I have an old Imac G5 which is hanging randomly and have some time to fix, so going to give it a try. I have tried to repair the caps before because the video went wonky. I subsequently replaced the motherboard. When it hangs now, the fans go on high setting. The only way to shut it down is to press and hold the power button. I checked the board, caps are fine and did the various memory resets holding down the ctrl keys etc. But this has not helped. Another thing I did was I tried to install the OS on a new hard drive, but it got hung up in the install process also, so thinking its some hardware that is the issue. Any suggestions would be helpful.