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 <[email protected]> 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 <[email protected]> wrote: > > > From: Peter A Markavage <[email protected]> > > Subject: Re: [AMRadio] Ultrasonic feedback > > To: [email protected] > > 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 ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
