If you have to ask, then maybe its not such a good idea to try
Having said that, many times a manufacturer will have both 220 and 120 taps on the primary transformer in the power supply if it is an 'export' model. So, it would be a matter of switching the wire over to the correct terminal on the transformer and changing the plug if needed. Though, I know in the D5500 Omegas, the 'switching' power supply is not amenable to easy voltage conversion.
If it is a condenser head, and the bulb runs right off the mains, it could be as simple as just replacing the bulb.
The other way would be to get an external step-down transformer of the appropriate wattage and not alter your power supply.