6CB5A — Beam Tetrode, Octal | Tubeofile

6CB5A

Beam Tetrode — Octal

RCA

Known Equivalents & Substitutes

6CB56CL56P20S

Electrical Specifications

Section 1 — Beam Tetrode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)880V

Screen Voltage (max)Screen Voltage (max)220V

Anode Dissipation (max)Anode Dissipation (max)26W

Screen Dissipation (max)Screen Dissipation (max)4W

Cathode Current (max)Cathode Current (max DC)240mA

Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)200V

Max Grid ResistorMax Grid Resistor0.47MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage175V

Screen Voltage (typical)Screen Voltage175V

Grid 1 Bias VoltageGrid 1 Bias Voltage-30V

Anode CurrentAnode Current90mA

Screen CurrentScreen Current

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance0.4pF

Input CapacitanceInput Capacitance22pF

Output CapacitanceOutput Capacitance10pF

other

Mu-Factor (Grid No.2 to Grid No.1)Mu-Factor (Grid No.2 to Grid No.1)3.8—

Section 2 — Triode Strapped

Typical Operating

Anode Voltage (typical)Anode Voltage253V

Grid 1 Bias VoltageGrid Bias Voltage-50V

Anode CurrentAnode Current40mA

Anode ResistanceAnode Resistance700Ω

TransconductanceTransconductance

Heater

Heater VoltageHeater Voltage6.3V

Heater CurrentHeater Current2.5A

Notes

Plate connection is via a top cap (JEDEC No. C1-1), not through the octal base pins.
Pins 4 and 5 are both connected to Grid No.1 (control grid).
Pins 3 and 6 are both connected to Cathode/Grid No.3 (suppressor internally tied to cathode).
Pin 1 and Pin 8 are both connected to Grid No.2 (screen grid).
Originally designed for TV horizontal deflection, not audio. No manufacturer audio operating point or output power data exists.
An adequate bias resistor or other means is required to protect the tube in the absence of excitation.
The 6CB5A is unilaterally interchangeable with the 6CB5 (improved version).
Triode-strapped data sourced from Bartola Valves (https://www.bartola.co.uk/valves/tag/6cb5a-triode-mode-curves/), not from the manufacturer datasheet.

Pin Layout — Octal

1Screen Grid (G2)

2Heater

3Cathode

References