Apple Power Supplies: Changing voltage settings
iMac
iMac (Early 2006) Auto-Switching
iMac G5 (iSight) Auto-Switching
iMac G5 (Ambient Light Sensor) Auto-Switching
iMac G5 - all models Auto-Switching EXCEPT models sold in the US, Canada, and Japan (these models support 100-127 V AC)
iMac G3 and G4 - all models Auto-Switching
iMac (Mid 2006) Auto-Switching
iMac (Late 2006) Auto-Switching
iMac (Mid 2007) Auto-Switching
iMac (Early 2008) Auto-Switching