If you run 500W PEP only, your tubes will quickly become gassy.
They have no separate getters. The gettering is done by the anodes
and so they must become red during operation to keep them healthy.
This happens in Australia as well where we have 400W PEP limit.
At that level, the anodes never get red, so the tubes fail very
quickly.
You will need to exercise your amplifier at full power regularly
to ensure healthy tubes.
73, Alek VK6APK
On 8/01/2025 2:16 pm, Fran?ois via
groups.io wrote:
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Thank
you for your patience
?
As
for the resistors at the terminals of the filter capacitors,
I understood that they allowed to distribute the voltage at
the terminal of each capacitor fairly. It is like for the
rectifier diodes with respect to the reverse voltage. This
point is understood.
?
Indeed
the quiescent current of the 3-500Z tubes is probably
sufficient without requiring the bleeders. You confirm to me
that the no-load voltage (in Rx) will not exceed 2650 V, or
330 V per capacitor.
?
Ok
for the 50 k? resistor in the grounding of the cathodes. It
is the equivalent of what was called automatic polarization
and it is indeed stabilizing. It is probably preferable to
constitute it by two resistors in parallel in case one cuts
out. You suggest that in Tx, the cathode circuit (the CT of
the xfmr wire as you say) is made as you indicate to me:
?
Note,
Drake did not use any bias at all on TX....and idle
current was very high ( 210-230 ma). Wire 10 x 1N5408
diodes in series....... in series with the CT of the xfmr
wire. The 10 x diodes will provide for 7.2 vdc of bias.
This will reduce the idle current down to 100 ma.
?
·????????
Do
you think that we could use a zener to replace the string of
diodes?
·????????
Have
you noticed the appearance of linearity distortion by
reducing this quiescent current?
?
Be
aware that in France, our HF power is legally limited to 500
W PEP. The two 3-500Z will therefore generally operate at a
slow trot
--
F1AMM
Fran?ois
De
la part de
Jim VE7RF via groups.io
贰苍惫辞测é?: mardi 7 janvier 2025 22:35
