I think what Rich is saying is that when the suppressor is found to be bad by
either an open or out of tolerance resistor, it may be better to change the
whole thing using the resistance wire as the old original article suggests that
he referred too years ago. Just changing the resistor certainly can cure the
problem, but the kit could actually be better than the original design by
dropping the Q more than it was in the original suppressor design using copper
wire. I've used suppressors with copper coils for all new amps I've ever built
because that's what everyone else did. I've personally seen squirelly amps that
suppressors cured. I have also seen two amps of the same model act totally
different, one being squirelly and one not with no noticeable changes between
the two. As a matter of fact, I've seen some run fine without the suppressors,
but another of the same model need them. In Heathkit especially they can change
from amp to amp because different folks built them and
I have seen layout changes between each one.
The one supposed test I seen on the net which was very flawed, was meant solely
to discredit the suppressors. If I were to have ran the test, I would have ran
it on knowingly squirelly amps (ones folks said went into oscillations, etc)
instead of ones that were operating, and never showed a sign of doing it. It's
easy to take 2-3 good acting amps and run a test to dis-prove parasitic
oscillations. Evidently, the one doing the test never done enough service work
in his life, nor actually hands-on built enough amps to have actually seen this
phenomenon. One can set at a drawing board or computer all day long designing
amps, quoting theory, and never have actually done the work enough to see the
problems. I've seen this time and time again in engineering offices. A good
engineer will take the input from the assembly floor, QC, service shop, and
especially customers to heart, not dismiss it.
Best,
Will
*********** REPLY SEPARATOR ***********
On 6/1/06 at 8:18 PM k7fm wrote:
>"I have had dozens of Sb-220 amps in my almost 40 years as a ham. Most
>of
>the parasitic suppressors I have changed had their carbon resistors change
>value enough to make them not as effective as suppressors should be. Most
>of the
>time a change of resistors will tame a quirky Sb-220."
>
>Let us follow this statement with basic logic.
>
>1. The SB-220 becomes unstable when the carbon resistor changes value.
>2. When that happens, ham A changes out the parasitic suppressor by
>installing Rich's nichrome suppressor kit, which just happens to include
>an
>excellent and stable replacement resistor for the aged carbon resistor.
>3. Ham A installs the kit, complete with the new and stable replacement
>resistor.
>4. The SB-220 is stable again.
>5. Grateful ham A exclaims to the world that it is Rich's marvelous
>suppressor fixed the problem.
>
>It seems the poor resistor has been neglected and is not receiving the
>credit it deserves.
>
>I am not trying to discredit Rich's research or opinions. I just want to
>give a little more credit to the resistor. It seems under appreciated in
>this whole affair.
>
>Colin K7FM
>
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