> Hello.i am a SB220 owner.i just got it to work.clean it
> upp and all. after 4 years.but somthing is wrong i get 550
> W output?... and when i try the 3-500z each in single use
> i get 550w out on a single tube ?.and when i install then
> both i still get 550w..someone?
In grounded grid the gain does not change as much as we
expect when we parallel more and more tubes.
This is because in a grounded grid amplifier the output is
in series with the input and the impedance ratio mostly
determines the gain.
When you add tubes you have to increase drive to have
significantly more output.
You might have another problem, but don't expect to see
double power with double tubes. It won't happen in grounded
grid. When you install both tubes do they both appear to
show similar color on the anode when operating? What is your
power meter and drive power? What is the HV?
The SB220 was designed to run about 600W output on CW, and
1200W PEP on SSB output. It is a 1kW CW input, 2kW PEP SSB
output amplifier.
73 Tom
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