3A4

3A4 is also designated DL93.

The 3A4 is a power pentode with a directly heated cathode, intended for output amplifier and oscillator service in battery-operated equipment.

Construction

The 3A4 uses a miniature 7-pin base designated 7C10. It can be mounted in any position. The filament is split into two sections. For parallel filament supply, the filament voltage is 1.4 V at 200 mA; for series supply, the voltage is 2.8 V at 100 mA. In series operation at 1.35 V, the two filament sections are connected in parallel, and in series operation at 2.7 V they are connected in series. Pin 1 is the negative filament pole for series operation, pin 5 is the negative filament pole for parallel operation and also serves as the filament center tap and internal shield (grid 3), and pin 7 is the positive filament connection. Pins 2 and 6 are the anode connections, pin 3 is the screen grid (grid 2), and pin 4 is the control grid (grid 1).

Ratings

The maximum anode voltage is 150 V, and the maximum anode dissipation is 2 W. For AF output amplifier service, the maximum screen grid voltage is 90 V, the maximum screen grid dissipation is 0.4 W, and the maximum cathode current is 18 mA. For RF output amplifier service in intermittent operation at 50 Mc/s, the maximum screen grid voltage is 135 V, the maximum screen grid dissipation is 0.9 W, the maximum grid 1 voltage is 30 V, the maximum cathode current is 25 mA, and the maximum grid 1 current is 0.25 mA. The maximum operating altitude without pressurization is 3 km.

Characteristics

In class A AF operation at an anode voltage of 135 V and screen grid voltage of 90 V, the transconductance is 1.9 mA/V and the internal resistance is 90 kΩ. At an anode voltage of 150 V and screen grid voltage of 90 V, the internal resistance is 100 kΩ. The grid 1 to anode capacitance is 0.35 pF maximum, the input capacitance is 4.8 pF, and the output capacitance is 4.2 pF.

Applications

The 3A4 is intended for use as an oscillator or amplifier, including class A AF output amplifier service and RF output amplifier service in intermittent operation. The directly heated cathode can operate from battery current, rectified AC, or DC, and the tube can be used with series or parallel filament supply. The Miniwatt literature designates this tube as DL93; the Miniwatt datasheet for the DL93 (3A4) dates from 11.11.1949.

Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.

Original manufacturer datasheets for 3A4, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• DL93 *"Miniwatt"* (filed under DL93)
• PENTODE DE PUISSANCE