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>Need a little help finding some Cetron 572B tubes for my Yaesu FL2100B
>amp (yes, I'm just a little pistol, but 500-700 watts works fine for me
>execpt when trying to work BS7H). At least one of the finals has gone
>south and max output is now limited to about 350 watts.
What failed in the tube that went south to kaputsville, Tom?
> It used to hit
>700+ when the finals were new after Yaesu replaced them and did some
>other work on it. I know Svetlana makes a 572B that is supposed to be
>fairly heavy duty, or so I've been told, but major circuit modifications
>are necessary to use that tube, so the Svetlana people tell me.
Svetlana 572B and 811A tubes apparently exhibit more VHF gain than other
manufacturers' tubes. This is good news if one is trying to build a VHF
oscillator, but hardly good news in amplifier service. You could lower
the VHF gain in your FL-2100B by using a VHF parasitic suppressor with a
lower VHF parallel equivalent resistance (Rp). . An Rp suppressor
comparison can be found at:
http://www.vcnet.com/measures
see Figure 12.
>Anyone
>have a source for Cetron? I understand they are more expensive than the
>Svetlana or similar Chinese brand. Any help appreciated.
(Eddie) Richardson Electronics Ltd. in Chicago used to sell Cetron tubes.
However, the use of new Cetron tubes is no guarantee of unconditional
VHF stability. Although rare, I have heard reports of a 'big-bang' and
the filaments suddenly breaking when new Cetron tubes were installed.
Even though one "expert" blames filament breakage on mechanical defect,
it seems a bit unlikely to me that two 572Bs would experience
simultaneously broken filaments unless both 572Bs were dropped from about
5 feet onto a firm carpet.
>Tom, WW5L
Rich---
R. L. Measures, 805-386-3734, AG6K
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