Installation And Application

The base pins of the 802 fit the 7-contact (0.8T5-inch pin-circle diameter) socket which may be mounted to hold the tube in any position.

When the heater is operated from a d-c source, the cathode circuit is tied to the negative heater supply lead. In circuits where the cathode is not directly connected to the heater, the potential difference between them should not exceed 100 volts.

The internal shield should be tied to a terminal operating at zero r-f and/or a-f potential. In most cases, this connection will be made to the cathode or suppressor terminal.

Adequate shielding and isolation of the input circuit and the output circuit are necessary if optimum results are to be obtained. If an external shield is employed with the 802, it should be designed to enclose the base end of the • '-f and extend up to a point level with the bottom of the internal shield.

Clearance between the glass bulb and external shield should be at least -fa". The impedance between the screen and cathode must be kept as low as possible by the use of a by-pass condenser.

The plate of the 802 shows no color at the maximum plate-dissipation rating for each class of service. The screen should not be allowed to show more than a barely perceptible red color.

As a pentode or tetrode oscillator (crystal or self-excited), the 802 may be operated under the conditions shown for class C telegraph services. Because the internal shielding in this tube is unusually effective, it generally is necessary to introduce externa] feed-back in those circuits which depend on the control-grid-to-plate capacity for oscillation. This may be done by the use of a small condenser not larger than 2 to 3 mil connected between control grid and plate.

For high-frequency operation above 30 megacycles, see page 144.

For additional information, see chapters on INSTALLATION and APPLICATION.

average plate characteristics

Cf:t.) VOLTS

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