EF806S

EF806S has no equivalent designation confirmed by the archive.

Description

The EF806S is a low-frequency pentode of special quality, intended primarily for the input circuits of low-frequency amplifiers where low microphony and little hum are required. It is an all-glass miniature tube with a nine-pin base, using indirect heating with an oxide cathode for parallel supply with alternating or direct current. The suppressor grid and internal shielding are brought out to separate pins on the base.

Construction and Ratings

The EF806S uses base S 9/12 per ČSN 35 8904 and has a maximum weight of 16 g. Its heater requires 6.3 V ± 5% at 0.2 A, with a maximum heater voltage of 6.6 V. Maximum ratings include an operating anode voltage of 300 V, a cold anode voltage of 550 V, and an anode dissipation of 1 W. The screen grid is rated for a maximum operating voltage of 200 V, a maximum cold voltage of 550 V, and a maximum dissipation of 0.2 W. Maximum cathode current is 6 mA. Maximum control-grid leakage resistance is 10 MΩ when anode dissipation is below 0.2 W, and 3 MΩ when above 0.2 W; maximum control-grid resistance for bias by grid current is 22 MΩ. The maximum voltage between cathode and heater is ±100 V, with a maximum external resistance between cathode and heater of 20 kΩ. Maximum bulb temperature is 170 °C. The maximum bias for onset of positive grid current (Ig1=+0.3 μA) is 1.3 V.

Electrical Characteristics

Under stated conditions, the EF806S has an anode current Ia of 3.2 +0.6/-0.5 mA, a screen-grid current Ig2 of 0.6 ± 0.15 mA, a transconductance S of 2 ± 0.4 mA/V, a screen-grid amplification factor μg2/g1 of 38 ± 10, and an internal resistance Ri of 2.5 +1 MΩ. Control-grid negative current -Ig1 is less than -0.1 μA. Cutoff anode current (Ug1=-6 V) is less than 150 μA. Insulation current of the heater (Uf=6.3 V, Uk/f=100 V) is less than 15 μA, and insulation current between electrodes (Uf=6.3 V, Ust=250 V, R0=10 MΩ) is less than 3 μA.

Special Quality and Noise Performance

The EF806S meets requirements for special-quality tubes including long-term vibration for 100 hours at 2.5 g acceleration at 50 c/s, individual shocks with 500 g acceleration lasting about 1 ms, repeated shocks 2×5000 at 10 g acceleration, constant centrifugal acceleration of 10 g, narrow tolerances, reliability of operation, and guaranteed long life (calculated as a mean value for 100 tubes). In the frequency band 25–10000 c/s at supply voltage Ub=250 V and anode load resistance Ra=100 kΩ, the equivalent noise voltage at the control grid is less than 8 μV (average 2 μV). Under conditions U0=250 V, Rg2=400 kΩ, Ck min=100 μF, Rk=1000 Ω, Rg1=0.3 MΩ, the hum voltage must not exceed 8 μV. With regard to microphony, the EF806S can be used in working conditions where the effective drive voltage is at least 0.5 mV for an output power of 50 mW, and the mean acceleration must not exceed 0.015 g at frequencies greater than 500 c/s or 0.06 g at frequencies less than 500 c/s, measured at a loudspeaker power of 50 mW.

Capacitances

The EF806S has an input capacitance of 4 ± 0.8 pF, an output capacitance of 5.5 ± 1.1 pF, a transfer capacitance of less than 0.05 pF, and a capacitance of control grid to heater of less than 0.0025 pF.

Original manufacturer datasheets for EF806S, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• **EF806S**