10Z1L — Universal Pentode with a Short Characteristic Curve

The 10Z1L is a universal pentode designed for the amplification of voltage and power, as well as the generation of high-frequency oscillations at frequencies up to 200 MHz. It features a short grid characteristic curve and is engineered for reliable operation under demanding environmental and mechanical conditions.

Construction, Physical Dimensions, and Pinout

The 10Z1L is constructed with a glass bulb envelope and is equipped with an external metal screen to minimize electromagnetic interference. It features a flat base with a central locating key and an indirectly heated, oxide-coated cathode.

The physical dimensions of the device are characterized by:

• Maximum overall height: 69 mm
• Maximum seated height: 60 mm
• Top cap/shield diameter: 20 mm
• Maximum weight: 35 g

The tube is designed with an 8-pin base configuration. The pin connections, viewed from the bottom of the tube, are assigned as follows:

Electrical Characteristics and Operating Points

The nominal electrical characteristics of the 10Z1L are specified at a standard Class A operating point. Under these conditions, the heater is supplied with a nominal 10 V, and Grid 3 is held at ground potential.

Standard Operating Conditions and Parameters

The internal plate resistance (Ri) varies across production lots:

• For 80% of tubes: 0.9 M\u03a9
• For 20% of tubes: 0.5 M\u03a9

Cutoff and Power Output Characteristics

• Plate Cutoff Current (Iaz): When Grid 1 bias is increased to -7 V, the plate current drops to \u2264 100 \u03bcA.
• Output Power (Pk): The tube is capable of delivering an output power of \u2265 0.5 W under the following specific operating conditions:
  • Plate Voltage (Ua): 250 V
  • Grid 2 Voltage (Ug2): 250 V
  • Effective Input Signal Voltage (Ug1~eff): 2.8 V
  • Cathode Bias Resistor (Rk): 500 \u03a9
  • Plate Load Resistor (Ra): 35 k\u03a9
  • Grid 2 Resistor (Rg2): 20 k\u03a9

Interelectrode Capacitances

The capacitive coupling between the internal electrodes of the 10Z1L is kept low to facilitate high-frequency operation:

Permissible Ratings and Environmental Limits

To ensure reliable operation and achieve the guaranteed service life of 2500 hours, the operating conditions must be maintained within the following absolute maximum and minimum limits:

Environmental and Mechanical Durability

The 10Z1L is designed to withstand harsh environmental conditions and mechanical stress:

• Ambient Temperature Range: -60 \u00b0C to +70 \u00b0C
• Relative Humidity: 95% to 98% (measured at an ambient temperature of +20 \u00b0C)
• Vibration Resistance: Withstands vibration loads up to 2.5 g
• Impact Resistance: Withstands multiple impact loads up to 12 g

Characteristic Curves and Triode Connection

The electrical behavior of the 10Z1L is further illustrated by its characteristic curves under various operating configurations:

• Plate Characteristics (Ia vs. Ua): At a nominal heater voltage of 10 V, Grid 2 voltage of 75 V, and Grid 3 voltage of 0 V, the plate current (Ia) curves for Grid 1 voltages (Ug1) from 0 V to -4 V exhibit a classic pentode profile. The curves rise sharply at low plate voltages (below 30 V) and flatten out almost horizontally across the remainder of the voltage range up to 250 V, demonstrating high dynamic plate resistance.
• Grid 2 Current Characteristics (Ig2 vs. Ua): Under the same operating conditions, the Grid 2 current (Ig2) is highest when the plate voltage is near zero. As the plate voltage increases and begins to collect electrons, the Grid 2 current drops rapidly, stabilizing at a low level (typically below 2 mA) for plate voltages above 50 V.
• Transfer Characteristics (Ia, Ig2 vs. Ug1): At a plate voltage of 150 V and heater voltage of 10 V, the transfer curves show the relationship of plate and Grid 2 currents to the control grid bias. Curves plotted for Grid 2 voltages of 75 V and 100 V show a smooth reduction in both currents as the control grid bias becomes more negative, with plate current approaching complete cutoff near -6 V to -8 V.
• Triode-Connected Characteristics (Ia vs. Ua): When configured in a triode connection at a heater voltage of 10 V, the tube exhibits triode-like behavior. The plate current curves rise more steeply and continuously with increasing plate voltage. These curves are plotted for Grid 1 bias values ranging from 0 V down to -14 V, showing a wider bias range compared to the pentode mode.

Technical Summary

The 10Z1L is a robust, high-frequency universal pentode featuring an indirectly heated oxide-coated cathode, an integrated external metal shield, and a flat 8-pin base. Operating with a nominal 10 V heater supply, it is optimized for voltage and power amplification as well as high-frequency oscillation up to 200 MHz.

With a guaranteed service life of 2500 hours, the tube is highly resistant to extreme temperatures (-60 \u00b0C to +70 \u00b0C), high humidity, and mechanical shocks up to 12 g. Its electrical parameters include a transconductance of 1.7 mA/V, a plate resistance of 0.5 to 0.9 M\u03a9, and low interelectrode capacitances (such as a grid-to-plate capacitance of \u2264 0.01 pF), making it a highly stable and versatile choice for high-frequency and general-purpose amplification.