845

Power Triode — DHT — UX4

RCA

Known Equivalents & Substitutes

UV845VT-43CV735545C84538145845WR845T845

Similar Tubes (Not Drop-In Compatible)

284A

WE transmitting triode listed as similar to 845 in RCA interchange guide; different filament and operating conditions

384D

WE transmitting triode listed as similar to 845 in RCA interchange guide; not pin-compatible

945

Transmitting triode listed as similar to 845 in RCA interchange guide

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Plate Voltage (max)1,250V

Anode Dissipation (max)Plate Dissipation (max, ICAS)100W

Cathode Current (max)Plate Current (max)150mA

Typical Operating

Anode Voltage (typical)Plate Voltage (typical, Class A1)1,000V

Notes

DHT tube: the thoriated tungsten filament serves as the cathode; there is no heater-cathode isolation.
Graphite anode permits 100W plate dissipation (ICAS). CCS rating is 75W.
Class A1 amplifier at Va=1000V: Vg=-98V, Ia=65mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=5600 Ohm, Po=15W.
Class A1 amplifier at Va=1250V: Vg=-123V, Ia=80mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=6600 Ohm, Po=23W.
Class B audio push-pull (2 tubes): Va=1000V, max-signal Ia per tube=120mA, Po=50W; Va=1250V, max-signal Ia=150mA, Po=78W.
The 845W is the ruggedised variant with identical electrical characteristics.

Pin Layout — UX4

1Filament (f-)

2Plate (Anode)

3Grid

4Filament (f+)

Socket-Compatible Tubes ⚠ Not electrically compatible

References

Grid 1 Bias VoltageGrid Voltage (Class A1, Va=1000V)-98V

Anode CurrentPlate Current (Class A1, Va=1000V)65mA

Anode ResistancePlate Resistance1,700Ω

TransconductanceTransconductance3.1mA/V

Amplification Factor (μ)Amplification Factor5.3—

Output

Output PowerOutput Power (Class A1, Va=1000V)15W

Load ImpedanceLoad Resistance (Class A1, Va=1000V)5,600Ω

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance6.5pF

Input CapacitanceInput Capacitance7.5pF

Output CapacitanceOutput Capacitance3.3pF

Heater

Heater VoltageFilament Voltage10V

Heater CurrentFilament Current3.25A