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Old 15th Nov 2017, 11:15 pm   #2
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: Ferguson 901-AC.

Why would someone miss a leaking capacitor? If they knew enough about electronics to realise that the anode current was excessive, and that increasing the cathode resistor would reduce it, surely they would have known that the grid would have to be negative with respect to the cathode.

They must have taken some DC voltage measurements in order to know that the output stage current was excessive, so how could they not suspect the DC blocking capacitor? If somebody just tried diving in, with no circuit diagram and no measurements, what are the odds against them picking the output valve cathode bias components and effecting a sort-of cure? (Assuming nothing else was disturbed.)

The mind really does boggle sometimes .....
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