The R Type was from the beginning a hard vacuum valve. Hard pumping with the vacuum pumps of the day was a long process and to remove adsorbed gas from the metal parts heat was applied. This was successful but not complete. Over time, and when hot in use, gases would be released and bombard the electrodes. The use of gettering both shortened the pumping time and, after the valve was sealed, the getter would continue to take in gas molecules that evolved from other electrodes. Here we have a beautiful gold colour that is the result of using phosphorus as the getter. Only later bright emitters were gettered and this example is probably from 1923 or 1924.
The Marconi Osram Valve logo is etched into the envelope but is hard to see. The nickel plated brass base shell was used up to 1924 and then replaced with the cheaper Bakelite. SeeR Type for the later version.
The R etched into the glass. Below is the type one BBC stamp. This stamp was used from November 1922 until September 1924 and this fits with the phosphorus gettering dates.
The base shell has a paper label wrapped round it. The anode is horizontal - but not quite.
The grid helix is horizontal but as the anode is sloping the distance from grid to anode varies.
The operating conditions are on the label. Filament 4.0 V at 0.65 Amps with an anode voltage of 45 to 60 Volts.
The Base carries both G and A markings to give the user a guide to inserting the valve.
A closer view of the pinch and electrodes. The filament is open circuit.
The slightly distorted geometry and the remains of one end of the filament.
The plastic base has MOV Co. Ltd. in the centre. The pins are of the compound type with a brass split cover over the solid central core.
The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 97 mm tall.
References: Private communication, 1005 & 1003. Type R Type was first introduced in 1916.