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16LP4A

Direct-view cathode-ray picture tube documented by manufacturer data for type 16LP4A; available extracted technical detail is limited, so the description remains conservative.

Directly heatedCold cathodeCommon cathodeDissimilarSpecialized

Sections: 1
Base: 12N
Socket code: DUODECAL5
Base pins: 5
Nominal heater: 6.3 V / 600 mA

Description

16LP4A — Direct-View Cathode-Ray Picture Tube

The 16LP4A (also designated as 16LP4-A) is an all-glass, direct-view cathode-ray picture tube designed primarily for television receiver applications. It features a 16-inch round glass envelope with a spherical faceplate, providing a nominal picture size of 14 1/2 inches by 10 7/8 inches (or a raster size of 10 1/4 inches by 14 1/2 inches) with rounded sides.

The tube utilizes magnetic focusing and magnetic deflection, a unipotential cathode, and an electron gun designed for operation with an external double-field ion-trap magnet. An external conductive coating is applied to the bulb, which serves as a high-voltage filter capacitor when connected to ground.

The 16LP4A is identical to the 16LP4 except for its faceplate construction. While the standard 16LP4 uses a clear faceplate, the 16LP4A incorporates a high-quality gray filter faceplate designed to enhance picture contrast and detail under high ambient light conditions.

Mechanical Specifications and Physical Dimensions

The 16LP4A is constructed with a round glass bulb (ASA designation J127C) and a spherical faceplate. The physical dimensions and mechanical limits of the tube are as follows:

Overall Length: 22 1/4 ± 3/8 inches
Greatest Diameter of Bulb: 15 7/8 ± 1/8 inches
Minimum Useful Screen Diameter: 14 1/2 inches
Neck Length: 7 3/8 inches
Approximate Net Weight: 17 1/2 pounds
Mounting Position: Any

Base and Terminal Connections

The tube is equipped with a small-shell duodecal 5-pin base (JETEC No. B5-57) and uses the 12N basing configuration. The high-voltage anode terminal is a recessed small cavity cap (JETEC No. J1-21) located on the side of the bulb cone.

The anode terminal aligns with the pin No. 3 position on the base, with an alignment tolerance of ±10 to ±30 degrees. The space along the neck (approximately 3 5/8 ± 1/16 inches from the base end) must be kept clear to accommodate the external ion-trap magnet.

The pin connections, viewed from the bottom of the base, are assigned as follows:

Pin Number	Connection
Pin 1	Heater
Pin 2	Grid No. 1
Pin 10	Grid No. 2
Pin 11	Cathode
Pin 12	Heater
Cap	Anode (Grid No. 3 / Anode)

Note: Grid No. 3 and the anode are connected internally within the tube and are collectively referred to as the anode.

Electrical and Optical Characteristics

Heater Ratings

The 16LP4A is designed for indirect heating of its unipotential cathode. The nominal heater operating parameters are:

Heater Voltage: 6.3 Volts (AC or DC)
Heater Current: 0.6 Amperes (with a tolerance of ±10%)

Direct Interelectrode Capacitances

The approximate direct interelectrode capacitances of the tube are:

Cathode to All Other Electrodes: 5 µµf (pF)
Grid No. 1 to All Other Electrodes: 6 µµf (pF)
External Conductive Coating to Anode (Maximum): 2,000 µµf (pF)
External Conductive Coating to Anode (Minimum): 750 µµf (pF)

The external conductive coating acts as a filter capacitor for the high-voltage anode supply when the coating is properly grounded.

Optical Characteristics

The faceplate of the 16LP4A is made of gray-tinted glass to improve contrast. The optical properties of the screen and faceplate include:

Phosphor Number: P4 (Sulfide type)
Fluorescent Color: White
Phosphorescent Color: White
Persistence: Short to Medium
Faceplate Light Transmission at Center: Approximately 66% to 73%

Maximum Ratings (Design-Center Values)

The following maximum ratings are established under the design-center system. These ratings represent limits that the tube can withstand under normal variations in line voltage and component tolerances, provided the design-center values are not exceeded by more than ten percent. All voltages are measured with respect to the cathode.

Parameter	Maximum Rating	Unit
Anode Voltage	14,000	Volts DC
Grid No. 2 Voltage	410	Volts DC
Grid No. 1 Voltage (Negative-Bias Value)	125	Volts DC
Grid No. 1 Voltage (Positive-Bias Value)	0	Volts DC
Grid No. 1 Voltage (Positive-Peak Value)	2	Volts
Grid No. 1 Circuit Resistance	1.5	Megohms

Peak Heater-Cathode Voltage Limits

The maximum allowable peak voltage between the heater and the cathode depends on the polarity and operating state:

Heater Negative with Respect to Cathode:
- During warm-up period (not to exceed 15 seconds): 410 Volts DC
- After equipment warm-up / Normal operation: 125 Volts DC
Heater Positive with Respect to Cathode: 125 Volts DC

Typical Operating Conditions

Under typical operating conditions, the tube is operated at an anode voltage of 12,000 Volts DC. Brightness and focus quality decrease if the anode voltage is reduced; in general, the anode voltage should not be operated below 10,000 Volts.

The typical operating parameters are defined as follows:

DC Anode Voltage: 12,000 Volts
DC Grid No. 2 Voltage: 300 Volts
DC Grid No. 1 Voltage (for visual extinction of focused raster/spot): -28 to -77 Volts
Deflection Angle (Approximate): 52 Degrees

Focusing and Ion-Trap Magnet Requirements

The focusing and ion-trap systems require external magnetic fields, which are typically provided by standardized electromagnetic coils or permanent magnets:

Focusing Coil Current:
- Using standard focus coil No. 106 (or equivalent): Approximately 110 mA. This is specified with the combined Grid No. 1 bias and video signal adjusted to produce a highlight brightness of 20 foot-lamberts on a 10 1/4 inches by 14 1/2 inches picture size. The distance from the reference line to the center of the air gap on the focus coil is set to 3.25 inches.
- Using RETMA focusing coil No. 109: Approximately 97 mA. The distance from the yoke-reference-line to the center of the air gap on the focus coil is set to 3 1/2 inches.
Ion-Trap Magnet:
- Field Intensity: Approximately 35 Gausses (using a double-field ion-trap magnet adjusted to the optimum position).
- Current Equivalent: Equivalent to approximately 120 mA through a standard RETMA ion-trap magnet No. 108.

The reference line of the tube is determined by the plane of the upper edge of a reference-line gage (such as RETMA No. 112) when the gage is resting on the cone of the bulb.

Technical Summary

The 16LP4A is a 16-inch round, all-glass, magnetic-focus and magnetic-deflection cathode-ray picture tube featuring a 52-degree deflection angle and a unipotential cathode. It is designed with a gray-tinted spherical faceplate (66% to 73% light transmission) to optimize picture contrast under ambient light, distinguishing it from the clear-glass 16LP4.

Operating at a typical anode voltage of 12,000 V (with a design-center maximum of 14,000 V), the tube requires an external double-field ion-trap magnet and a focusing coil (such as RETMA No. 106 or No. 109) to achieve optimal spot focus and raster illumination. Its external conductive coating provides integrated high-voltage filtering (750 to 2,000 pF) when grounded, making it a self-contained solution for high-voltage stability in television receiver circuits.

Socket description

Small-shell Duodecal 5-contact CRT base

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 12N
Socket code: DUODECAL5
Base pins: 5
Nominal heater voltage: 6.3 V
Nominal heater current: 600 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

12N - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Cathode Ray

X-ray radiationInterelectrode capacitances

Max plate voltage: 4000 V
Max screen voltage: 41 V

CRT-specific anode/focus/deflection ratings retained as parameters rather than mapped to ordinary plate/screen fields.

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

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Other

Maximum Anode Voltage
14000 V
Typical Anode Voltage
12000 V
Maximum Grid2 Voltage
410 V
Typical Grid2 Voltage
300 V

Characteristic

DeflectionAngleApproximate
62 degree
FocusingMethod
Magnetic
DeflectingMethod
Magnetic
PhosphorNumber
4
FluorescentColor
White
Persistence
Medium

Data set 02

1966 Tung Sol Electronic Tubes 4 of 4

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Characteristics

E XTE P,NAL DOUBLE FIELD ION TRAP — value 1
4
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
E XTE P,NAL DOUBLE FIELD ION TRAP — value 2
1
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
E XTE P,NAL DOUBLE FIELD ION TRAP — value 3
2
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DEFLECTION ANGLE (APPROX.)
5 degrees
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
HEATER
6 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC GRID #2 VOLTAGE
2 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC FOCUSING COIL CURRENT (APPROX.J B
11 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC ION TRAP CURRENT STANDARD COIL #108 (APPROX.) — value 1
108 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC ION TRAP CURRENT STANDARD COIL #108 (APPROX.) — value 2
12 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
BFOR STANDARD FO LUS COIL 1106, OR EQUIVALENT. WITH THE COMBINED G0.1D W1 BIAS VOLTAGE 0.ND VI OEO — value 1
1106 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
BFOR STANDARD FO LUS COIL 1106, OR EQUIVALENT. WITH THE COMBINED G0.1D W1 BIAS VOLTAGE 0.ND VI OEO — value 2
0 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
SIGNAL VOLTAGE ADJUSTED TO PRODUCE A MIGNLI GHT BRIGHTNESS OF 20 FOOT LAM8ERT5 ON A 10 1/4" BT — value 1
10 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
SIGNAL VOLTAGE ADJUSTED TO PRODUCE A MIGNLI GHT BRIGHTNESS OF 20 FOOT LAM8ERT5 ON A 10 1/4" BT — value 2
1 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
SIGNAL VOLTAGE ADJUSTED TO PRODUCE A MIGNLI GHT BRIGHTNESS OF 20 FOOT LAM8ERT5 ON A 10 1/4" BT — value 3
4 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
14 1/2" PICTURE SIZE. DISTANCE FROM REFERENCE LI XE TO CENTER OF AIR GAP ON FOCUS COIL SHALL BE — value 1
14
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
14 1/2" PICTURE SIZE. DISTANCE FROM REFERENCE LI XE TO CENTER OF AIR GAP ON FOCUS COIL SHALL BE — value 2
1
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
14 1/2" PICTURE SIZE. DISTANCE FROM REFERENCE LI XE TO CENTER OF AIR GAP ON FOCUS COIL SHALL BE — value 3
2
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.

Other

MAXIMUM DC ANODE
4000 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
MAXIMUM OC GRID #2 VOLTAGE — value 1
2 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
MAXIMUM OC GRID #2 VOLTAGE — value 2
41 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
MAXIMUM GRID #1 VOLTAGE
1 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
MAXIMUM GRID #1 CIRCUIT RESISTANCE
1 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.

Data set 03

1968 General Electric Co

Published operating points and test conditions from this source.

SECTION 1

Cathode Ray

Other

HeaterOrFilamentVoltageNominal
6.3 V
HeaterOrFilamentCurrentNominal
600 mA