If the appliance is "slash marked" to work on 50-60Hz and voltage convertable-no problem-I am referring to appliances designed to run from 120V 60hz only.For the voltage-if the device can be used you will need a transformer to step 220V to 120V.If the appliance can be converted to run on 220v fine.some motors and appliance transformers are like this.they can be configured to run on either voltage or frequency.If the device is all electronic-generally no problem.The incoming AC is rectified and goes from there.I used to deal with tape machines and turntables that had motors slash marked for 50-60Hz power.The machine had two pulleys for the motor-one for 60Hz,other for 50Hz-and the motor windings could be configured for 120V-220V.Otari tape machines had transformers in them-the machine could be used on 120V or 220V 50-60 hz.You only needed to configure the machines transformer primary for the voltage required.the motors were electronically speed regulated.