Do you have a copy of that Heath Service Bulletin ? Or know if
it is on-line ?
73, Dick, W1KSZ
> From: km1h@jeremy.mv.com
> To: w1ksz@q.com; amps@contesting.com
> Subject: Re: [Amps] [Heathkit] The SB-220
> Date: Sun, 23 Aug 2009 10:24:08 -0400
>
> Amen to that.
>
> The huge majority of amps that I buy for 6M conversion are 100% untouched by
> voodo science and have no signs of problems ever.
>
> OTOH, a few with directly grounded grids Ive bought real cheap since a tube,
> meter, bandswitch, zener, or all the above is blown.
>
> I can guarantee that any SB-220 that is acting up can trace the problem to
> out of tolerance suppressors, dirt, nicotine. Voodo kits will work and so
> will new resistors, its a matter of choice as neither offers more than the
> other.
>
> Keeping the grids above ground enough to reduce tube gain a bit is still the
> best way for long term stability with any brand and combination of tubes.
>
> I realize that most on here dont own a spectrum analyzer and many dont have
> a clue about neutralization. While the SB-220 is pretty stable as designed
> it can take off under some tuning conditions, tuners, antennas, etc. No
> amount of nichrome will help. Reducing gain will. Or adding a neutralizing
> circuit which isnt worth the effort.
>
> If some want to create a cottage industry by offering unneeded modifications
> to the unknowing then go for it. Its the American way and P.T. Barnum would
> be proud.
>
> Thats simply not my ethic.
>
> Heath had a service bulletin to keep the filament transformer from burning
> out when a fault occurs. This affects 240V operation only and is a simple
> rewiring at the switch. Later kits had the change.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "RICHARD SOLOMON" <w1ksz@q.com>
> To: "Amplifier Reflector" <amps@contesting.com>
> Sent: Saturday, August 22, 2009 9:09 PM
> Subject: Re: [Amps] [Heathkit] The SB-220
>
>
> >
> > I must lead a charmed life ... in 54 years of Hamming and three
> >
> > SB-220's along the way, I have never had such catastrophic
> >
> > failures as I have seen described. In fact, several of my friends
> >
> > who also had SB-220's have experienced similar luck. And we
> >
> > were not known for treating these amps with kid gloves.
> >
> >
> >
> > There must be some random failure mechanism that has not
> >
> > migrated to One land ... perhaps the cold ??
> >
> >
> >
> > That being said, insurance is always a good thing and I have
> >
> > already installed the AG6K suppressors in my 6 Meter Conversion
> >
> > and the bias mod will be next. Can't be too careful you know !!
> >
> >
> >
> > 73, Dick, W1KSZ
> >
> >> Date: Sun, 23 Aug 2009 08:59:34 +0800
> >> To: amps@contesting.com
> >> From: vk6apk@bigpond.com
> >> Subject: Re: [Amps] [Heathkit] The SB-220
> >>
> >> Good on you Lon. Well said.
> >>
> >> My experiences are similar to your's. In every amplifier that I have
> >> installed Nichrome, whether commercially made or home brew, the
> >> change has been very noticeable.
> >>
> >> I don't care who invented the idea or how it works. I don't care
> >> about others who say it doesn't work and that it is snake oil. I just
> >> know that I'll continue to use it and enthusiastically recommend it to
> >> others.
> >>
> >> Whether it cures the cause or the symptoms, is totally irrelevant to
> >> me. The science and the maths are of no concern either.
> >>
> >> I compare it to silicon sealer, self drilling screws, battery drills
> >> and the like. Life would be dreadful without them.
> >>
> >> 73, Alek
> >> VK6APK
> >>
> >>
> >>
> >>
> >> At 03:13 AM 23/08/2009, k5jv wrote:
> >> >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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> >> >
> >> >
> >> >
> >> >
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