I'll be briefer. Since when isnt the 572B rated to 6M?
Carl
KM1H
----- Original Message -----
From: "David Craig" <davidhcraig@verizon.net>
To: <amps@contesting.com>
Sent: Friday, March 13, 2009 12:44 AM
Subject: [Amps] SB200 on 6m & my take
> Brief & to the point- they stink, monoband or (worse) tapped
> bandswitch "models". They may be fine for the occassional SSB QSO
> without pushing it, but otherwise they do one thing with regularity-
> they die/burn out/self-destruct. RTTY? WSJT & other digicrap with
> 100% duty cycle for 30-55 seconds key-down? Result? Be ready for a
> buzz, hiss, POP & Boom & to buy a new amp, or parts that cost enough $
> to build a new one. I don't do any digital myself save cw but if you
> want a list of dead SB200 conversions (owned by others) I'll be happy
> to provide them, some were EME deaths & others that just "crapped out"
> due to tubes that aren't ment to be used at that QRG.
> I don't care what you can "get away with", I want something that
> isn't going to crap out because the tubes aren't rated for 50MHz use.
> SB200s should be left to HF. If you are still going to convert one,
> do what I am doing and put a 3CPX800 in it with new cooling and a new
> FWB PS and appropriate transformer. Otherwise build one with an
> appropriate tube/s from scratch which I have also done x 3. 572Bs are
> a lousy tube for 6m conversion unless your habit is to run it a few
> hours per year.
> Oh, one last thing- for parasitic suppressors, don't be lazy and
> use the resistor leads as a soldering surface for the L (really a "U")
> between resistor sides on a 6m conversion. I have seen 4 cases so far
> of that method resulting in heat melting the "L" on the plate-block
> side... ergo all B+ plus RF current passes thru the resistors &
> softens the tubes in seconds. $600+ $ down the tubes.
>
> N3DB
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|