Converting Pass Labs XA60.5 from 120V to 220V

Hi,
My friend bought Pass Labs XA60.5 when he had been in USA. So it's voltage setting is 120V.
Now he is in Korea and using it with voltage converter.
But he hopes to use it without voltage converter.
Is it possible to convert PL XA60.5 from 120V to 220V?
Any advice or document such as service manual would be helpful.
Thanks