My son's 1.67GHz G4 15" Powerbook has all of a sudden refused to boot. No sign of life at all - with the exception of the ring around power adapter plug - which is illuminated when connected to the computer, as it should be. I've tried another power adapter just in case, but no change. Both of these power adapters are ok with another PB. I installed an SSD to this PB last year (which was a great improvement) and everything has worked fine until today. I've checked that the single 2 GB Ram module is securely installed, removed it, cleaned and refitted. No change. I know the battery is ok - 4 leds lit during self check. So in summary, it's refusing to boot from a known good battery, and also from a known serviceable power adapter. No chime or any sign of life from screen. Any advise please on troubleshooting this. Incidentally I have my own 1.67GHz G4 15" PB (a wonderfully 'clean' example purchased recently from fellow member Lastic), but at this early stage I don't plan any component transplanting from one to the other.