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Author Topic: sb200 running 3-500  (Read 1840 times)
KD2DYY
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Posts: 65




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« on: November 06, 2017, 08:17:23 AM »

I should have written it down..... Darn.....
I was talking with a fellow ham quite a while ago and he converted a sb200 to use single 3-500 tube..
since I know it is possible does anybody know of or who they know that has tried this???
getting sick of 572's issues.... never seem to be able to match quality of the Cetrons with the Chinese
replacements..
Hope to hear of 3-500 possibility...

                                                                                  Thanks,
                                                                                  Mike (KD2DYY)
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W1QJ
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Posts: 2602




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« Reply #1 on: November 06, 2017, 08:24:29 AM »

No, it’s not possible in a practical sense,  one good reason is the tube won’t fit.
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K1ZJH
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Posts: 3305




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« Reply #2 on: November 06, 2017, 08:48:03 AM »

I want to see photos...  that would be interesting.

But there are better tube choices and almost all of them would basically
require rebuiding the amp into a homebrew in a Heathkit case.
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KD2DYY
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Posts: 65




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« Reply #3 on: November 06, 2017, 08:58:08 AM »

For Lou(W1QJ)... I was talking with a guy who DID convert to the 3-500 tube....I was not dreaming this up...
I wish I could remember his call sign. Darn it..

                                                                                                         Mike (KD2DYY)
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K8AXW
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Posts: 6312




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« Reply #4 on: November 06, 2017, 09:31:32 AM »

I agree there is no "practical" way to use a 3-500Z in place of the two 572Bs.  I also agree that it CAN be done but as a totally new homebrew project. 

I'd have to have a better reason than just being tired of Chinese tubes to try this.  Like having a junker SB-200 and nothing better to do!
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G3RZP
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Posts: 8123




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« Reply #5 on: November 06, 2017, 09:40:09 AM »

To start with, you need a 5 volt 14.5 amp filament transformer fitted in there. Plus rather more cooling on the tube base than 572Bs need, and probably a filament choke that can handle 14.5 amps rather than 8.
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N2SR
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Posts: 636




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« Reply #6 on: November 06, 2017, 09:43:22 AM »

I'd have to have a better reason than just being tired of Chinese tubes to try this.  Like having a junker SB-200 and nothing better to do!

There's lots of people that decide to do stupid stuff, "because they have nothing better to do."   They make a simple project way more complicated than it should be, end up over their heads, ignore advice from experts, end up blowing stuff up (and seem to be proud of it), and in the end, either it "sorta works," (if they are lucky), or the project never works, and a perfectly good piece of equipment is tossed aside never to work again.  

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If no one is doing it that way, there is a probably a very good reason.
W1QJ
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Posts: 2602




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« Reply #7 on: November 06, 2017, 10:56:00 AM »

For Lou(W1QJ)... I was talking with a guy who DID convert to the 3-500 tube....I was not dreaming this up...
I wish I could remember his call sign. Darn it..

                                                                                                         Mike (KD2DYY)

Ha, maybe the Sb-200 label is the same and that’s about it.  Other than that it isn’t contained in a normal Sb-200 box unless the amp sits upright like a tower computer.  You can’t mount a 3-500 in. Sb 200 unless it’s sei horizontal and it won’t last too long that way.  Love to see pictures for a good laugh.
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K1ZJH
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Posts: 3305




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« Reply #8 on: November 06, 2017, 11:19:45 AM »

The lack of enough high voltage is issue enough to preclude bothering with 3-500Z modification.

There are some Russian tubes that will work, but it still involves some effort and implied experience
working high voltage and RF tank circuits.

http://www.kcdxclub.com/AC0C%20SB200%20Sleeper-v3a.pdf

Pete
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W1QJ
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Posts: 2602




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« Reply #9 on: November 06, 2017, 11:29:58 AM »

Two small GI-7b’s is no problem in an SB200 or even 8874s or the like fit wise.  But really more problem than its worth.  The 3-500 is simply spaced out Looney Tunes.  But then again there are hams that are spaced out Looney Tunes.
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N8CBX
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Posts: 478




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« Reply #10 on: November 06, 2017, 02:44:02 PM »

A single 8875 is a pretty good candidate (or the best candidate). I have seen a SB200/8875 mod done before.
Jan N8CBX
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Dayton Ohio - The Birthplace of Aviation
K1ZJH
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Posts: 3305




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« Reply #11 on: November 06, 2017, 03:05:03 PM »

Well, the tube certainly would be pushed too hard.... but what a waste!  Even would be wasted effort in a SB-220.
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KD2DYY
Member

Posts: 65




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« Reply #12 on: November 06, 2017, 03:20:34 PM »

ok guys.. I give up....... I will just go in the corner and hide...Geez!
Well, you have to give me this... I really stirred up excitement by this post..
I will cease and desist.... But I REALLY do appreciate the interest and the feedback on this
idea... 
  Like I stated in my first post....the contact I had did mod an sb200 to the venerable
3-500 and said it worked well.....   I have no evidence that he was ,in fact, Loony toons..
Thanks again folks it was fun exercise....

                                                           73's to all.
                                                                                  Mike (KD2DYY)                     
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KD2DYY
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Posts: 65




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« Reply #13 on: November 06, 2017, 03:24:49 PM »

ooops  I meant to type  LOONEY TUNES.....
Spelling is another fault I admit to.

                                                              Mike (KD2DYY)                                                     
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K1ZJH
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Posts: 3305




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« Reply #14 on: November 06, 2017, 03:36:06 PM »

No one said it couldn't be done, but whether it is practical to do so is another matter.
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