When a service oscillator is available, the AVC action of the receiver should be checked since sometimes the trouble in a receiver can be caused by a failure in that circuit. With the generator connected to the antenna and ground terminals of the receiver, the Electronic Voltmeter should be connected to each grid in turn in the RF or IF sections of the receiver and the AVC voltage measured at each grid at various input-signal levels. Since there is no hard and fast rule that can be set down concerning the number of tubes controlled in a receiver, or the percent of available AVC voltage applied to each tube, the only general statements that can be made are the following:

1. In a receiver with one IF stage it is the usual practice to apply full AVC voltage to the IF, Mixer and RF tube (if any). Sets having composite oscillators usually have no AVC on the Mixer (composite oscillator).

2. In receivers with two IF stages it is frequently the practice to apply only a portion of the available AVC voltage to the second IF tube. This portion is usually one-half or one-third. In some receivers of this type no AVC voltage is applied to the last IF tube.

3. In high-frequency receivers, or on the higher frequency bands of multi-wave receivers the AVC voltage is frequently removed from the Mixer circuit.

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