During 1974 two locomotives (units 056 and 057) were provided with a "shunt chopper" system (later the modifications applied were rolled back, making the two units identical to standard once again), while in 1975 the E.444.005 adopted a "full chopper" electronic system, which was later also adopted on the E.632/633 classes, and which granted a 5000 kilowatts peak power.