This exhibit is a Cunningham double filament tubular Audiotron number 110 (#110). The advert above shows the valve as wire ended. In 110# and 110# the valve has been fitted with a separate UV base and in 110# an ebonite base has been made. Here the valve has been joined to a B4 base from an R Type valve.
The paper identification label is marked 'Audiotron' and is of the earliest type used by Cunningham. The man himself later became a significant figure within RCA.
The double ended envelop has the filament and grid connections at the top with the anode at the bottom together with the filament centre support and contact. The anode is a plain cylinder that looks to fill the width of the glass.
The leads from the top connects are twisted and soldered to extension wires that are then soldered to wires in the donor base. The green braided wire is the grid and connects to the grid pin of the base. The two filament wires are connected together and pass to just one of the filament pins. The centre support, and thus centre tap, connects to the other filament pin. Sadly the filament is open circuit.
The copper base cap with the valve logo with the letter R at the centre. As yet we do not have an identification of the company who used this logo.
The base insulator and pins match those used by Metal for the TM.
The copper helical grid is supported only at the other end and vibrates when the valve is moved.
The cement holding the valve to the B4 base cap.
Here the two filament wires can be seen to be twisted together and joined to the wire passing down to the base.
The microscope reveals the centre filament connection and the unsupported end of the copper grid.
One of the filament end connections.
The thin glass tube envelope is 21 mm in diameter and, including the UV base pins, is 106 mm tall.
Reference: Joe Gruber and advert. Type 110# was first introduced in 1916. See also1916 adverts.
