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841 — Power Triode, UX4 | Tubeofile
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841
Power Triode — DHT — UX4
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RCA
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↗ Radiomuseum
Known Equivalents & Substitutes
VT-51
Similar Tubes (Not Drop-In Compatible)
801A
Same UX4 base and similar filament voltage (7.5V vs 6.5V), higher Pa_max (20W vs 15W); not a drop-in replacement due to different filament requirements
843
Same Pa_max (15W) and Va_max (450V) transmitting triode but different filament (2.5V/2.5A) and UY5 base; not pin-compatible
Electrical Specifications
Absolute Maximum
Anode Voltage (max)
Plate Voltage (max)
450
V
Anode Dissipation (max)
Plate Dissipation (max)
15
W
Cathode Current (max)
Plate Current (max)
60
mA
Typical Operating
Anode Voltage (typical)
Plate Voltage (typical, Class A)
425
V
Grid 1 Bias Voltage
Grid Voltage (Class A)
-40
V
Anode Current
Plate Current (Class A)
18
mA
Anode Resistance
Plate Resistance
9,600
Ω
Transconductance
Transconductance
Capacitances
Grid-to-Plate Capacitance
Grid-to-Plate Capacitance
3.7
pF
Grid-to-Cathode Capacitance
Grid-to-Filament Capacitance
2.6
pF
Anode-to-Cathode Capacitance
Plate-to-Filament Capacitance
1.4
pF
Heater
Heater Voltage
Filament Voltage
6.5
V
Heater Current
Filament Current
1.25
A
Notes
DHT tube: the thoriated tungsten filament serves as the cathode; there is no heater-cathode isolation.
Maximum plate current is 60 mA.
Designed primarily for RF oscillator and Class A amplifier service at plate voltages up to 450V.
Class A amplifier at Va=425V: Vg=-40V, Ia=18mA, mu=25, gm=2.6 mA/V, ra=9600 Ohm.
Filament may be operated on AC or DC. When AC-operated, grid bias voltage is referenced to filament midpoint.
Pin Layout — UX4
1
2
3
4
1
Filament +
2
Plate
3
Grid
4
Filament -
Socket-Compatible Tubes
⚠ Not electrically compatible
12A
26
2A3
30
300B
31
40
45
50
71A
801A
842
845
UX112A
UX199
References
https://frank.pocnet.net/sheets/049/8/841.pdf
https://tdsl.duncanamps.com/show.php?des=841
https://www.radiomuseum.org/tubes/tube_841.html
2.6
mA/V
Amplification Factor (μ)
Amplification Factor
25
—
VT-25
VT-52