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

Mullard describe the UBC41 as a high gain triode for use as an AF voltage amplifier, combined with twin diodes, 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 moulded glass 'skirt' and locating pip.

The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 53 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.