TUBEOFILE
40 — Small Signal Triode, UX4 | Tubeofile | Tubeofile
← Browse Medium quality — at least 60% of universal parameters and pins are present, but some key data is missing. Verify specific values against datasheets before critical use.
Known Equivalents & Substitutes
240 340 440 VT-40 CV2501
Similar Tubes (Not Drop-In Compatible)
Same UX4 base and identical 5V/0.25A filament but much lower mu (8 vs 30) and lower ra (10000 vs 150000 Ohm); general-purpose triode vs high-mu detector DHT detector/amplifier triode with same UX4 base but 2V battery filament and lower mu (~9.3 vs 30) Electrical Specifications
Absolute Maximum
Anode Voltage (max) Plate Voltage (max) 180V
Typical Operating
Anode Voltage (typical) Plate Voltage (typical) 180V
Grid 1 Bias Voltage Grid Bias -3V
Anode Current Plate Current 0.2mA
Notes
DHT tube: the filament serves as the cathode; there is no heater-cathode isolation. Very high plate resistance (150000 Ohm) and low plate current (0.2mA) — requires careful circuit design and high-impedance plate loads. GE Essential Characteristics: Va=180V, Vg=-3V, Ia=0.2mA, ra=150000 Ohm, gm=0.2 mA/V, mu=30. MIL-HDBK-213A lists this tube as VT-40. No Pa_max or Rg_max is specified on known datasheets. Va_max=180V per GE Essential 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
Anode Resistance Plate Resistance
150,000Ω
Transconductance Transconductance 0.2mA/V
Amplification Factor (μ) Amplification Factor 30—
Heater
Heater Voltage Filament Voltage 5V
Heater Current Filament Current 0.25A