If the tubes are not actively driven into cut off (no gain) the amplifier, even though it is neutralized, will possibly oscillate even though it is neutralized. In the standby mode, neither the input nor the output of the amplifier are terminated, and the plate supply voltage is ON. It is not surprising, since if the tubes exhibit sufficient gain, and there are no resistive terminations on either the input or the output, oscillation may occur, even in a well designed amp. Otherwise, the plate and load or band settings would be irrelevant. This is the classic definition of instability. W8JI states that in some cases the clicking happens on different bands with varying plate and loading settings. It automatically extinguishes when the arc suppressors fire, upsetting the bias. The burst of oscillation is very brief, and no current is indicated on the plate meter. The only purpose I could see it serving was to terminate the input circuit by resistive loading, to reduce a tendency to break into a burst of RF oscillation due to the tubes not being properly biased OFF. The 200 ohm resistor does not have a DC path to the cathode circuit, so I did not understand how it would improve the cut off bias situation. I put it in, after we encountered a clicking noise in the receiver in amplifier standby mode. Installation of the 200 ohm swamping resistor is 'optional', according to the W8JI instructions.
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