10BP4 — Electromagnetic Cathode Ray Tube

An electromagnetic, direct-view cathode ray tube designed for black-and-white television applications, featuring magnetic focus and deflection, a 50-degree deflection angle, and a medium-persistence white screen.

Overview

The 10BP4 is a specialized cathode ray tube (CRT) designed for direct-view television receivers. It is engineered to produce a high-definition black-and-white picture with a nominal image size of 6 inches by 8 inches. The tube utilizes magnetic deflection and magnetic focusing, and it requires an external, magnetic ion-trap magnet to prevent screen blemishes.

Constructed with a glass bulb and a conductive external coating, the 10BP4 features a coated unipotential cathode and is designed to operate in any mounting position.

Physical and Constructional Specifications

The 10BP4 is built around a glass envelope with specific physical dimensions and screen characteristics optimized for early television displays.

Screen and Phosphor Characteristics

• Fluorescence: White
• Phosphorescence: White
• Persistence: Medium
• Deflection Method: Magnetic
• Focusing Method: Magnetic
• Deflection Angle (Approximate): 50 degrees
• Ion Trap: Magnetic (requires an external ion-trap magnet)
• External Coating: Conductive

Physical Dimensions

The physical envelope of the 10BP4 is defined by the following dimensions:

Heater and Basing Configuration

The 10BP4 is equipped with a small shell duodecal 7-pin base and an external anode cap. The heater is designed for either AC or DC operation.

Heater Characteristics

• Heater Voltage: 6.3 Volts
• Heater Current: 0.6 Ampere
• Cathode Type: Coated unipotential

Pin Connections

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

• Pin 1: Heater
• Pin 2: Grid No. 1
• Pin 6: No Connection
• Pin 7: No Connection
• Pin 10: Grid No. 2
• Pin 11: Cathode
• Pin 12: Heater
• Cap: Anode, Grid No. 3

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the tube are specified as follows:

• Grid #1 to all other electrodes (G1 to H + K + G2 + A & G3): 6.5 µµF
• Cathode to all other electrodes (K to H + G1 + G2 + A & G3): 5.0 µµF
• External conductive coating to Anode #2: 2500 µµF maximum, 500 µµF minimum

Maximum Ratings

The maximum ratings for the 10BP4 are interpreted according to the RMA Standard M8-210. Operating the tube beyond these limits may impair performance or cause permanent damage.

Typical Operating Conditions

Under typical operating conditions, the 10BP4 is configured with the following parameters:

• Anode Voltage: 9,000 Volts
• Grid #2 Voltage: 250 Volts
• Grid #1 Voltage (for visual extinction of undeflected focused spot): -27 to -63 Volts

Performance Curves and Characteristics

The operational performance of the 10BP4 is characterized by the relationship between the peak Grid #1 signal voltage, the resulting anode current, and the highlight brightness of the screen. These characteristics are measured under typical operating conditions of a 6.3 V heater, a 9,000 V anode supply, and a Grid #2 voltage of 250 V.

• Highlight Brightness: The highlight brightness (measured in foot-lamberts) rises non-linearly with the peak Grid #1 signal voltage. It begins to register above 0 foot-lamberts past a 10-volt peak signal, reaching approximately 50 foot-lamberts at a 30-volt peak signal, and climbing to 100 foot-lamberts at approximately 37 volts.
• Anode Current: The anode current (measured in microamperes) follows a similar upward curve. It remains near zero for low signal voltages, rising to approximately 200 microamperes at a 30-volt peak Grid #1 signal, and reaching approximately 500 microamperes at a 40-volt peak signal.

Technical Summary

The 10BP4 is a 10-1/2 inch electromagnetic cathode ray tube designed for direct-view black-and-white television receivers, producing a 6" by 8" picture. It features a small shell duodecal 7-pin base, a 6.3 V / 0.6 A heater, and requires external magnetic deflection, magnetic focusing, and an external ion-trap magnet. Operating typically with an anode voltage of 9,000 V and a Grid #2 voltage of 250 V, it provides high-definition images with a medium-persistence white phosphor screen.