Marv, I have used this method in several grounded grid tetrode amplifiers
with excellent results. There is an added advantage that a big diode can be
placed from B- (cathode) and ground to snub any big voltages on the cathode
that
might happen during a plate to ground flashover event.
Not only will the diode protect the tube but also the grid and plate
metering circuits.
When you design the grid bias circuit, keep in mind that peak grid current
will be many times the indicated average current. I have used smallish zener
diodes connected to a potentiometer and emitter follower circuit with good
results in this application.
73,
Gerald K5GW
In a message dated 7/9/2008 11:45:14 A.M. Central Daylight Time,
wc6w_amps@yahoo.com writes:
Has anyone ever seen a design wherein an 8877, or similar triode, operated in
grounded grid has the bias generator placed in the grid return line, rather
than in the typical cathode (grid + cathode current) location?
This implies that the HV return must be allowed to float at least as
positive as the bias value. The grid remains chassis grounded as usual. And
the
advantage of this arrangement is that the bias generator need only pass the
grid
current which is typically 1/10 of the cathode current.
A proposed circuit may be seen at:
http://wc6w.50webs.com/wc6wamps/index.html?fr40.html
73 & Good morning,
Marv WC6W
http://wc6w.50webs.com/
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