KT63 — Beam Tetrode, Octal | Tubeofile

KT63

Beam Tetrode — Octal

Marconi-Osram

Known Equivalents & Substitutes

6F6GARP17CV1186CV1911NR85

Similar Tubes (Not Drop-In Compatible)

KT30

Electrically similar MO Valve pentode but B5 (5-pin) base vs Octal — not pin-compatible

Electrical Specifications

Section 1 — Beam Tetrode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)375V

Screen Voltage (max)Screen Voltage (max)285V

Anode Dissipation (max)Anode Dissipation (max)11W

Screen Dissipation (max)Screen Dissipation (max)3.75W

Cathode Current (max)Cathode Current (max)

Section 2 — Triode Strapped

Typical Operating

Anode Voltage (typical)Anode Voltage250V

Anode ResistanceAnode Resistance3,200Ω

TransconductanceTransconductance2.4mA/V

Amplification Factor (μ)Amplification Factor7.7—

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current0.7A

Notes

The KT63 is a beam tetrode while the 6F6 is a true pentode — they share the same pinout and similar characteristics but are not identical internally. The KT63 uses beam-forming plates instead of a suppressor grid.
Maximum ratings taken from RCA 6F6 datasheet as no GEC/Osram KT63 datasheet with explicit max ratings has been located. The Marconi datasheet specifies only 250V operating conditions and states 'Nominal Rating, see curve' for max dissipation.
Triode-strapped data from the Marconi KT63 datasheet: gm=2.4 mA/V, ra=3200 ohms. The 6F6 pentode gives slightly different triode figures (mu=6.8, gm=2.6 mA/V, ra=2600 ohms) due to structural differences.
TDSL lists Pout as 4.8W at Va=250V while the Marconi datasheet shows 3.0W — different datasheets report different output power figures depending on operating conditions and measurement criteria.

Pin Layout — Octal

1Shell (Metallisation)

2Heater

3Anode

Socket-Compatible Tubes ⚠ Not electrically compatible

References