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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