The standard voltage converters are just transformers and do not change the frequency. Converters that include the frequency must be high quality (non triangular wave, trapezoid is better, sine is perfect).
However, using a simple transformer without changing the frequency is no problem, just change the tick jumper to vertical blanking (otherwise the clock will run slow). Usually switching PSUs have no problem with 60/50 Hz change.
Actually the best solution is to swap the PSU for a 240V one.
