TUBEOFILE
AL3 — Power Pentode, P8A | Tubeofile
← Browse Philips Medium quality — at least 60% of universal parameters and pins are present, but some key data is missing. Verify specific values against datasheets before critical use.
Known Equivalents & Substitutes
TL3 TAL3 VAL3 TL34 UAL3
Similar Tubes (Not Drop-In Compatible)
Improved successor with profiled cathode (1936) — same P8A base, higher efficiency 6.3 V heater version — electrically identical but different heater voltage, not interchangeable 6.3 V heater improved version — different heater voltage Different base with slightly different data Electrical Specifications
Absolute Maximum
Anode Voltage (max) Anode Voltage (max) 250V
Screen Voltage (max) Screen Voltage (max) 275V
Anode Dissipation (max) Anode Dissipation (max) 9W
Typical Operating
Anode Voltage (typical) Anode Voltage 250V
Notes
The AL3 is the 4 V heater version of the EL3. 'A' prefix = 4 V heater in the Philips naming convention. Withdrawn and replaced by the AL4 (improved profiled cathode) in 1936. Anode connection via top cap. P8A side-contact base carries heater, cathode, grids, and metallization. Cathode-bias only — fixed bias is prohibited per the Philips datasheet. gm of 9 mA/V — significantly higher than earlier types (2.5 mA/V). Found in 86 radio models from 1935-1938. Pin Layout — P8A
1 2 3 4 5 6 7 8
1 Control Grid
2 Cathode
3 Heater
4
Socket-Compatible Tubes ⚠ Not electrically compatible
Screen Voltage (typical) Screen Voltage
250V
Grid 1 Bias Voltage Grid 1 Bias Voltage -6V
Anode Current Anode Current 36mA
Screen Current Screen Current 4mA
Anode Resistance Anode Resistance 50,000Ω
Transconductance Transconductance 9mA/V
Cathode Resistor (self-bias) Cathode Resistor (self-bias) 150Ω
Output
Output Power Output Power (Class A SE) 4.5W
Load Impedance Load Impedance 7,000Ω
Heater
Heater Voltage Heater Voltage 4V
Heater Current Heater Current 1.85A
Absolute Maximum
Anode Voltage (max) Anode Voltage (max) 250V
Screen Voltage (max) Screen Voltage (max) 275V
Anode Dissipation (max) Anode Dissipation (max) 9W
Typical Operating
Anode Voltage (typical) Anode Voltage (typical) 250V
Screen Voltage (typical) Screen Voltage (typical) 250V
Grid 1 Bias Voltage Grid 1 Bias Voltage -6V
Anode Current Anode Current 36mA
Screen Current Screen Current
Output
Output Power Output Power (Class A SE) 4.5W
Heater
6 Metallization (external shield)
7 Suppressor Grid (internally connected to cathode)
TC Top Cap — Anode (top cap)
4mA
Anode Resistance Anode Resistance 50,000Ω
Transconductance Transconductance 9mA/V