights are present. Can any of you guys give me some advice? I am suspect to the logic board slowly failing. Are these some of the symptoms associated with a failed logic board? Pleas help!