[AMRadio] Ultrasonic feedback


Peter A Markavage manualman at juno.com
Tue Feb 3 15:20:25 EST 2009


 Note: in my text below, I meant to say 12BY7 and 6CA7/EL34s.
Pete
On Tue, 3 Feb 2009 15:16:34 -0500 Peter A Markavage <manualman at juno.com>
writes:
> Pulling the clipper tube just removes the diode action. It doesn't 
> eliminate the pass-through connections. Does this Apache modulator 
> still have two adjustable controls (one labeled Gain on the front 
> panel and one labeled Level, which was behind the key jack)? If 
> Level control (adjusts audio drive to the 12BY7) is set to high,  
> any clockwise adjustment (beyond a few degrees above the off point)  
> of the front panel control can set the second half of the 12AU7 and 
> 12BY7/EL34s into oscillation. Of course, a major modulator mod that 
> might have been done (parts pulled, new parts, changed wiring, etc.) 
> may have turned these two controls into different functions from 
> what they were originally intended to be.
> 
> Pete, wa2cwa
> http://www.manualman.com
> 
> 
> 
> On Tue, 3 Feb 2009 11:11:56 -0800 (PST) John King <k5pgw at yahoo.com> 
> writes:
> > There is NO Clipper circuit in this Apache. The clipper tube was 
> > removed and the tube socket is empty. This seems to be what many 
> did 
> > as a modification. I did have the redrawn schematic showing the 
> mod 
> > but have misplaced it. Thanks for the assistance. 73, john, k5PGW 
> 
> > 
> > 
> > --- On Tue, 2/3/09, Peter A Markavage <manualman at juno.com> wrote:
> > 
> > > From: Peter A Markavage <manualman at juno.com>
> > > Subject: Re: [AMRadio] Ultrasonic feedback
> > > To: amradio at mailman.qth.net
> > > Date: Tuesday, February 3, 2009, 8:54 AM
> > > The front panel "gain" control is for the speech
> > > clipping gain. If you
> > > turn it up too high, depending on the setting of the
> > > "real" audio gain
> > > control which is located behind the key jack, the modulator
> > > will squeal.
> > > This is barring any other electrical or component issues.
> > > 
> > > Pete, wa2cwa
> > > http://www.manualman.com  
 


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