Specialized - Cathode Ray ·CathodeRay
Direct-view cathode-ray picture tube documented by manufacturer data for type 16KP4A; available extracted technical detail is limited, so the description remains conservative.
The 16KP4A (also designated as 16KP4-A/16RP4-A) is a direct-view, all-glass cathode-ray picture tube designed for television receiver applications. It features a space-saving rectangular face shape, a spherical gray filter faceplate, and is designed for magnetic focus and deflection. The tube utilizes an electron gun configured for use with an external single-field ion-trap magnet.
The 16KP4A is identical to the 16KP4 except for its screen construction; the 16KP4A incorporates a reflective aluminized screen that significantly increases light output compared to the non-aluminized screen of the standard 16KP4.
The 16KP4A is constructed with a rectangular glass bulb (ASA designation J129B) and is designed to be mounted in any position. It features a high-quality gray filter faceplate with an approximate light transmission of 72 percent at the center, which improves picture contrast and detail under high ambient light conditions.
The outer surface of the cone is treated with an external conductive coating. When grounded, this coating acts as a filter capacitor in conjunction with the internal anode coating. The physical dimensions and mechanical limits of the tube are detailed below:
The bulb contact is a recessed small cavity cap (JETEC No. J1-21), and the base is a small-shell duodecal 5-pin (JETEC No. B5-57). The anode contact aligns with the Pin No. 6 position within a tolerance of ±30 degrees.
The 16KP4A utilizes a unipotential cathode with an indirectly heated filament. The nominal heater requirements and the interelectrode capacitances are as follows:
The tube uses the 12N basing arrangement, viewed from the bottom of the base:
The 16KP4A is designed to operate at high anode voltages to maintain brightness and focus quality. If the anode voltage falls below 12,000 Volts, both brightness and focus quality decrease. Typical operating parameters are documented under two distinct setups:
| Parameter | Operating Setup A | Operating Setup B |
|---|---|---|
| Anode Voltage | 12,000 Volts DC | 14,000 Volts DC |
| Grid No. 2 Voltage | 300 Volts DC | 300 Volts DC |
| Grid No. 1 Voltage (for visual extinction) | -33 to -77 Volts DC | -28 to -72 Volts DC |
| Focusing Coil Current (approximate) | 90 ± 20% mA DC | 108 mA DC |
| Ion-Trap Field / Current (approximate) | 75 ± 50% mA DC | 35 Gausses |
In Setup A, the focusing coil current is specified for a standard focus coil No. 109 (or equivalent) with the combined Grid No. 1 bias and video signal adjusted to produce a highlight brightness of 35 foot-lamberts on a 10 1/8" by 13 1/2" picture size. The distance from the reference line to the center of the air gap on the focus coil is 3.0 inches.
In Setup B, the focusing coil current is specified for a RETMA focusing coil No. 109 positioned with a distance of 3 1/4 inches from the yoke reference line to the center of the air gap. The ion-trap field intensity of 35 Gausses is achieved using a single-field ion-trap magnet adjusted to its optimum position, equivalent to 35 milliamperes through a RETMA ion-trap magnet No. 117.
The reference line of the tube is determined by the plane of the upper edge of a standard reference-line gauge (RETMA No. 110) when resting on the cone.
The maximum ratings of the 16KP4A are established under the Design-Center system. Under this system, the tube can withstand normal variations in line voltage and associated components, provided the design-center values are not exceeded by more than ten percent.
To prevent damage and ensure stable operation, the cathode should be returned to one side or to the mid-tap of the heater transformer winding.
Additionally, if the 16KP4A is operated at voltages exceeding 16,000 Volts, X-ray radiation shielding may be necessary. This shielding is required to avert the potential danger of injury resulting from prolonged exposure at close range.
The 16KP4A is a 16-inch rectangular glass cathode-ray tube featuring magnetic focus, magnetic deflection, and a 70-degree diagonal deflection angle. It is characterized by its reflective aluminized screen, which distinguishes it from the standard 16KP4 by providing enhanced light output. Operating with a 6.3 V, 0.6 A heater, the tube requires an external single-field ion-trap magnet and a focusing coil for proper raster alignment and spot extinction. With an anode rating of up to 16,000 Volts DC and a maximum Grid No. 1 circuit resistance of 1.5 Megohms, the 16KP4A provides a reliable, high-contrast display solution for vintage television designs when operated within its design-center limits.
Small-shell Duodecal 5-contact CRT base
General specifications
Properties common to every published source and operating point.
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
1 physical section, each with unique specifications.
Section 1
CRT-specific anode/focus/deflection ratings retained as parameters rather than mapped to ordinary plate/screen fields.
Source-dependent data
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 01
Published operating points and test conditions from this source.
Maximum Anode Voltage
16000 V
Typical Anode Voltage
12000 V
Maximum Grid2 Voltage
410 V
Typical Grid2 Voltage
300 V
DeflectionAngleApproximate
70 degree
FocusingMethod
Magnetic
DeflectingMethod
Magnetic
PhosphorNumber
4
FluorescentColor
White
Persistence
Medium
Data set 02
Published operating points and test conditions from this source.
MAGNETIC FOCUS 8 DEFLECTION
8 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
HEATER
6.3 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
A IF THIS TUBE IS OPERATED AT VOLTAGES IN E%CE SS OF 16r 000 VOL TS r %-RAY RAOI ATI ON SHIELDING NAY — value 1
16 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
A IF THIS TUBE IS OPERATED AT VOLTAGES IN E%CE SS OF 16r 000 VOL TS r %-RAY RAOI ATI ON SHIELDING NAY — value 2
0 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC ANODE r
12000 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC 6R ID #2 VOLTAGE — value 1
6 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC 6R ID #2 VOLTAGE — value 2
2 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC 6R ID #2 VOLTAGE — value 3
300 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC GRID #i VOLTAGE C — value 1
33 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC GRID #i VOLTAGE C — value 2
77 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
DC FOCUSING COIL CURRENT D (APPROX.)
90 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
OC ION TRAP CURRENT STANDARD COIL #111 (APPROX.) — value 1
111 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
OC ION TRAP CURRENT STANDARD COIL #111 (APPROX.) — value 2
75 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
OC ION TRAP CURRENT STANDARD COIL #111 (APPROX.) — value 3
50 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
D FOR STANDARD FOCUS COIL f109r OR EOUIVAL EMT r WITH THE COMBINED GRID !1 BIAS VOLTAGE AND VIDEO
1 V
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
lj 1/2" PICTURE SIZE. DISTANCE FROM DEFERENCE LIME TO CENTER OF AIR GAP OX FOCUS COIL SN ALL BE — value 1
1
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
lj 1/2" PICTURE SIZE. DISTANCE FROM DEFERENCE LIME TO CENTER OF AIR GAP OX FOCUS COIL SN ALL BE — value 2
2
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
MAXIMUM DC 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 DC 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 #i CIRCUIT RESISTANCE
1.5 mA
Published CRT datasheet value; multiple values on a row represent the source table's separate conditions/limits.
Data set 03
Published operating points and test conditions from this source.
HeaterOrFilamentVoltageNominal
6.3 V
HeaterOrFilamentCurrentNominal
600 mA