ORIGINAL MESSAGE:


I don't remember where I have read that only the control grid had
physically push to ground, while the others grid(s) was electrically
floating and connected to ground through of the capacitors....


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The control grid should be connected directly to ground but never allow
the other grids to float. They must either be connected to a standard
bias supply or grounded themselves. If they are floating, they will
pick up a charge and do things you don't want them to do. :-)

Connecting all grids to ground was a common practice in the old days
but is rarely done anymore, due I believe to bad linearity. If you're
only doing CW, FM or RTTY, linearity is not an issue and it should work
fine that way.

Bill, W6WRT