Identical electricals but 6.3 V parallel heater — not a drop-in in series-string heater circuits
Electrical Specifications
Absolute Maximum
Anode Voltage (max)Max Anode Voltage220V
Anode Dissipation (max)Max Anode Dissipation2.2W
Cathode Current (max)Max Cathode Current20mA
Heater-to-Cathode Voltage (max)Max Heater-Cathode Voltage100V
Max Grid Resistor
Notes
Series-heater (300 mA) version of the EC86. Electrically identical sections — only the heater voltage/current differs (3.8 V at 300 mA vs 6.3 V at 200 mA).
Designed for grounded-grid operation at UHF. Pins 2, 6, and 8 are all connected to the control grid, and pins 3 and 7 are both cathode — this multi-pin arrangement reduces lead inductance for VHF/UHF performance.
The 4CM4 is the American RETMA designation for the PC86.
Max heater-to-cathode voltage is asymmetric: 100 V (cathode positive) vs 50 V (cathode negative). Max Rkf = 20 kOhm.
Equivalent noise resistance (Req) is 230 Ohm — unusually low, reflecting the tube's design for low-noise UHF front-end service.
Pin Layout — Noval
1Anode
2Control Grid
3Cathode
Socket-Compatible Tubes ⚠ Not electrically compatible