HCH81

Name: HCH81
Brand: Philips

Triode-Hexode — Noval — Philips

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Data: HighHigh quality — base, heater, all universal parameters present, and ≥50% of desirable parameters filled in. Safe to use for design decisions.

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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

ECH83

Reportedly identical internally to ECH81 — same base and pinout

UCH81

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)

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

6DS8 AL860 ECH81 ECH83 UCH81

References

https://frank.pocnet.net/sheets/030/h/HCH81.pdf

119V

Grid 1 Bias VoltageGrid 1 Bias Voltage-2.3V

Anode CurrentAnode Current3.7mA

Screen CurrentScreen Current (g2+g4)8.1mA

Anode ResistanceInternal Resistance1,000,000Ω

TransconductanceConversion Conductance (Sc)0.775mA/V

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.15A

,Suppressor Grid (g5)

4Heater

5Heater

6Triode Anode

7Heptode Signal Grid (g1)

8Triode Grid / Heptode Oscillator Grid (g3)

9Internal shield