RE084

Small Signal Triode — DHT — B4

Telefunken

Known Equivalents & Substitutes

A408A415L409KL70406LD410

Electrical Specifications

Absolute Maximum

Anode Voltage (max)Max Anode Voltage150V

Typical Operating

Anode Voltage (typical)Anode Voltage100V

Anode CurrentAnode Current4mA

Anode ResistanceAnode Resistance10,000Ω

TransconductanceTransconductance1.5mA/V

Amplification Factor (μ)Amplification Factor

Heater

Heater VoltageFilament Voltage4V

Heater CurrentFilament Current0.08A

Notes

Introduced by Telefunken circa 1927 for battery-powered receivers; filament designed for a 4 V battery supply.
Directly heated: the filament doubles as the cathode. Bias the negative filament end to set operating point.
Known equivalents: A408 (Valvo), A415 (Philips/RT), L409 (Zenith), KL70406 (Tungsram), LD410 (Tungsram) — all pin-for-pin compatible on the B4 base.
RE084k and RE084s are variants with slightly different filament or envelope construction but the same electrical characteristics and B4 base.

Pin Layout — B4

1Filament (+)

2Anode

3Control Grid

4Filament (−)

Socket-Compatible Tubes ⚠ Not electrically compatible

References