The VR101 is a double-diode-triode that is directly equivalent to M-OV type MHLD6 and dates from 1940. This RAF receiving valve would have been used in superhet receivers as signal and AGC detector plus first audio stage.
The VR101 is pin-compatible with type DL63 but the heater current of the MHLD6 is 0.65 Amp as opposed to 0.3 Amp for the DL63.
The etched identification is within the standard M-OV lozenge but reads VR101 and thus shows that a large quantity were specially made to the RAF specification.
The VR101 and the stores code of 10E/280 are overprinted.
The top mica with control grid connected to the top cap. The cathode is rectangular.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 100 mm tall.
References: Data-sheet & 1043. Type VR101 was first introduced in 1939. See also1939 adverts.
