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Here the signal should reach its
highest level. A gain of 10 to 20 is
normal for pentodes and 2 to 5 for
triodes.
The a.c. plate current creates a strong field around (glass) tubes and the plate wiring, including the output transformer. Thus, the signal may be heard when the probe is merely brought near to these parts. Trouble In this part of the circuit, trouble is easily located. The components are simple and the input signal is at a high level. No signal at R may indicate a defective tube, wrong voltages, open output transformer primary, break in wiring, or failure of some other component. Voltage and continuity tests give the answer quickly. |
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