Around 1965 Lenco improved the VV6 using now silicon transistors and re-named it to VV6 S. During the production Lenco changed also the transformer again and a fuse was added. In the official drawing of this Mk IV version this fuse is on the primary side of the transformer but in practice it was inserted on the secondary side! An additional sheet improved the shielding from the line transformer.

It was replaced in 1967 with the VV 7.

During my research I discovered the Mk III, using still the same PCB but now with Silicon transistors. It has still a NTC in the emitter path and the rectifier diode is still an OA 81

VV6 S Mk IV with an additional sheet between the transformer and the second channel.

Under the aluminum shielding cover was a single silicon transistor and all the elements for a RIAA equalisation.

VV6 S (Mk III) schematic.

VV6 S (Mk IV) schematic.