Edward Knobloch wrote:

What range of plate voltage/ grid voltage do you recommend,
and what current limiting resistor would you suggest
in the plate circuit?
Do you use a current limiting resistor in the grid circuit also?

Ed,

I use lots of airflow and a variable voltage grid supply. Since the
grid voltage is dc, you can use a simple Ig times Vg (to cathode) to
calculate dissipation. In a operating amplifier you would have to use a
Fourier (harmonic) analysis to calculate grid dissipation, but not at
dc.

Set the grid just below rated dissipation. When Eimac initially
gettered the tubes, they heated the grids well into color. I'm not that
bold, although they told me they could get almost white hot without
problems! So I stay at or below rated dissipation.

I use about 500-1000 volts of anode voltage, whatever it takes to show
good anode color. I use an old AL80B transformer for grid bias and HV,
except I don't voltage double the HV winding. A variac would be better,
I switch taps.

73 Tom

Why is the dissipation rating of the 4-400A lower when used in grounded grid
service than it is when used in the traditional configuration?

73,
Bob AD3K

"Bill Turner" wrote in message
...
ORIGINAL MESSAGE:

Straydog wrote:

there must be forced-air directed upwards from the non-tube side of
the tube socket and there are specifications for flow rate and
pressure.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Flow rate and pressure" are nice, but the *only* important thing is
the temperature of the tube at various points as specified by the tube
manufacturer. If you are serious about proper tube cooling, use either
a non-contact thermometer of some kind or thermally-sensitive paint to
ensure your tube is within temp specs. Flow rate and pressure are a
means to an end, not an end in themselves.

Bill, W6WRT