Sensibly equivalent¶ to:
The RG3-250A is a half wave mercury vapour rectifier. The A variant has a top hat top cap whereas the RG3-250 has a screw connection. Mercury vapour rectifiers need carefully-profiled anodes no larger than the cathode shield area. Keeping such a small anode cool when the valve is handling high current was one of many problems which had to be solved by the designers of vapour rectifiers. The heavy-duty top cap is an anode heat-sink on to which would be clamped a heavy-duty finned connector, probably cooled by a fan.
This half wave mercury vapour rectifier was still listed by Mullard as current production in the mid 1960s.
Spots of mercury can be seen on the inside of the envelope. Construction is heavy duty as befits a valve working at a quarter of an Amp at 3500 Volts. The maximum reservoir capacitor for this rectifier is 2 µF.
The classic envelope is 44 mm in diameter and, excluding the UX4 base pins, is 117 mm tall.
References: Data-sheet & 1040. Type RG3-250A was first introduced in 1938. See also 1938 adverts.
Absolute Maximum Operating Conditions¶
PDF scanned from an original document held by the museum
Updated January 03, 2022.