E83F

The E83F, also designated 6089 in Philips' sheet, is a Special Quality pentode designed for telephone equipment. The documentation highlights long life and low cathode interface resistance. Heating is indirect, at 6.3 V and 300 mA, on AC or DC, with series or parallel supply. Its Noval base has gold-plated pins, a construction detail expressly stated by the manufacturer.

At Philips' nominal point, with 210 V plate, 120 V screen, zero suppressor voltage and a 165 Ω cathode resistor, plate current is 10 mA, screen current 2.1 mA, transconductance 9 mA/V and internal resistance 0.5 MΩ. The 10,000-hour life expectancy is tied to these conditions and the permitted characteristic ranges during useful life; it does not mean all values remain identical to their initial values. Earlier sheets also prescribe heating variations below ±5% in voltage for parallel connection and ±1.5% in current for series connection to obtain that life.

Philips also documents class A audio output operation. With the screen supplied from 120 V through 5.6 kΩ, a 180 Ω cathode resistor and zero suppressor voltage, the 120 and 210 V plate points use 10 and 20 kΩ loads respectively. With 1.1 V RMS input they deliver 340 and 660 mW, both at 10% total distortion. The same table lists 400 and 870 mW when positive grid current reaches 0.3 µA with a 0.33 MΩ grid resistor; these have different conditions and their columns do not specify that same 10% distortion. Thus 870 mW should not be quoted as unqualified audio output.

Philips' design-centre limits include 210 V plate and screen, 2.1 W plate dissipation, 0.35 W screen dissipation and 16 mA cathode current. The 550 V stated for plate and screen with a cold cathode is not the normal operating voltage limit. The 80 mA peak cathode current is also conditional on pulses no longer than 200 µs and a maximum duty factor of 0.1. The heater-to-cathode limit is 100 V; with automatic bias the grid resistor must not exceed 1 MΩ.

In Philips' pinout, screen, control grid, cathode and plate are on pins 1, 2, 3 and 6 respectively; the heater is between 4 and 5, while 9 combines suppressor and shield. Pins 7 and 8 are internal connections and must be recognised as such. A maximum plate-to-control-grid capacitance of just 0.015 pF completes the 1968 sheet's electrical picture. Special Quality therefore describes documented characteristics and conditions that should be retained when comparing this tube with other pentodes.