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Author Topic: Multiphase 20A Exciter  (Read 1141 times)
WA2DTW
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Posts: 91




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« on: February 24, 2008, 06:32:03 AM »

Recently re-acquired a Multiphase 20A exciter (I had one as a child).   There are a few tubes missing, but also something called QT-1 in an octal socket.  It is not clear from the manual or schematic what "QT-1" is.  Does anyone know?  Is it something that can be built or replaced?
Thanks and 73
Steve WA2DTW
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KA5N
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Posts: 4380




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« Reply #1 on: February 24, 2008, 08:04:16 AM »

The QT-1 is the "anti-vox" circuit for the 20A.  Keeps signals from the receiver's speaker from activating the VOX (without it you have to use headphones if you use VOX).  The manual on the BAMA site doesn't show the inner workings of the QT-1.  I had a 20A back in the 1960's which had a QT-1 and if I remember correctly it was a sealed up metal can.  Maybe you can find a schematic somewhere or design your own circuit.  Since I perfer to not use VOX I wouldn't worry about it as the 20A will work well without it.  No QT-1, want VOX?  Wear cans.
Allen
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WA2DTW
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Posts: 91




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« Reply #2 on: February 24, 2008, 11:09:22 AM »

Many thanks, Alan.  Glad the rig will work without it.
I can live without VOX.  
73
Steve WA2DTW
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KL7AJ
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Posts: 340


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« Reply #3 on: February 25, 2008, 08:57:11 AM »

Whew!   I almost thought you said the 2Q4 was missing@!  This was the audio differential phase-shift module....very hard to duplicate!  

You have a gem there.  Give it love.

eric
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WA2DTW
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Posts: 91




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« Reply #4 on: February 25, 2008, 12:24:07 PM »

Thanks, Eric
I had this rig in the early 1960's, when I was quite young.  Stupidly I got rid of it in the '80s.  So this was too tempting to pass up.
73
Steve WA2DTW
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