1266 — Cold-Cathode Voltage Regulator Tube

A cold-cathode, gas-filled voltage regulator tube designed for stable voltage control in electronic circuits.

Overview and Application

The 1266 is a Sylvania cold-cathode voltage regulator tube designed to maintain a stable potential of 70 volts across its operating range. As a cold-cathode device, it operates without a heater or filament, eliminating the need for a heater power supply and avoiding heater-to-cathode voltage limitations.

The electrical characteristics and application of the 1266 are very similar to those of the standard 0B3/VR90 voltage regulator tube. It is primarily used in applications requiring a constant, regulated DC voltage source.

Physical Specifications and Mounting

The physical construction of the 1266 is characterized by a glass envelope and an octal base. The manufacturer specifies the following physical parameters:

• Bulb Type: T-9
• Base Type: Intermediate Octal 6-Pin
• Maximum Overall Length: 3 5/16 inches
• Maximum Seated Height: 2 3/4 inches
• Mounting Position: Any position

The "Any" mounting position specification provides flexibility in mechanical layout, allowing the tube to be oriented horizontally, vertically, or at any angle within the equipment chassis.

Pinout and Basing Configuration

The 1266 utilizes the 4AJ-0-0 basing arrangement. The bottom-view diagram indicates the following pin assignments and internal connections:

• Pin 1: No Connection (NC)
• Pin 2: Cathode (K)
• Pin 3: No Connection (NC)
• Pin 4: No Connection (NC)
• Pin 5: Anode (A)
• Pin 7: Jumper (J)
• Pin 8: Jumper (J)

The diagram omits Pin 6. Although the physical base is designated as an "Intermediate Octal 6 Pin" type, the basing diagram details seven pin positions (Pins 1, 2, 3, 4, 5, 7, and 8). Pins 7 and 8 are connected internally via a jumper, which is noted as "Jumper not used" in standard applications.

Technical Summary

The 1266 is an intermediate octal, cold-cathode voltage regulator tube housed in a T-9 glass bulb. It regulates at a nominal 70 volts and shares functional similarity with the 0B3/VR90. The tube features a 4AJ-0-0 basing configuration with the cathode on Pin 2, the anode on Pin 5, and an internal jumper across Pins 7 and 8. It can be mounted in any position.