My Ranger used to do a very similar thing, and the fix in that case was to loosen and then retighten all the chassis ground lugs, terminal strip mounts, and the like. Over time the grounds get loose or slightly corroded and signals leak around where they shouldn't.
Steve WD8DAS [email protected] http://www.wd8das.net/ ----------------------------------------------------- Radio is your best entertainment value. ----------------------------------------------------- -----Original Message----- From: John King <[email protected]> To: [email protected] Sent: Mon, 2 Feb 2009 8:56 pm Subject: [AMRadio] Ultrasonic feedback Can anyone direct me to a source of information or a tutorial on Ultrasonic feedback in modulator circuits such as that in the Heathkit Apache. My Apache modulator squeals when the microphone gain is raised and the modulator tubes draw a lot of current. As long as the microphone gain is kept very LOW the current does not take off and there is no squeal coming from the modulator section. I am going to go through the section with a screwdriver and a nut driver to tighten up the grounds to the chassis and tube socket. Ultrasonic feedback is a NEW phenomenon to me. Someone mentioned ferrite beads some time back. Thanks for reading. 73, John, K5PGW ______________________________________________________________ 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 ______________________________________________________________ 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
