13P1S Output Beam Tetrode

The 13P1S (also designated as 13П1С) is an octal-base output beam tetrode designed primarily for the amplification of low-frequency power. It features an indirectly heated oxide-coated cathode and is housed in a glass envelope. The tube is engineered to withstand demanding environmental and mechanical conditions, making it suitable for applications requiring high reliability.

Mechanical Construction and Pinout

The 13P1S is enclosed in a glass bulb with a standard octal base. It has a maximum weight of 50 grams. The physical dimensions of the tube are characterized by a maximum overall height of 92 mm and a maximum bulb diameter of 33 mm. The base pins have a diameter of 2.4 ± 0.1 mm, and the central key (spigot) has a maximum diameter of 8 mm.

The tube is designed to operate reliably under severe environmental conditions, including:

• Ambient temperatures ranging from -60 °C to +70 °C.
• Relative humidity levels of 95% to 98% at an ambient temperature of +20 °C.
• Mechanical vibration loads up to 2.5 g.

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

• Pin 2: Heater (h)
• Pin 3: Anode and Grid 3 (a, g3) - internally connected
• Pin 4: Grid 2 / Screen Grid (g2)
• Pin 5: Grid 1 / Control Grid (g1)
• Pin 7: Heater (h)
• Pin 8: Cathode (k)

Electrical Characteristics and Typical Operation

The 13P1S operates with a nominal heater voltage of 13 V. The heater current is rated at 750 ± 80 mA.

Heater Power Calculation: Using the nominal heater voltage ($U_h = 13\text{ V}$) and the nominal heater current ($I_h = 0.75\text{ A}$), the nominal heater power consumption is calculated as: $P_h = 13\text{ V} \times 0.75\text{ A} = 9.75\text{ W}$

Under typical static operating conditions, the electrical characteristics of the 13P1S are defined as follows:

• Anode Voltage ($U_a$): 26 V
• Grid 2 Voltage ($U_{[g2](/tubes/G2)}$): 26 V
• Grid 1 Voltage ($U_{g1}$): 0 V
• Anode Current ($I_a$): 42 ± 10 mA
• Grid 2 Current ($I_{[g2](/tubes/G2)}$): \u2264 4 mA
• Transconductance ($S$): 7.5 ± 1.5 mA/V
• Internal Resistance ($R_i$): 1.5 k\u2126

The interelectrode capacitances of the device are:

• Input Capacitance (Grid 1 to Cathode, $C_{g1k}$): 15.5 ± 2.5 pF
• Output Capacitance (Anode to Cathode, $C_{ak}$): 13.0 ± 2.5 pF
• Feedback Capacitance (Grid 1 to Anode, $C_{g1a}$): \u2264 2.5 pF

Operating Points and Power Amplification

The 13P1S is rated for both single-ended (single-cycle) and push-pull low-frequency power amplifier configurations. The specific operating points and performance metrics for these configurations are detailed below.

Single-Ended (Single-Cycle) Operation

Under single-ended operating conditions, the tube is configured with:

• Anode Load Resistance ($R_a$): 750 \u2126
• Input AC Grid Voltage ($U_{g1\sim\text{eff}}$): 5.5 V
• Minimum Output Power ($P_k$): \u2265 220 mW

Push-Pull Operation

For push-pull configurations utilizing two 13P1S tubes, two distinct operating conditions are established:

• Condition 1 (Power Output): At an input AC grid voltage ($U_{g1\sim\text{eff}}$) of 11 V and an anode load resistance ($R_a$) of 1.5 k\u2126, the push-pull stage delivers an output power ($P_k$) of 550 mW.
• Condition 2 (Distortion Limit): At an input AC grid voltage ($U_{g1\sim\text{eff}}$) of 8.5 V and an anode load resistance ($R_a$) of 1.5 k\u2126, the push-pull stage operates with a distortion factor ($k_f$) of \u2264 10%.

Maximum and Minimum Permissible Ratings

To ensure the reliability and guaranteed service life of 2000 hours, the operating conditions of the 13P1S must be maintained within the following absolute limits:

Analysis of Characteristic Curves

The electrical behavior of the 13P1S is further illustrated by its family of characteristic curves, which detail the relationships between electrode voltages and currents.

Plate Characteristics ($I_a, I_{g2} = f(U_a)$)

The plate characteristic curves are plotted at a nominal heater voltage ($U_h$) of 13 V and a screen grid voltage ($U_{[g2](/tubes/G2)}$) of 26 V. These curves display the anode current ($I_a$, represented by solid lines) and screen grid current ($I_{[g2](/tubes/G2)}$, represented by dashed lines) as a function of anode voltage ($U_a$) across a range of control grid bias voltages ($U_{g1}$) from 0 V down to -10 V in steps of 2 V.

• At $U_{g1} = 0\text{ V}$, the anode current rises rapidly as anode voltage increases from 0 V, demonstrating low knee voltage characteristics before transitioning into a flatter, pentode-like plate resistance region.
• As the control grid bias ($U_{g1}$) becomes more negative, the overall anode current level decreases progressively.
• The screen grid current ($I_{[g2](/tubes/G2)}$) is highest at low anode voltages and decreases as the anode voltage rises, reflecting the partition of space charge between the screen grid and the anode.

Transfer Characteristics ($I_a, I_{g2} = f(U_{g1})$)

The transfer characteristics are plotted at a nominal heater voltage ($U_h$) of 13 V and a screen grid voltage ($U_{[g2](/tubes/G2)}$) of 26 V, for three distinct anode voltages ($U_a = 16\text{ V}$, $26\text{ V}$, and $36\text{ V}$).

• The curves show that anode current ($I_a$) increases as the control grid voltage ($U_{g1}$) moves from a negative bias toward 0 V.
• Higher anode voltages shift the transfer curve slightly upward, resulting in higher anode current for a given grid bias.
• The control grid cutoff voltage is approximately -12 V, where both anode and screen grid currents approach zero.

Technical Summary

The 13P1S is a robust, glass-envelope output beam tetrode featuring an octal base and an indirectly heated cathode. Operating with a nominal 13 V heater, it is optimized for low-voltage, low-frequency power amplification, delivering up to 220 mW in single-ended service and 550 mW in push-pull configurations. With a guaranteed service life of 2000 hours and high resistance to extreme temperatures, humidity, and mechanical vibration, the 13P1S is well-suited for reliable operation in demanding environments.