[Amps] SB200 on 6m & my take

[David Craig]

    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