[Yaesu] re 572B's in FL-2100

Tue, 15 Jan 2002 18:20:58 -0500

I ordered two Svetlana 572Bs last spring for my SB-200 from RF Parts.
After only one month one of them blew its filament.  RF Parts
replaced it and at the same time I ordered a pair of Taylor tubes
which I now have in the amp.  So far, so good.

When speaking with RF parts about this they said at the time they
were no longer going to carry Svetlana tubes because of problems
getting shipments.  However, Svetlana has since appointed a new US
distributor so that may no longer be a problem.

I also have read that using Svetlana 572Bs in the Yaesu amp may lead
to oscillation because of the slightly higher stage gain of the tubes
and the lower cutoff bias as compared to the SB 200.  Others have
mentioned a mod kit which I understand does work and should be used
if you do decide on the Svetlana tubes.

While the Taylor tubes seem to be working well (at least the
filaments haven't popped) I do seem to be getting slightly lower
output than I would have expected - - 400 to 600 watts, depending on
the band, as measured by my Coaxial Dynamics peak reading watt meter.
The plate voltage is nominal.  However, I do run it on 120 Volts as
compared to my "big amp" which is on 240 volts with a pair of 3 CX
800A tubes.  But the difference between what I'm getting and the
perhaps 700-750 watts I would have expected is not enough to get
exercised about I think.

Bruce - W8FU
----- Original Message -----
From: "Fern Rivard" <[email protected]>
To: <[email protected]>
Sent: Monday, January 14, 2002 7:50 PM
Subject: [Yaesu] re 572B's in FL-2100

>     Could some please enlighten me as to the best tubes to use as
> replacements in Yaesu FL-2100B amplifier.  I see that RF Parts
carries at
> least three different brands. It looks like the Taylor replacements
are the
> best buy but there is a warning that using the Svetlana brand would
require
> a modification to the FL-2100 amp. What is this mod that they are
talking
> about?
>     Another supplier only carries the National brand which I have
never
> heard of before but they are made in China. My guess is that those
tubes
> can't be used in the horizontal position.
>     Any comments or suggestions would be greatfully appreciated.
73's from
> Fern
>
>
> _______________________________________________
> Yaesu mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/yaesu
>