179003TB Picture Monitor Tube
The 179003TB (also designated as 1790/03TB) is a 17-inch rectangular picture monitor tube designed primarily for use in television monitoring equipment. It features a metal-backed screen, low-voltage electrostatic focusing, and magnetic deflection. The tube is designed to be mounted in any position.
Physical Construction and Screen Characteristics
The 179003TB is constructed with a rectangular glass envelope and a metal-backed screen. The screen has a nominal 17-inch diagonal and a 90° deflection angle. The standard phosphor configuration is Type 'T' (Silver Activated), which provides white fluorescence, though other phosphors can be supplied upon request.
An external conductive coating is applied to the envelope, which may be utilized for Extra High Tension (E.H.T.) smoothing. The physical dimensions of the tube are as follows:
- Maximum Overall Length: 420 mm (with drawing specifications indicating 410 ± 10 mm)
- Nominal Neck Diameter: 37 mm (with drawing specifications indicating 36.5 ± 1.5 mm)
- Width: 390.5 ± 3.5 mm
- Height: 311 ± 3.5 mm
- Diagonal: 422 ± 3.5 mm
The useful screen area is defined by the following minimum dimensions:
- Minimum Width: 382 mm
- Minimum Height: 273 mm
- Minimum Diagonal: 390 mm
The tube utilizes a B12A (Duodecal) base for electrical connections and a CT8 cavity-type anode cap for the high-voltage connection.
Heater Ratings and Pinout Configuration
The 179003TB is equipped with an indirectly heated cathode. The nominal heater ratings are:
- Heater Voltage: 6.3 V
- Heater Current: 0.3 A
The B12A Duodecal base connections, viewed from the bottom of the tube, are assigned as follows:
Electrical Ratings and Operating Conditions
The electrical limits and typical operating parameters of the 179003TB are structured around its multi-anode electrostatic focusing system.
Absolute and Design-Maximum Ratings
These ratings represent the limiting values for safe and reliable operation of the tube:
- First Anode (A1) Voltage: 200 V (minimum) to 500 V (maximum)
- Second and Fourth Anode (A2 + A4) Voltage: 12 kV (minimum) to 18 kV (maximum)
- Third Anode (A3) Voltage: -500 V (maximum negative) to +500 V (maximum positive)
- Maximum Heater-to-Cathode Voltage (Vh-k): 200 V
- Maximum Grid-to-Cathode Resistance (Rg-k): 1.5 MΩ
- Maximum Heater-to-Cathode Resistance (Rh-k): 1.0 MΩ
Typical Operating Points
Under typical operating conditions, the tube is configured with the following electrical values:
- Heater Voltage: 6.3 V
- First Anode (A1) Voltage: 300 V
- Second and Fourth Anode (A2 + A4) Voltage: 15 kV
- Third Anode (A3) Focus Voltage: -300 V to +300 V (the optimum focus point lies within this range)
- Grid Voltage (Vg) for Visual Cut-off: -30 V to -90 V
During operation, the modulator (grid) must never be allowed to become positive with respect to the cathode. The single exception to this rule is immediately after switching off the equipment, at which point the modulator voltage may be permitted to rise to a maximum of +1 V.
Interelectrode Capacitances
The direct interelectrode capacitances of the 179003TB are specified as follows:
- Cathode to all other electrodes (Ck-all): Less than 8 pF
- Grid to all other electrodes (Cg-all): Less than 8 pF
- Anode to external conductive coating (Ca-ext. coating): Approximately 1500 pF
The capacitance between the anode and the external conductive coating provides the capacitance necessary for E.H.T. smoothing when the coating is grounded.
Technical Summary
The 179003TB is a specialized 17-inch rectangular picture monitor tube designed for television monitoring applications. It features a 90° deflection angle, magnetic deflection, and low-voltage electrostatic focusing via a third anode adjustable from -300 V to +300 V. Operating with a 6.3 V, 0.3 A heater, the tube utilizes a B12A Duodecal base and a CT8 cavity anode cap. With design-maximum ratings supporting an anode potential up to 18 kV and an integrated external conductive coating for E.H.T. smoothing, the 179003TB provides a robust display solution for professional monitoring environments.
