Military variant with 7V filament vs standard 2.5V — NOT a drop-in replacement
Electrical Specifications
Absolute Maximum
Anode Dissipation (max)Plate Dissipation (max)10W
Typical Operating
Anode Voltage (typical)Plate Voltage220V
Grid 1 Bias VoltageGrid Bias-40V
Anode CurrentPlate Current28mA
Anode ResistancePlate Resistance1,800Ω
TransconductanceTransconductance
Heater
Heater VoltageFilament Voltage7V
Heater CurrentFilament Current1.2A
Notes
The VT-52 is a military 'special 45' variant with a 7V three-section filament (vs 2.5V for the standard 45). It is NOT a drop-in replacement for the 45 due to the different filament voltage.
Filament specifications vary slightly between manufacturers: Raytheon rates 7V at 1.2A; Sylvania and Brimar rate 7V at 1.18A.
Originally designed for the BC-230 aircraft transmitter (SCR-183 radio set); the 7V filament was intended for 6.3V vehicle battery systems with voltage variation in flight.
Many VT-52s are tested and operated at 6.3V in audio applications, though the rated filament voltage is 7V.
Amplification factor varies significantly between manufacturers: Raytheon 3.6, Sylvania 3.8, Brimar 2.6. All agree on ra = 1800 ohms and Pa_max = 10W.
The EIA designation 2C45 was reportedly never formally registered. Complete manufacturer datasheets are considered largely lost; specifications sourced from partial datasheets reproduced in collector references.
DHT tube: the filament serves as the cathode; there is no heater-cathode isolation.
The British VT52 (without hyphen) on radiomuseum.org refers to the Philips EL32 pentode — a completely different tube. The American VT-52 is the 45 special.
Pin Layout — UX4
1Filament (f-)
2Plate (Anode)
3Grid
4Filament (f+)
Socket-Compatible Tubes ⚠ Not electrically compatible