Tube-number record
X719 / ECH81
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BrandMarconi
ClassTriode-Heptode
BaseNoval (B9A)
Filament6.3 V @ 300 mA
Construction
Primary TypeIndirectly heated
EnvelopeTubular
SectionsTriode-Heptode
Filament / Heater
Heater NotesIndirectly heated
Absolute Maximum Ratings
Plate Voltage300 V
Plate Dissipation1.7 W
Grid 2 Voltage300 V
Grid 1 Voltage-1.3 V
Cathode Current12.5 mA
H-C Voltage100 V
Audio Performance
Key Features
- Indirectly heated
- Frequency changer
Typical Operation
| Mode | Plate V | Gm (µmhos) | Rp (Ω) | µ | Plate mA |
|---|---|---|---|---|---|
| Triode Section | 100 V | 3700 | — | 22 | 13.5 mA |
| Heptode Section as r.f. or i.f. Amplifier | 250 V | 2400 | 700000 | — | 6.5 mA |
| Heptode Section as a.m. Frequency Changer | 250 V | 775 | 1000000 | — |
Application Notes
Primarily designed for use as a frequency changer. Rg1-k is 3 megohms.
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