Re: Sailor T128 Marine Transmitter.
At the risk of looking a bit like I am having an argument with myself here!!
I think I may have developed a theory - see attached diagram
there are diodes D603,D604 & D607 (highlighted orange) in the measuring circuit for S1002-position5.
I think the purpose of these diodes is to "block" the large negative grid bias from the meter, so that in the quiescent mode the meter will see 0V.
if one or more of these diodes has gone bad and shorty, the meter will see grid bias.
by extension, if this happens, there could be a low resistance path to 0V for the relevant grid(s), which case would presumably result in abnormally high anode current for the affected valves.
I am still seeing this *occasionally* on the middle valve (anode metal starts to get red hot) This only happens on keydown, which is I suppose because HT is only supplied to the caps on keydown.
please could more experienced eyes comment on the above leap of faith?
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