The Radio Micro Bi-Volt is a general purpose triode from 1926. The identification is so feint as to be almost non-existent. It reads Radio Micro Bi-Volt as the brand name changed to Dario in 1927 this exhibit must date to 1926/7.
The vacuum seal has failed and the gettering has turned to white powder. The electrodes have corroded.
The 1.8 Volt filament allows for a rheostat in series with the two Volt accumulator LT supply.
The black base cap with ribs for grip a long pinch stem and horizontal electrodes.
The grid wire is badly corroded. The tungsten filament is held in folds of the supports. The anode is a simple cylinder.
A closer view through the powder of the getter. The grid is welded along the length to the support rod.
The filament ha failed but the right hand end still has the wire present in the support fold.
The burned out end of the filament.
The wide glass tube envelope is 38 mm in diameter, and excluding the base pins is 80 mm tall.
Reference: 1043. Type Bi-Volt was first introduced in 1926. See also1926 adverts.
