Specialized - Cathode Ray ·CathodeRay
Twelve-inch round P4 television picture tube with magnetic focusing and deflection. The gray-filter, aluminized screen and double-field ion-trap arrangement support high-contrast direct viewing at typical anode operation around 11 kV.
A 12-inch direct-viewed, round glass cathode-ray tube featuring magnetic deflection, magnetic focus, an aluminized screen, and a gray filter glass faceplate designed for monochrome television receivers.
The 12LP4C is a specialized television picture tube designed for direct-view applications. It utilizes magnetic deflection with an approximate deflecting angle of 54 degrees, alongside magnetic focusing. The tube incorporates an aluminized screen with P4 phosphor, which produces a white fluorescence with medium persistence. To enhance picture contrast under ambient lighting conditions, the tube features a gray filter glass faceplate with an approximate light transmittance of 74 percent. Additionally, the 12LP4C is designed to operate with an external, double-field type ion trap magnet and includes an external conductive coating that must be grounded during operation.
The 12LP4C is constructed with a round glass bulb envelope. The physical dimensions and mechanical features of the tube include:
The recessed small cavity cap, which serves as the anode contact, aligns with the vacant pin position No. 3 of the base within a tolerance of ±10 degrees. The reference line of the tube is determined by the plane of the upper edge of a standard JETEC No. 112 reference line gauge when the gauge is resting directly on the glass cone.
To facilitate proper circuit operation and shielding, the tube features an external conductive coating. This coating must be grounded. The capacitance formed between the external conductive coating and the internal anode ranges from a minimum of 750 µµF to a maximum of 3000 µµF.
The 12LP4C contains an indirectly heated cathode. The electrical requirements for the heater and the direct interelectrode capacitances are as follows:
| Parameter | Value |
|---|---|
| Nominal Heater Voltage | 6.3 V |
| Nominal Heater Current | 0.6 A (±10%) |
| Cathode to All Other Electrodes Capacitance | 5 µµF |
| Grid No. 1 to All Other Electrodes Capacitance | 6 µµF |
The 12N basing arrangement provides the following pin connections, viewed from the bottom of the base:
Under typical operating conditions, the 12LP4C is configured with the following parameters:
The specified focusing coil current of 110 mA DC is applicable when using a JETEC focusing coil 106 (or equivalent) positioned three and one-quarter inches from the reference line. This current is determined with the bias adjusted to 20 foot-lamberts on a 7 1/2 x 10 inch picture area sharply focused at the center of the screen.
The maximum ratings for the 12LP4C are established under the Design Center system. Operating the tube beyond these limits can result in degraded performance or permanent damage.
| Parameter | Maximum Rating |
|---|---|
| Anode Voltage | 12,000 V DC |
| Grid No. 2 Voltage | 410 V DC |
| Grid No. 1 Negative Bias Value | 125 V DC |
| Grid No. 1 Positive Bias Value | 0 V DC |
| Grid No. 1 Positive Peak Value | 2 V |
| Grid No. 1 Circuit Resistance | 1.5 MΩ |
The peak heater-cathode voltage limits are highly dependent on the polarity of the heater relative to the cathode and the operating state of the equipment:
When operating the 12LP4C, appropriate safety precautions must be taken regarding X-ray exposure. X-ray radiation shielding may be necessary to protect against the danger of personal injury from prolonged exposure at close range if the tube is operated at voltages higher than the maximum rated anode voltage of 12,000 Volts, or 16,000 Volts, whichever is less.
The 12LP4C is a 12-inch round glass television picture tube utilizing magnetic deflection and magnetic focus. It features a 6.3 V, 0.6 A heater, a small shell duodecal 5-pin base with a 12N basing configuration, and a recessed small cavity cap for the high-voltage anode connection. The tube is characterized by an aluminized P4 screen producing white fluorescence, a gray filter glass faceplate with 74% transmittance, and an external conductive coating that must be grounded. It is rated for a maximum anode voltage of 12,000 V DC and typically operates at 11,000 V DC with a Grid No. 2 voltage of 250 V DC, requiring an external double-field ion trap magnet of approximately 35 Gausses and a focusing coil current of approximately 110 mA DC.
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
Published maximum ratings and characteristics promoted semantically from the approved source.
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 Plate Voltage
12000 V
Typical Anode Voltage
11000 V
Phosphor
P4
Focusing Method
Magnetic
Deflecting Method
Magnetic