Any material be it nichrome,stainless steel,or any other poor conductive
metal will de-tune the anodes and resist the tendency for parasitic
occillation.It also lowers efficiency on the higher frequencys and the added
resistance tends to change value when subjected to extreme heat.Why not use
conventional suppressors at the cathode(s)? I did such many years ago to
tame a pair of 4-1000`s..Worked FB..Did I miss a post here where someone was
poking at Mr Measures? QRZ??? Jim..K7RDX..
----- Original Message -----
From: "k5jv" <k5jv@kingwoodcable.com>
To: "Amp Reflector" <amps@contesting.com>; "heathkit reflector"
<heathkit@mailman.qth.net>
Sent: Saturday, August 22, 2009 12:13 PM
Subject: [Amps] [Heathkit] The SB-220
> Greetings to all,
>
> I usually do not comment on topics like this but could not resist
> this time. I, also, have been repairing amps for about 40 years -- have
> probably worked on 100 SB-220's. I think it is the best watt/dollar
> available in an amplifier today. However, as it was originally designed,
> it
> is just an accident looking for a place to happen.
>
> I use nichrome wire (nichrome ribbon in larger amps) in the anode
> suppressors, not because it is the best material, but because, as Richard
> Measures said nearly thirty years ago, it is relatively easy to work with,
> readily available, inexpensive, and does the job. In all my years in
> working on amps, I have never had, even one, come back for service, of
> parasitic related problems, after installing Measures parasitic
> suppressors.
> I personally think that input network changes are as helpful, or more,
> than
> the anode changes.
>
> After parasitic suppression, I think the most important
> modification
> is the bias mod. I do not know how many filament transformers I have
> replaced in SB-220's over the years, but it is safe to say that not one of
> them would have needed replacement if the bias mod had been done. If you
> want to really make a nice amp out of your SB-220, you might want to
> consider Richard's QSK mod. It is relatively cheap, not too difficult to
> install, and really works.
>
> Another great amp is the Kenwood TL-922. Of course, it is nothing
> but a cleaned up SB-220, but, it is even more parasitic prone, due to
> placement of components in the final compartment, than the SB-220. It,
> also, needs the bias mod and a soft start mod. QSK makes this amp a
> pleasure to operate.
>
> I have known Richard Measures for nearly forty years. He is one of
> the real thinkers in the Amateur Radio field. I do not agree with
> everything he says, but I have never, not even once, found him to be wrong
> wrong. No one else has either. Remember, they almost burned Galileo at
> the
> stake for saying that the world is round.
>
> 73 de Lon, K5JV
>
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> http://lists.contesting.com/mailman/listinfo/amps
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