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Rectifier - Damper Diode ·Rectifier

12DW4A

Novar half-wave vacuum rectifier designed as a damper tube in television horizontal-deflection circuits.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
9HP
Socket code
-
Base pins
9
Nominal heater
12.6 V / 600 mA

Description

12DW4A — Half-Wave Vacuum Rectifier

The 12DW4A is a Novar-type half-wave vacuum rectifier designed specifically for service as a damper diode in the horizontal-deflection circuits of both color and black-and-white television receivers. It is engineered to handle high-voltage pulses and significant power dissipation typical of television scanning systems.

Construction, Physical Specifications, and Basing

The 12DW4A is constructed with a Novar T-9 glass envelope and utilizes a Novar Button 9-Pin base (E9-75 designation). The physical dimensions of the tube are as follows:

  • Maximum Diameter: 1.188 inches
  • Maximum Seated Height: 3.030 inches
  • Maximum Overall Height: 3.410 inches

The tube utilizes the 9HP basing arrangement. The pin connections, viewed from the bottom of the tube, are assigned as follows:

  • Pin 1: Internal Connection (IC)
  • Pin 2: Plate (P)
  • Pin 3: Internal Connection (IC)
  • Pin 4: Heater (H)
  • Pin 5: Heater (H)
  • Pin 6: Internal Connection (IC)
  • Pin 7: Plate (P)
  • Pin 8: Internal Connection (IC)
  • Pin 9: Cathode (K)

Wiring and Installation Precautions

Because the 12DW4A operates under high-voltage conditions, specific circuit layout and installation rules must be observed:

  • Socket terminals 1, 3, 6, and 8 must not be used as tie points for other circuit connections.
  • It is highly recommended to remove the socket clips corresponding to pins 1, 3, 6, and 8 to minimize electrical leakage and reduce the risk of high-voltage arc-over.
  • As a power-handling device, the tube generates significant heat during operation and must be provided with adequate ventilation.

Heater Characteristics

The 12DW4A features an indirectly heated cathode with a heater designed for series or parallel AC/DC operation. Its heater specifications are:

  • Heater Voltage: 12.6 V
  • Heater Current: 0.6 A (600 mA)
  • Average Heater Warm-up Time: 11 seconds

Family Comparisons

The 12DW4A belongs to a family of identical electrical designs that differ primarily in their heater configurations:

  • 6DW4A: Operates with a heater voltage of 6.3 V and a current of 1.2 A (1200 mA).
  • 17DW4A: Operates with a heater voltage of 16.8 V and a current of 450 mA (0.45 A), with an average warm-up time of 11 seconds.
  • 6DW4B: Shares the 6.3 V heater rating of the 6DW4A but features a shorter bulb (maximum seated height of 2.625 inches, maximum overall height of 3.005 inches) and an exhaust tip located on the base (E9-89 base).

Electrical Characteristics and Capacitances

Under typical operating conditions, the 12DW4A exhibits low internal resistance, which is critical for efficient damper service.

Tube Voltage Drop

The instantaneous tube voltage drop is a key measure of the rectifier's efficiency. For the 12DW4A, the instantaneous voltage drop is:

  • Voltage Drop: 25 V at a plate current of 350 mA.

Direct Interelectrode Capacitances

The capacitances of the tube are measured without an external shield (unshielded):

  • Heater to Cathode: 2.8 pF
  • Plate to Cathode and Heater: 6.5 pF
  • Cathode to Plate and Heater: 9.0 pF

Damper Service Ratings

The ratings of the 12DW4A are defined under the Design-Maximum Rating System. These limits are specified for operation in a standard 525-line, 30-frame television system.

Operating Limits

  • Maximum Peak Inverse Plate Voltage: 5500 V. This peak limit is subject to the condition that the pulse duration must not exceed 15% of a horizontal scanning cycle (equivalent to 10 microseconds in a standard system).
  • Maximum Plate Dissipation: 8.5 W.
  • Maximum Steady State Peak Current: 1300 mA.
  • Maximum DC Plate Current: 250 mA.

Heater-Cathode Voltage Ratings

The insulation between the heater and cathode is rated to withstand high potential differences, which is essential for damper service where the cathode often carries high-voltage pulses:

  • Heater Negative with Respect to Cathode:
    • Maximum DC Voltage: 900 V
    • Maximum Total DC and Peak Voltage: 5500 V
  • Heater Positive with Respect to Cathode:
    • Maximum DC Voltage: 100 V
    • Maximum Total DC and Peak Voltage: 300 V

(Note: While the 12DW4A and 6DW4A share these heater-cathode ratings, the related 6DW4B variant has a lower maximum peak negative heater-cathode voltage rating of -5000 V).

Technical Summary

The 12DW4A is a high-performance, Novar-based half-wave vacuum rectifier optimized for television damper service. Operating with a 12.6 V, 0.6 A heater, it provides robust power handling, including a maximum plate dissipation of 8.5 W and a peak inverse plate voltage rating of 5500 V. Its physical design features a Novar T-9 envelope with a 9HP pinout, requiring careful socket configuration (leaving pins 1, 3, 6, and 8 unused) to prevent high-voltage breakdown. With a low instantaneous voltage drop of 25 V at 350 mA, the 12DW4A delivers the high efficiency required for horizontal-deflection circuitry.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
9HP
Socket code
-
Base pins
9
Nominal heater voltage
12.6 V
Nominal heater current
600 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

9HP - Terminal pinout

Electrical assignments shared by every tube using this base designation.

TerminalSectionConnectionEvidence
PIN1Base Pin—IC

Original chart label IC; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN2Base Pin—P — Plate (Anode)

Original chart label P; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN3Base Pin—IC

Original chart label IC; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN4Base Pin—H — Heater

Original chart label H; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN5Base Pin—H — Heater

Original chart label H; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN6Base Pin—IC

Original chart label IC; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN7Base Pin—P — Plate (Anode)

Original chart label P; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN8Base Pin—IC

Original chart label IC; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

PIN9Base Pin—K — Cathode

Original chart label K; manufacturer verification pending

Unverified

EIA Base Connections printed p133, 9HP

Section ratings

1 physical section, each with unique specifications.

Section 1

Rectifier

X-ray radiationInterelectrode capacitances
Max plate dissipation
6 W
Rectifier peak inverse voltage
5000 V
Rectifier nominal output current
200 mA
Rectifier peak forward current
1.1 A
Rectifier forward voltage drop
12 V
Rectifier warm-up time
11 s

Promoted from published ratings/characteristics where directly applicable; additional published values retained in TUBE_SECTION_PARAMETER.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Rectifier

Other

  • Heater Voltage (ac/dc) 6-3 12.6

    16.8 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater Current 1-2 0.6

    450 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater Warm-up Time (Average) — 11

    11 seconds

    Published in approved 17DW4A target datasheet entry; Section1

  • Peak Inverse Plate Voltage*

    5000 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Peak Plate Current

    1100 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Average Plate Current

    200 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Peak value -f300 —

    -5000 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Average value +100

    900 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Tube Voltage Drop for plate current of

    140 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Tube Voltage Drop for plate current of 140 mA

    12 V

    Published in approved 17DW4A target datasheet entry; Section1

  • £ Pulse duration must not exceed 15% of a horizontal scanning cycle (

    10 microseconds

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater Voltage (ac/dc) 3.15 4.2

    6.3 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater Current 0.6 0.45

    300 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater Warm-up Time (Average) 11

    11 seconds

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate Voltage (Each Unit)

    300 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Peak positive value

    50 V

    Published in approved 17DW4A target datasheet entry; Section1

  • DC negative value

    50 V

    Published in approved 17DW4A target datasheet entry; Section1

  • DC positive value

    3 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.2 (Screen-Grid) Voltage

    150 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.l (Control-Grid) Voltage, Negative bias value

    50 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Cathode Current

    12 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate Dissipation (Each Unit)

    1.1 W

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.2 Input

    0.75 W

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate Voltage (Each Unit) 100

    100 V

    Published in approved 17DW4A target datasheet entry; Section1

Capacitance

  • Plate to Cathode and Heater

    6.5 pF

    Published in approved 17DW4A target datasheet entry; Section1

  • Heater to Cathode z

    8 pF

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid No. 3 to Plate (Each Unit)

    1.9 pF

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid No.l to All Other Electrodes

    6 pF

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid No.3 to All Other Electrodes (Each Unit)

    3.6 pF

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate to All Other Electrodes (Each Unit)

    3 pF

    Published in approved 17DW4A target datasheet entry; Section1

Characteristic

  • Grid-No-3 Voltage (Each Unit) —10

    0 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.2 Voltage 67.6

    67.5 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate Current (Each Unit)

    2.2 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.2 Current 6.5

    3.3 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Cathode Current 6.6

    7.8 mA

    Published in approved 17DW4A target datasheet entry; Section1

  • Plate Voltage 100

    100 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.3 Voltage 0

    0 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.2 Voltage 67.5

    67.5 V

    Published in approved 17DW4A target datasheet entry; Section1

  • Grid-No.3 Transconductance

    180 µS

    Published in approved 17DW4A target datasheet entry; Section1