PL36 — Power Pentode, Octal | Tubeofile

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PL36

Power Pentode — Octal

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Philips

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Known Equivalents & Substitutes

25E5

Similar Tubes (Not Drop-In Compatible)

6CM5

American designation for EL36 — same electrical characteristics but 6.3V heater

EL36

Same electrical characteristics but 6.3V/1.25A parallel heater — not a drop-in in 300mA series-string circuits

PL81

Listed as equivalent in Brans — similar line-output pentode but different electrical characteristics

Electrical Specifications

Section 1 — Pentode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)250V

Screen Voltage (max)Screen Voltage (max)250V

Anode Dissipation (max)Anode Dissipation (max)12W

Screen Dissipation (max)Screen Dissipation (max)5W

Cathode Current (max)Cathode Current (max)

Notes

300mA series-string heater (25V/0.3A) for AC/DC TV receivers. The 'P' prefix in Mullard/Philips nomenclature denotes a 300mA heater string design.
Valve Equivalents database confirms I/O base (Octal with top cap), 25V heater (via 25E5 entry).
Philips interchange lists 25E5 as the American equivalent designation.
Brans Vademecum lists PL81 as equivalent — this is a similar line-output pentode but with different electrical characteristics (EL81-based vs EL36-based).
Electrically identical to EL36 in all electrode characteristics; only the heater differs.
Not interchangeable with EL36/6CM5 without heater circuit modification.

Pin Layout — Octal

1Internal Connection

2Internal Connection (Cathode/Suppressor)

3Heater

Socket-Compatible Tubes ⚠ Not electrically compatible

25E5 EL36

200mA

Heater-to-Cathode Voltage (max)Heater-to-Cathode Voltage (max)100V

Max Grid ResistorMax Grid Resistor0.5MΩ

Typical Operating

Anode Voltage (typical)Anode Voltage (typical)100V

Screen Voltage (typical)Screen Voltage (typical)100V

Grid 1 Bias VoltageGrid 1 Bias Voltage-8.2V

Anode CurrentAnode Current100mA

Screen CurrentScreen Current7mA

Anode ResistanceAnode Resistance5,000Ω

TransconductanceTransconductance14mA/V

Output

Output PowerOutput Power (Class B PP)44.5W

Load ImpedanceLoad Impedance (Class B PP)3,500Ω

Capacitances

Grid-to-Plate CapacitanceGrid-to-Plate Capacitance1.1pF

Grid-to-Cathode CapacitanceGrid-to-Cathode Capacitance17.5pF

Anode-to-Cathode CapacitanceAnode-to-Cathode Capacitance8pF

Section 2 — Triode Strapped

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)250V

Anode Dissipation (max)Anode Dissipation (max)13W

Cathode Current (max)Cathode Current (max)200mA

Typical Operating

Anode Voltage (typical)Anode Voltage375V

Anode CurrentAnode Current50mA

Anode ResistanceAnode Resistance800Ω

TransconductanceTransconductance6.8mA/V

Amplification Factor (μ)Amplification Factor (μ)5—

Output

Output PowerOutput Power (SE Class A)7.8W

Load ImpedanceLoad Impedance (SE Class A)6,400Ω

Heater

Heater VoltageHeater Voltage25V

Heater CurrentHeater Current0.3A

Internal Connection (Cathode/Suppressor)

5Screen Grid (g2)

6Control Grid (g1)

7No Connection

8Heater

TCTop Cap —Anode (Top Cap)