The type UY-227 triode is also known as the 27. It is an early indirectly heated audio valve with a good reputation for performance.
Westinghouse announced a double ended indirectly heated cathode in an article in 1922. The valve became the UY-227 and the UY base was adopted in 1927. The UY-224 screened grid valve was a development of the UY-227.
With 90 Volts on the anode the grid bias should be -4.5 Volts. At 135 Volts on the anode the bias should be -9 Volts. At the absolute maximum anode voltage of 180 Volts the bias should be set to -13.5 volts. The heater cathode voltage should not exceed 9 Volts.
The vertical mesh anode with helical grid within.
The five pin UY base. The details pressed into the base are RCA Radiotron and UY-227.
The base wording.
The RCA logo etched into the dome. The heater wire is encased in a ceramic tube and filled with insulating material.
The mesh anode with helical control grid within. At the centre is the oxide coated cathode tube with the ceramic heater tube within.
The data sheet placed in the box with the valve.
The license conditions.
The balloon envelope is 44 mm in diameter, and excluding the UY base pins is 98 mm tall.
References: Datasheet, 3002, 1043, 1047 & 1040. Type UY-227 was first introduced in 1927.