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Author Topic: tl922 amp parasitic suppressors  (Read 17722 times)
K1ZJH
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Posts: 3300




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« Reply #15 on: May 27, 2012, 12:16:23 PM »

I don't believe W8Ji ever proposed a "universal" replace parasitic suppressor for the
3-500Z or any other tube. From what I've read on his website he develops the
correct parasitic suppressor for a particular amplifier design/layout and verifies the
value by carefully testing the amp at various load and tune configurations to ensure
that the amp is unconditionally stable.

What was wrong with the original suppressor?  There are several mods that can be
done to the TL-922, including improving the RF chassis circulating currents by
improving the ground on the tuning cap, and by adding a glitch resistor to limit
damage in case of an arc over.

Pete
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K4RVN
Member

Posts: 30




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« Reply #16 on: May 27, 2012, 02:20:16 PM »

Hi Pete,
Tom did a rework of the Kenwood 922 for parasitics and posted text and photos on his site  to cover the  mods on that particular amp.
I posted a link for Franklin to take a look see. He was considering the AL 82 suppressors which are for the same tubes
two 3-500s.

Frank
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K1ZJH
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Posts: 3300




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« Reply #17 on: May 27, 2012, 04:20:24 PM »

Hi Frank

Now that  think about it, I remember when Tom posted the story about amp.
I think it was a repair he was doing for someone. Sure wish Tom would come
back and post again.

Pete
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K4RVN
Member

Posts: 30




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« Reply #18 on: May 27, 2012, 07:18:01 PM »

Pete,
I subscribe to what you said about Tom and he is sorely missed. I saw a post not long ago he made. If you read this Tom come on back and keep us straight.

Frank
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KD8MJR
Member

Posts: 5053




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« Reply #19 on: May 27, 2012, 11:21:10 PM »

Hello fellow hams,I want to replace the stock parasitic suppressors in my tl922 and wnt to know what are the dimensions to make new ones and what size resistors ,type ,wattage, ect. I have experienced tube failure in this amp and would like to put in some safe guards if needed before i put in new tubes. The amp has no mods to it.

Since everyone has their popcorn ready to go I will just say that the reason you are getting all the vague responses is because the resident eHam Amp Guru who is a very knowledgeable Ham has had a pretty big disagreement with another Ham that is also heavily into Amp design.  

The core of the argument seems to be the question of whether a suppressor change is really needed or should you instead be spending your time finding out what's really wrong with the Amp versus taking the other approach of using a different designed suppressor that a ham called AG6K has designed.  Both of these Hams are very nice guys, and they have both helped me in the recent past and in the process I have learned a lot about tube amps.

I really think this difference of opinion has been blown out of proportion by some eHam members and even if it’s not I find it hard to believe that time has not healed the wounds.

IMO life is just too short and on top of that we don't have a heck of a lot really smart tube amplifier design engineers left on this planet so one would hope the hatchet is buried or gets buried soon (No Pun Intended  Smiley  )
« Last Edit: May 27, 2012, 11:25:26 PM by KD8MJR » Logged

“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
W1QJ
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Posts: 2598




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« Reply #20 on: May 28, 2012, 04:27:33 AM »

Don't you think that G0HZU (?) put the long time fued to rest after his lengthy and comprehensive experiments on the nichrome suppressor?  His final assesment was that the nichrome reduced the Q about 2 to 5% less than a regular one not the some 500% percent as reported.  There seemed to be no resistance by anyone to his findings including you know who.  If the OP lost  his original suppressors I said I have a set of original ones if he wants them.  Actually I am quite surprised that Tom is gone since since in my mind the fued is over.
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K1HIF
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Posts: 0




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« Reply #21 on: May 28, 2012, 06:10:04 AM »

Here is another picture from www.Somis.org site, Richard Measures AG6K
http://www.somis.org/922.top.jpg

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G3RZP
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Posts: 8123




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« Reply #22 on: May 28, 2012, 07:43:16 AM »

The conventional suppressor has an impedance which tends towards the resistor value as frequency increases. The nichrome suppressor has an impedance which rises as frequency increases, and the Q of that impedance increases. Now that is basic AC theory.

Also basic theory is that for an oscillation to occur, the plate circuit parasitic resonance must be above the grid circuit parasitic resonance. The inductance of the parasitic suppressor tunes the plate parasitic resonance below the grid parasitic resonance and so oscillations cannot occur.

You can find all this theory in Terman's 'Radio Engineering', even in the 1936 edition.

I do not always agree with Tom W8JI, but I certainly do on this subject!
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K4RVN
Member

Posts: 30




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« Reply #23 on: May 28, 2012, 09:02:38 AM »

Franklin,
You might see something useful to you in the post 922 mods on this forum same page. Some good photos on the link posted.
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N3JBH
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Posts: 2358




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« Reply #24 on: May 28, 2012, 09:37:00 AM »

Don't you think that G0HZU (?) put the long time fued to rest after his lengthy and comprehensive experiments on the nichrome suppressor?  His final assesment was that the nichrome reduced the Q about 2 to 5% less than a regular one not the some 500% percent as reported.  There seemed to be no resistance by anyone to his findings including you know who.  If the OP lost  his original suppressors I said I have a set of original ones if he wants them.  Actually I am quite surprised that Tom is gone since since in my mind the fued is over.

Honestly Lou i doubt it very much.  Your absolutely correct that series of test and there outcome should have put this all to rest. But you know Rich he won't let this sleep for long.  How ever i noticed he now preaching the glitch resistor sermon. Maybe he going come up with some super duper 500% improved version of this next  Grin  Oh well i agree it was sad to see 8JI run off. Good thing to remember is every dog has there day. Let's just hope 8JI's day comes soon and he is back in his full and wonderful helping way's   Jeff
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KD8MJR
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Posts: 5053




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« Reply #25 on: May 28, 2012, 04:21:52 PM »

Oh well i agree it was sad to see 8JI run off. Good thing to remember is every dog has there day. Let's just hope 8JI's day comes soon and he is back in his full and wonderful helping way's   Jeff

Huh what happened to W8JI, why did he "Run Off"
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“A lie can travel half way around the world while the truth is putting on its shoes.”  (Mark Twain)
W1QJ
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Posts: 2598




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« Reply #26 on: May 28, 2012, 05:15:01 PM »

Jeff, that whole issue took place on this forum and many probably did not concern themselves with it because quite frankly it was above most of our heads.  Although I followed it closely I could tell that the Brit knew what he was talking about and could not be bulldozed.  I'm convident that his findings were "right on the money" at least to the point to prove that a 500% claim was totally false.  The same sermon is preached to whoever will listen on many other forums.  In short order it will be gone and forgotten and the newbies will again be persuaded.  Tom is gone from here and has joined up on the ameritron amps discussion group.  Unfortunately my email spam guard thinks it is spam so I have to look there to see what is going on.  It barely produces a couple of posts a day.  It's sad, but it seems once Tom leaves he usually does not come back.  You'd think he might still read this forum but not say anything but after that thread you'd think he come in like gangbusters, but no.  That tells me he doesn't even look here anymore. He left amps at contesting years ago and never came back (among others).  I did not see him at Dayton, but I may have missed him.
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N3JBH
Member

Posts: 2358




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« Reply #27 on: May 28, 2012, 06:32:28 PM »

Yep i see Tom on there from time to time. I never been to Dayton and that is sad as it not that  far from here. And a few local's i know quite well make the trip yearly. I have to make that a bucket list thing. But i can't wonder if Tom still reads this and QRZ still. I just think maybe he tired of the bickering on some the posting's. I think if he really wanted to stop being a elmer he taken down his personal web site... What ever reason for his missing in action here i for one realy respected him for his help and explanations.. Jeff
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WB2WIK
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Posts: 21753




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« Reply #28 on: May 29, 2012, 06:52:39 PM »

Damn my popcorn got cold and now I have to make more.

Keep this going a while.  I'm making "stove top" popcorn, it takes longer than microwave.
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N3JBH
Member

Posts: 2358




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« Reply #29 on: May 29, 2012, 09:37:15 PM »

Well Steve we could move this over to QRZ i am sure it get entertaining there  Grin Kind a sad some one got booted when we could use the entertainment.
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