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ECH4 — Triode-Hexode, P8A | Tubeofile
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ECH4
Triode-Hexode — P8A
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Philips
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Known Equivalents & Substitutes
ECH4N
Similar Tubes (Not Drop-In Compatible)
ACH1n
Heater variant — same structure but different heater specification
ECH21
Successor triode-hexode converter with Rimlock base — different pin configuration
ECH41
Successor with Rimlock base (1941) — same functional design, different construction
ECH81
Later Noval successor — same triode-hexode concept but completely different base and pinout
Electrical Specifications
Section 1 — Triode (Oscillator)
Typical Operating
Anode Voltage (typical)
Plate Voltage
100
V
Anode Current
Plate Current
6
mA
Transconductance
Transconductance
3.5
mA/V
Section 2 — Hexode (Mixer)
Absolute Maximum
Anode Voltage (max)
Max Plate Voltage
Notes
Uses the European side-contact P8A base — this is a spring-loaded contact system, not a pin system.
Predecessor was the ECH3; succeeded by the ECH21 (Rimlock) and ECH41.
ECH4N is a variant with different bulb shape but identical electrical characteristics.
Extensively used in European radio receivers from 1940-1950 with peak adoption around 1949.
The hexode section has three grids with the oscillator triode grid coupled to hexode grid 1.
Pin Layout — P8A
1
2
3
4
5
6
7
8
1
Hexode Plate
2
Hexode Screen Grid (g2)
3
Triode Grid
4
300
V
Screen Voltage (max)
Max Screen Voltage
150
V
Typical Operating
Anode Voltage (typical)
Plate Voltage
250
V
Anode Current
Plate Current
3.5
mA
Screen Voltage
Screen Voltage
100
V
Screen Current
Screen Current
5
mA
Anode Resistance
Plate Resistance
500,000
Ω
Transconductance
Conversion Transconductance
0.7
mA/V
Heater
Heater Voltage
Heater Voltage
6.3
V
Heater Current
Heater Current
0.35
A
Triode Plate
5
Heater
6
Cathode
7
Hexode Signal Grid (g1h)
8
Heater