plate detector bypass cap - Printable Version

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+--- Thread: plate detector bypass cap (/showthread.php?tid=8288)

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plate detector bypass cap - morzh - 12-30-2013

Well, I was suspicious of that correction we made to the sch of 90 making the caps in that Plate detector circuit 35pF - I thought it was not sufficient so I kept the cap thwt was there which is 350pF and the other cap after the choke I also made 350pF, as it was originally in the schematic.

Now, when it comes to the first cap it is the plate bypass cap and it is recommended in Plate Detectors to be chosen like follows below:

(From Wikipedia)

>>>>A plate bypass capacitor (usually 500 pF to 0.002 µF for triodes, or 250 pF to 0.001 µF for tetrodes and pentodes) is used to regulate plate current.<<<

So it makes sense that it was shown 350pF and not 35pF (we have a tetrode). After all the criterion is the impedance of the cap should be small enough for RF while large for audio.

Another source also lists it about 250pF. And the similar values are in the 70 sch, that one which also uses plate detector.

So even though we have a radio which does have 35pF there, maybe there is a good reason there should be 350pF.

I wonder if more people have a 90 with plate detector (especially that with 2x45 output). So we could have more data.

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