I am considering buying a quad of 572B tubes and want your
some recommendation. Please help me with my buying decision.
I have 2 Dentron Clipperton L amplifiers. One has a set of 4 old
(unmatched) Cetrons and the other a set of 4 relatively new Star
Chinese tubes (I just bought the amplifier with Star tubes from a
known source). All tubes described here performed equally well in
either amplifier.
The quad of Cetrons produce the expected 1250 watts (80m & 40m) with
an input impedance that matched the solid state transceiver of 100
watts with no intermediate tuner required.
The Chinese Star tubes require the automatic tuner in the transceiver
to get above 200 watts output. Even with the transceiver tuner in
line, they put out only about 700 watts. The Chinese tubes clearly
are inferior. At least, this set has a problem.
In the past, I have owned Heath SB200 amplifiers, also with Cetron
572B tubes, and can attest to the consistent performance of those
tubes from one to another.
I can buy 4 Cetrons that are a known quantity. They cost more, and I
don't really know who sells these any longer?
I can save some dollars buying the Svetlanas. But to me, the Svetlana
tubes may be just as risky as the Chinese tubes.
Please answer a few questions for me.
o I can buy more Star tubes and take a chance, but experience says
that is what I would be doing. Please comment based on your
experience?
o Should I buy Svetlana tubes that RF Parts promotes?
o Why should I feel comfortable that they have the same consistent
quality as the Cetrons?
o Do you know of any reason Svetlanas would not work well in the
Clipperton L?
o Should I expect the Svetlanas to be as good as the Cetrons?
o Anyone else using the Chinese Star tubes, but do you have any
experience that will help me understand them?
o What about this talk about a matched pair? Is it worth the extra
$$$$????
Supposedly a matched quad, the Chinese 572B tubes were marked with
handwritten figures of 103, 125, 126, and 131. By itself, the one
marked 103 produced 30 watts out for 100 watts in and clearly has a
serious problem. The other three each produced 200 watts when
tested one at a time in the same socket. All the Chinese tubes,
either together as a quad, or one at a time, required the
transceiver antenna tuner to be used.
The old Cetrons in the same one-at-a time test situation offered 250
watts, 250 watts (requiring the tuner), 350 watts and 350 watts.
Why would 2 year old Star tubes have such a bad input impedance as
to require an antenna tuner between them and the transceiver?
o Besides the lower output and the requirement for the tuner, is there
any problem running the Clipperton L with the 3 Star 572Bs that have
reasonable output?
Thank you in advance for your assistance as you guide me in my
probable purchase of 572B tubes. Thanks Scott KQ8RP
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