13EM7 — Dissimilar Double Triode Vacuum Tube

The 13EM7 is a glass octal-type vacuum tube containing two dissimilar triode units in a single envelope. It is designed primarily for use in television receivers as a combined vertical-deflection oscillator and vertical-deflection amplifier. Unit No. 1 is a high-mu triode intended for vertical-deflection oscillator service, while Unit No. 2 is a low-mu triode designed for vertical-deflection amplifier service.

Construction, Physical Dimensions, and Pinout

The 13EM7 is constructed in a T-9 glass bulb with a short intermediate shell 8-pin octal base (JEDEC B8-58, outline JEDEC 9-37). The tube can be mounted and operated in any position.

Physical Dimensions

• Maximum Diameter: 1.188 inches
• Maximum Seated Height: 2.313 inches
• Maximum Overall Height: 2.875 inches

Heater Characteristics

The tube features a coated unipotential cathode. The heater can be operated on either AC or DC.

• Heater Voltage: 13.0 V
• Heater Current: 0.45 A (450 mA)
• Average Heater Warm-up Time: 11 seconds

Basing and Pin Connections

The 13EM7 uses the 8BD basing diagram. The pin assignments, viewed from the bottom of the base, are as follows:

Unit No. 1 (the high-mu oscillator section) is connected to pins 4, 5, and 6. Unit No. 2 (the low-mu amplifier section) is connected to pins 1, 2, and 3.

Electrical Characteristics and Class A1 Operation

The two triode sections of the 13EM7 have highly dissimilar electrical characteristics, optimized for their respective roles as oscillator and power amplifier.

Direct Interelectrode Capacitances

The approximate direct interelectrode capacitances, measured without an external shield, are:

Class A1 Amplifier Characteristics

At typical operating points, the characteristics of each section are as follows:

Additional Operating Points and Knee Values

• Unit No. 1 Low-Current Cutoff: The grid voltage required to reduce the plate current to 10 µA is approximately -5.5 V.
• Unit No. 2 Low-Current Cutoff: The grid voltage required to reduce the plate current to 100 µA is approximately -45 V.
• Unit No. 2 Plate Current at -28 V Grid Bias: Approximately 10 mA.
• Unit No. 2 Instantaneous Plate Knee Values: At a plate voltage of 60 V and zero grid voltage, the plate current is 95 mA.

Maximum Ratings and Circuit Values

The maximum ratings are interpreted according to the Design-Maximum System (except where noted as Design-Center or Absolute Maximum) for operation in a 525-line, 30-frame television system.

Vertical-Deflection Service Ratings

Note on Pulse Ratings: For the peak pulse ratings, the pulse duration must not exceed 15% of a vertical scanning cycle (equivalent to 2.5 milliseconds in a standard system).

Heater-Cathode Voltage Limits

• Heater Negative with Respect to Cathode:
  • Maximum Total DC and Peak: 200 V
• Heater Positive with Respect to Cathode:
  • Maximum DC: 100 V
  • Maximum Total DC and Peak: 200 V

Circuit Considerations

In stages operating with grid-leak bias, an adequate cathode bias resistor or other suitable means is required to protect the tube in the absence of excitation.

Related Designations and Comparisons

The 13EM7 is part of a family of dissimilar double triodes. It shares identical internal structures and electrical characteristics with the 6EM7 (which uses a 6.3 V, 0.925 A heater) and the 10EM7 (which uses a 9.7 V, 0.6 A heater).

Additionally, the designation 13EM7/15EA7 or 13EM7/15EAY represents the same 13.0 V heater device, where the "15EA7" or "15EAY" suffix reflects alternative nomenclature for the same electrical and physical structure.

For the average plate characteristics of Unit No. 1, reference is made to the characteristics of Unit No. 1 of the 6DR7 (or 13DR7), which shares similar high-mu triode behavior.

Technical Summary

The 13EM7 is an octal-based, dissimilar double triode designed for television vertical-deflection circuits. It integrates a high-mu oscillator triode (Unit No. 1: mu ≈ 64–68, gm ≈ 1,600 µmhos) and a low-mu power amplifier triode (Unit No. 2: mu ≈ 5.4, gm ≈ 7,200 µmhos, plate dissipation ≤ 10 W) within a single T-9 envelope. Operating with a 13.0 V, 450 mA heater, the 13EM7 provides a compact, single-tube solution for generating and amplifying vertical deflection signals in television receivers.