I let the charge run out of my G4 iBook the other day to recalibrate the battery but when I tried to turn it on again it wouldn't respond, with or without the charger plugged in. When I took the battery out it would turn on but just blasted the fans. I completely recharged the battery and it still gave me the blasting fans. I took it apart, made sure all the cables were tight and it still wouldn't boot. From time to time it would give me chimes, give me a grey apple and then a black screen (backlit). Then, after reading some google results I applied pressure on the case and tried it at various angles. Oddly, it came on when I tilted it, and thereafter would power up without tilting. However, it went into sleep mode earlier and wouldn't come out until I powered it off and on again. To add further mystery, when I manually put it into sleep it works fine, from Apple menu or lid closing. Google suggests a faulty logic board, but those posts all mentioned that the machines stopped working altogether. Mine is working but messing with my head. Is it a logic board on its way out or a connection I have missed when I took it apart? Cheers.