----- Original Message -----
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
To: <amps@contesting.com>
Sent: Friday, July 30, 2010 12:41 PM
Subject: Re: [Amps] More parasitic choke questions
> ORIGINAL MESSAGE:
>
> On Fri, 30 Jul 2010 07:24:29 -0400, "Carl" <km1h@jeremy.mv.com> wrote:
>
>>I guess that means that you are unable or incapable of backing up your
>>statement. Here it is again for you.
>>
>>"If that were true, why do we see so many burned up suppressor
>>resistors in both homebrew and commercial amps?"
>>
>>I'll ask again... what commercial amps are burning up suppressors??
>
> REPLY:
>
> Of my personally owned commercial amps, the Command HF-2500 had burned
> parasitic suppressor resistors. Just in the last three days, the
> following posts have expressed the same problem:
>
> Posted by Martin Sole July 27, 2010:
>
> "The aging resistors are going high though so increasing the Q which
> may not be ideal. Looking at 3 amps, a 30L-1, a Henry 2K Classic X and
> an Alpha 78 all of them show an increase of R above the spec of the
> old carbon resistors original value. In the case of the Henry the
> increase is about 100%!"
>
> Posted by Jim Barber July 29, 2010:
>
> "For example, my Henry 3KA (2x 3-500Z) needs occasional
> attention to the suppressors to keep it from oscillating."
>
> So to answer your question, Carl, that's Collins, Henry, Alpha and
> Command. And that's just in the last three days. Go back in the
> archives several years and you will find many more examples.
>
> And I'll make a prediction: In the next few years as sunspots
> increase (hopefully) and ten meters becomes more heavily used, the
> number of burned suppressor resistors will increase greatly.
>
> Does that answer your question?
>
> 73, Bill W6WRT
I see then that you blame vintage 30-50 year old amps with cooked
suppressors as proof of poor design. Or in the case of the HF-2500 about 15
years old and most likely tuned by someone not familiar with the procedure
as the 3CX800A7 is one of the hardest tubes to get to take off. The HF-2500
Ive recently rebuilt has seen heavy contest duty and the suppressors are
fine as are the original tubes.
Perhaps you simply ignore the history of carbon resistors that go way up in
tolerance simply by sitting around. Im pretty sure that amp manufacturers
werent splurging for the more expensive and high quality Allen Bradley
version.
I predict that suppressor resistors will continue to fry as long as carbon
composition are used. Contesters use 10M at any part of the cycle even to
get just a few points, and there is a full blown 10M contest every year; I
rarely hear of them having problems.
Bill I really feel sorry for you when you show your incompetance in such a
grand manner. I suggest again that you actually read and understand the
purpose of a suppressor.
Carl
KM1H
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