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845 — Power Triode, UX4 | Tubeofile
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845
Power Triode — DHT — UX4
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RCA
↗ Radiomuseum
Known Equivalents & Substitutes
UV845
VT-43
CV735
545
C845
38145
845W
R845
T845
Similar Tubes (Not Drop-In Compatible)
284A
WE transmitting triode listed as similar to 845 in RCA interchange guide; different filament and operating conditions
384D
WE transmitting triode listed as similar to 845 in RCA interchange guide; not pin-compatible
945
Transmitting triode listed as similar to 845 in RCA interchange guide
Electrical Specifications
Absolute Maximum
Anode Voltage (max)
Plate Voltage (max)
1,250
V
Anode Dissipation (max)
Plate Dissipation (max, ICAS)
100
W
Cathode Current (max)
Plate Current (max)
150
mA
Typical Operating
Anode Voltage (typical)
Plate Voltage (typical, Class A1)
1,000
V
Notes
DHT tube: the thoriated tungsten filament serves as the cathode; there is no heater-cathode isolation.
Graphite anode permits 100W plate dissipation (ICAS). CCS rating is 75W.
Class A1 amplifier at Va=1000V: Vg=-98V, Ia=65mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=5600 Ohm, Po=15W.
Class A1 amplifier at Va=1250V: Vg=-123V, Ia=80mA, mu=5.3, gm=3.1 mA/V, ra=1700 Ohm, rl=6600 Ohm, Po=23W.
Class B audio push-pull (2 tubes): Va=1000V, max-signal Ia per tube=120mA, Po=50W; Va=1250V, max-signal Ia=150mA, Po=78W.
The 845W is the ruggedised variant with identical electrical characteristics.
Pin Layout — UX4
1
2
3
4
1
Filament (f-)
2
Plate (Anode)
3
Grid
4
Filament (f+)
Socket-Compatible Tubes
⚠ Not electrically compatible
12A
26
2A3
30
300B
31
40
45
50
71A
801A
841
842
UX112A
UX199
References
https://frank.pocnet.net/sheets/049/8/845.pdf
https://www.radiomuseum.org/tubes/tube_845.html
Grid 1 Bias Voltage
Grid Voltage (Class A1, Va=1000V)
-98
V
Anode Current
Plate Current (Class A1, Va=1000V)
65
mA
Anode Resistance
Plate Resistance
1,700
Ω
Transconductance
Transconductance
3.1
mA/V
Amplification Factor (μ)
Amplification Factor
5.3
—
Output
Output Power
Output Power (Class A1, Va=1000V)
15
W
Load Impedance
Load Resistance (Class A1, Va=1000V)
5,600
Ω
Capacitances
Grid-to-Plate Capacitance
Grid-to-Plate Capacitance
6.5
pF
Input Capacitance
Input Capacitance
7.5
pF
Output Capacitance
Output Capacitance
3.3
pF
Heater
Heater Voltage
Filament Voltage
10
V
Heater Current
Filament Current
3.25
A
VT-25
VT-52