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The UBC41 is a double diode triode valve on a B8B base. Early B8B valves like this exhibit had a metal skirt and/or locating spigot. On later production the skirt gave way to a wholly glass construction with a moulded locating pip to fit into the key slot on the holder.

The UBC41 is a high gain triode for use as an AF voltage amplifier, combined with twin diodes. Application is for for DC/AC mains operation.

In general, TV sets using a series heater chain had to use 0.3 Amp 'P' series valves so that the total voltage of the heater chain (17 valves, say, plus tube) was less than around 170 V. This was to allow operation from 200/210 V mains after making an allowance for voltage drop in a series surge limiting resistor. The 100 mA 'U' series were mainly used for radio receivers where fewer valves were used.

The outer perforated screen is in two parts with a central mica sheet. The triode is in the lower part. In the top section the cathode tube has a small patch of oxide near the top and either side of this are placed the small diode anodes.

The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 51 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type UBC41 was first introduced in 1949. See also 1949 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.