Mauro:

Although the 75S-3 series receivers make no internal provision for 220 volt
AC operation, there is another option in addition to those already
mentioned.

It is possible to feed in the receiver's operating voltages from an external
supply that furnishes filament (6, 12 or 24 volts), +185 and -65 volts DC.
The 11 pin power plug used to feed in 110 volt AC also allows for external
supply voltages to be fed in, bypassing the power transformer. You could
build an external 220 VAC supply for a 75S-3.

A 2:1 step down transformer is clearly the simplest solution, and usually
simplest is best.

73,

Roger K6XQ