Data: MediumMedium 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.
Contemporary DHT triode on UX4 base with 5V filament, similar mu (8) but higher ra (15000 Ω) and lower gm — used in similar applications but different operating characteristics
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Max Plate Voltage180V
Typical Operating
Anode Voltage (typical)Plate Voltage135V
Grid 1 Bias VoltageGrid Voltage-9V
Anode CurrentPlate Current6.2mA
Notes
One of the earliest oxide-coated filament triodes, introduced in the mid-1920s. The 112A superseded the original type 112 with improved characteristics.
The UX prefix denotes the UX4 base; later manufacturing dropped the prefix, designating it simply as 112A or 12A.
Cunningham marketed the same tube as CX-112-A.
Filament may be operated from a 6V storage battery with a suitable series resistor to reduce voltage to 5.0V at the socket terminals.
As a detector: recommended plate voltage 45V with grid leak and condenser bias. Grid leak 0.25 to 5 MΩ with 0.00025 µF grid condenser.
As an amplifier at Va=135V: Pout=115 mW into 8700 Ω load. At Va=180V (max): Pout=260 mW into 10800 Ω load.
When substituted for the 01A in radio-frequency circuits, neutralizing condensers or grid suppressor resistors may need adjustment to prevent oscillation.
Pin Layout — UX4
1Filament (f+)
2Plate
3Grid
4Filament (f-)
Socket-Compatible Tubes ⚠ Not electrically compatible