HCH81

Triode-Hexode — Noval

Philips

Known Equivalents & Substitutes

12AJ8

Similar Tubes (Not Drop-In Compatible)

ECH81

6.3 V heater version — same Noval base and pinout but different heater voltage

Reportedly identical internally to ECH81 — same base and pinout

19 V / 100 mA series-heater version — same pinout but different heater voltage

Electrical Specifications

Section 1 — Triode (Oscillator)

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)100V

Anode CurrentAnode Current3.2mA

Section 2 — Heptode (Mixer)

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)200V

Screen Voltage (typical)Screen Voltage (g2+g4, via 10 kohm resistor)119V

Grid 1 Bias VoltageGrid 1 Bias Voltage-2.3V

Anode CurrentAnode Current3.7mA

Screen CurrentScreen Current (g2+g4)

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.15A

Notes

The 'H' prefix in the Mullard/Philips naming convention indicates a 12.6 V heater tube.
Tentative/preliminary data (Vorlaufige Daten) per original Philips datasheet.
Triode and heptode sections share a common cathode.
Sams substitution guide lists 12AJ7 as substitute.
Brans lists equivalents: 12AJ8, 19AJ8, 19D8, 10C14, 6AJ8, 6C12, ECH81.

Pin Layout — Noval

1Heptode Anode

2Heptode Screen Grid (g2+g4)

3Common Cathode

Socket-Compatible Tubes ⚠ Not electrically compatible

References