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Author Topic: Johnson Viking II modulation tube plates  (Read 1434 times)
K7MDO
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Posts: 325




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« on: October 02, 2012, 11:55:10 AM »

I kind of got in a hurry taking apart a recently acquired Viking II to clean up the chassis.  I unplugged the plate cap leads on the two 807's without marking "which lead went to which tube"....  in looking at the circuit diagram is is not easy to tell which lead went to which tube.  I think it may not matter but want to be sure.  Anyone with history on this problem?  One lead is "greenish" and the other "yellowish" in color.

73, thanks, Tom
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W9GB
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Posts: 2597




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« Reply #1 on: October 02, 2012, 11:59:18 AM »

Mark Bolton, KA4CID took photos of his Viking II restoration
http://ka4cid.blogspot.com/2011/07/restoration-of-johnson-viking-ii-my.html

http://ka4cid.blogspot.com/2012/04/its-been-long-time-since-ive-updated-my.html
« Last Edit: October 02, 2012, 12:01:47 PM by W9GB » Logged
N2EY
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Posts: 3835




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« Reply #2 on: October 02, 2012, 12:01:24 PM »

It doesn't really matter unless and until you get to the point of adjusting the audio phase for best upward modulation.

73 de Jim, N2EY
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K7MDO
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Posts: 325




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« Reply #3 on: October 02, 2012, 03:56:53 PM »

Well I am certainly not there yet.... the set I am working on is a CD version and I have already replaced caps and resistors (using, btw, the new Hakko 808 solder sucker that really works!!)  but have decided to clean the chassis and repaint the front before it gets lit off on the scope.  Thanks for the links and thoughts.  73, Tom
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W8JI
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« Reply #4 on: October 02, 2012, 06:03:40 PM »

I modified the clipper in my Valiant so it only clips one peak. Then I put the plate caps on so the peak it clips is the negative peak.

The result of this is the 6AL5 clipper tube only limits negative peaks. 
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K7MDO
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Posts: 325




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« Reply #5 on: October 02, 2012, 07:48:10 PM »

It sounds like a very similar circuit for the Viking II.  The CD version has the 6J6 clipper tube circuit whereas the regular Viking II does not have the tube or circuit.  At least not on the ones I have seen on the internet.  I will wait to get the case refinished and the reassembly done before I begin the testing ....  but assuredly I will be looking at the peaks to see the clipping.  Thanks Tom, Tom
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