Loewe produced the 3NF multi valve to avoid excessive taxes levied on the number of valves in a set. The three triodes and associated passive components sealed into the envelope are used to make a complete radio with a minimum of external components. The 3NF was the first integrated circuit. The passive components (resistors and capacitors) were sealed in glass tubes prior to final assembly.
This exhibit has lost the identification markings. This lettering is present on our other 3NF exhibit.
The side triodes are assembled on a glass rod support before the final assembly. The central triode is larger and mounted vertically. One end of the filament of both side triodes is supported by a copper rod. This may be a copper plated spring to tension the filament. The thoriated tungsten filaments are retained by folds in the supports.
The right side of the filament in the side triode can be seen to be held in a fold of the support. on the extreme left is a small copper coil.
The control grid pitch is identical in both side triodes.
The central triode is enclosed by a mica box.
Internal supports are glass rods that support wires wrap round.
The base has three support pins. Their spacing is such as to prevent incorrect insertion into the special bayonet base.
The open base. The lead-out wires are soldered into the pointed brass pins. There is an insulated wire in the centre that is not connected to any pin. This is also present on our other 3NF.
Close-up detail of the side triodes.
The details of the central triode are masked by the mica box. A single filament strand is present together with a helical grid. The copper coil is clearer in this image.
The wide glass tube envelope is 46 mm in diameter, and excluding the base pins is 160 mm tall.
Reference: Data-sheet. Type 3NF was first introduced in 1926.