Well, I got the hum problem cured. I feel so stupid. Somehow when I removed the audio output transformer feedback wire from the filter cap, I reconnected it to the B+. (Hint- When you are really sick with the flu and running a 104 temp,- do not try to work on equipment!) Oscillator problem was solved . Oscillator was cutting out due to low filament voltage.
Frank -- HQ Electronics 218 N 1st St Shelton WA 98584 360-426-3336 (Shared phone and fax) http://www.hqelec.com ----- Original Message ----- From: "Frank Burnham" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, January 22, 2004 7:27 PM Subject: [Techs] Zenith help needed- Transoceanic H500 > Make: Zenith > Model H500 > In Sams but didn't bring home the # with me tonite. > Problem Weird hum > > Hum like 60 cy- varies with volume. Tune radio on local starion on AM ( Yes > there is a problem with AM tuning too, only gets 1 station the local one); > When volume control at min massive hum- almost identical to bad filter- in > audio. As volume control increased, hum gradually fades and station comes in > clear. Several stations on SW come in also. > Can inject hum with finger on slider of vol control, and hear the change > between it and the hum present. > > Replaced the main filter cap in the radio. Triple checked the wiring and > grounding of the filter against the schematic in Sams. Verified 2x all > hooked up right. Checked the filter caps prior to installing. Note- > previously the selinium rect was replaced with a silicon diode(- & subbed > the diode too). Checked the B+ for ripple- maybe 4 VAC on the input cap and > 2V or less max on the output filter. The only thing I can think of is an > open gnd, but have ohm'd all of them and even run a jumper wire as a test. > > Have also replaced all the caps in the volume control/ tone control network > and 1 resistor in the IF, which had almost doubled in value. > Tubes check ok on store tester Plate and screen voltages appear almost > proper on the tubes. > > > What the heck am I missing??? Could this radio be in some strange > oscillation? > Any help appreciated, > Frank > Dr. Digital > > > > _________________________________________ > Please include original text when replying to this email. > Once you get your unit repaired, please post the fix to the group. > Order your tech repair CD today, Version 3.0 only $49.00-more monitor > tips-user friendly program. > [EMAIL PROTECTED] www.tech-repair.net > ______ > Techs mailing list > [EMAIL PROTECTED] > http://intrepid-video.com/mailman/listinfo/techs_intrepid-video.com > Go to the link above and scroll to the bottom to enter your email address > _______________________________________________ Tech Repair CD...order your just $49.00 plus shipping...One year of updates free. www.intrepid-video.com www.tech-repair.net Techs mailing list [EMAIL PROTECTED] http://intrepid-video.com/mailman/listinfo/techs_intrepid-video.com
