[Amps] SB200 on 6m & my take

[Carl]

I'll be briefer. Since when isnt the 572B rated to 6M?

Carl
KM1H


----- Original Message ----- 
From: "David Craig" <davidhcraig at verizon.net>
To: <amps at 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
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