The first prototype, registration E479.101 (Škoda factory number 4355), is completed by mid-1962 and in September it is displayed in an orange and white livery during the International Trade Fair in Brno
.
The second prototype, registration E479.102 (Škoda factory number 4356), also leaves the factory before the end of the year. Following the problems detected on previous
E 479.0 and E479.101 prototypes with the motors air cooling system allowing rain water to penetrate in the engine room, this unit is modified from the factory and fitted with open grills on the sides.
The
Czechoslovak State Railways (ČSD) refuse to take over these units (too complicated, faulty and heavy) and they remain the property of Škoda. In addition, the production of the S489.0 locomotive series was already planned.
These prototypes are not the only ignitron rectifiers locomotives built by Škoda at the time. Following the demand from
Bulgarian State Railways (BDZ) for electric locomotives with regenerative braking and in order to avoid imports from France and Germany, the Škoda factory is entrusted with the accelerated production of such machines in February 1961, originally with the delivery date of the first 10x units at the turn of 1961/2. These locomotives, registered as
E41, are built without a proper prototype development and long-term testing. Thus these units have very serious problems (including locomotive fires) and from 1965 are reconstructed by Škoda with silicon rectifiers and without regenerative braking.