17BW3 — Half-Wave Vacuum Rectifier and Damper Diode

A half-wave vacuum rectifier and damper diode designed for television horizontal-deflection circuits, featuring a duodecar construction and high-voltage insulation capabilities.

Overview

The 17BW3 is a half-wave vacuum rectifier and damper diode (heater-cathode diode) designed primarily for use in the horizontal-deflection circuits of television receivers. Constructed in a compactron T-9 glass envelope with a 12-pin button base, it is engineered to handle the high peak inverse voltages and peak currents typical of television damper service.

The 17BW3 belongs to a family of damper tubes that includes the 6BW3 and 22BW3. It is electrically identical to the 22BW3 except for its heater ratings, which are optimized for series-string heater chains requiring a 16.8 V supply at 0.6 A.

Construction and Physical Characteristics

The 17BW3 features a T-9 glass bulb envelope and a duodecar-type construction. It utilizes a 12-pin button base (E12-70) and requires a standard duodecar 12-contact socket. The physical dimensions of the tube are:

• Maximum overall height: 2.875 inches
• Maximum seated height: 2.500 inches
• Maximum diameter: 1.188 inches

The tube's internal structure is designed to minimize interelectrode capacitances and withstand high voltage gradients. The unshielded direct interelectrode capacitances are:

• Cathode to plate and heater: 8.5 pF
• Plate to cathode and heater: 6.0 pF
• Heater to cathode: 3.8 pF

Heater Ratings and Warm-up

The heater is designed for series or parallel operation, with a controlled warm-up time to ensure reliable operation in series-connected heater strings.

• Heater Voltage (AC/DC): 16.8 V
• Heater Current: 0.6 A (600 mA)
• Heater Warm-up Time: 11 seconds

Pinout and Base Connections

The 17BW3 uses the 12FX basing arrangement. There is a minor variation in documented pin assignments for the cathode and internal connections across different manufacturing specifications. The cathode is assigned to either Pin 6 or Pin 7, with the alternate pin designated as an internal connection (IC) that must not be used for external circuit wiring.

The complete pinout configuration is as follows:

• Pin 1: Heater (H)
• Pin 2: No Connection (NC)
• Pin 3: No Connection (NC)
• Pin 4: Internal Connection (IC)
• Pin 5: Internal Connection (IC)
• Pin 6: Cathode (K) or Internal Connection (IC)
• Pin 7: Internal Connection (IC) or Cathode (K)
• Pin 8: Internal Connection (IC)
• Pin 9: Internal Connection (IC)
• Pin 10: Plate (P)
• Pin 11: No Connection (NC)
• Pin 12: Heater (H)

Note: Pins designated as Internal Connection (IC) should not be used as tie points for external circuitry, as they may be connected to internal elements or support structures.

Damper Service Ratings and Operating Conditions

The 17BW3 is rated under the Design-Maximum Rating System for damper service in television receivers operating on a standard 525-line, 30-frame system. Under these conditions, the tube is subjected to high-voltage pulses during the horizontal retrace period.

Maximum Ratings

• Peak Inverse Plate Voltage: 5000 V (The pulse duration must not exceed 15% of one horizontal scanning cycle, equivalent to a maximum of 10 microseconds).
• Steady State Peak Plate Current: 1100 mA
• DC (Average) Plate Current: 175 mA
• Plate Dissipation: 6.5 W

Heater-Cathode Voltage Limits

Because the cathode of a damper tube in a horizontal-deflection circuit carries high pulse voltages, the heater-to-cathode insulation must withstand severe electrical stress. The maximum ratings are specified for both polarities:

• Heater Negative with Respect to Cathode:
  • DC Limit: 900 V
  • Total DC and Peak Limit: 5000 V
• Heater Positive with Respect to Cathode:
  • DC Limit: 100 V
  • Total DC and Peak Limit: 300 V

Typical Electrical Characteristics

The efficiency of a damper diode is largely determined by its internal voltage drop during conduction. The 17BW3 exhibits a low internal resistance, resulting in a low instantaneous voltage drop:

• Tube Voltage Drop (Instantaneous): 32 V, measured at an instantaneous plate current of 350 mA.

Technical Summary

The 17BW3 is a duodecar-type, half-wave vacuum rectifier designed specifically for television horizontal-deflection damper service. Operating with a 16.8 V, 0.6 A heater, it features a controlled 11-second warm-up time. It is capable of handling peak inverse voltages up to 5000 V and peak currents up to 1100 mA, with a maximum plate dissipation of 6.5 W. Its low instantaneous voltage drop of 32 V at 350 mA ensures efficient operation in demanding deflection circuits.