C3M

C3M has no equivalent designation confirmed by the archive.

Description

The C3M is a special quality pentode designed for use as an A.F. and R.F. amplifier, output tube, oscillator, and similar applications. It has a loctal base and indirect heating, and can be operated on A.C. or D.C. with series or parallel supply.

Ratings

The heater is rated at 20 V and 125 mA; the average heater voltage should be 20 V, and variations outside the range of 19 V to 21 V will shorten tube life. Maximum ratings include an anode voltage of 300 V, an anode dissipation of 4 W, grid No. 2 voltage of 300 V with 1 W dissipation, grid No. 3 voltage of 300 V with 1 W dissipation, grid No. 1 voltage of 100 V with 50 mW dissipation, and a cathode current of 30 mA. When connected as a triode, the combined dissipation of anode, grid No. 2, and grid No. 3 is limited to 5 W. The maximum grid No. 1 resistor is 0.5 MΩ when anode dissipation exceeds 1.5 W, and 3 MΩ when anode dissipation is below 1.5 W. The maximum voltage between cathode and heater is 120 V, and the maximum bulb temperature for the metal envelope is 120 °C.

Characteristics

The C3M has an anode current of 16 mA, a mutual conductance of 6.5 mA/V, an amplification factor of 19 (grid No. 2 to grid No. 1), and an internal resistance of 250 kΩ. Its equivalent noise resistance is 1200 Ω, but is 650 Ω when connected as a triode and 5000 Ω for A.F. (500–3000 Hz). Hum voltage is 10 microvolts RMS. The cathode heating time is 26 seconds (range 19–33 seconds) at an anode current of 4 mA. The tube is rated for a life test of 10,000 hours.

Applications

As an output tube, the C3M delivers an output power of 1.5 W with an anode load resistance of 10 kΩ and total distortion of 10%.

Capacitances

Interelectrode capacitances include: grid No. 1 to grid No. 2, grid No. 3, cathode, heater and screen, 8.5 pF; anode to grid No. 2, grid No. 3, cathode, heater and screen, 6.0 pF; anode to grid No. 1, 14 pF; grid No. 1 to grid No. 2, 3 pF; grid No. 2 to grid No. 3, 2.2 pF; grid No. 1 to cathode and screen, 4.5 pF; anode to grid No. 3, 1.2 pF; grid No. 1 to heater, 20 pF; anode to heater, 120 pF; cathode and screen to heater, 7 pF. When connected as a triode (grid No. 2 and grid No. 3 connected to anode), the grid No. 1 to cathode, heater and screen capacitance is 5 pF; the anode, grid No. 2 and grid No. 3 to cathode, heater and screen capacitance is 7.5 pF; and the anode, grid No. 2 and grid No. 3 to grid No. 1 capacitance is 3.2 pF.

Datasheet

The datasheet for the C3M was published in December 1968.

Original manufacturer datasheets for C3M, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• S.Q. TUBE

1 further designation appears alongside C3M in the literature but below the evidence threshold used here, so it is not listed as equivalent.