Zenith 723R on the fritz - Printable Version
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Zenith 723R on the fritz - Paul Philco322 - 08-24-2012
Hi Gang:
I have a neat little Zenith 723R, am/fm. Always a good sounding set, but is developing tons of static on AM picks up only 1-2 stations on AM where as before it was quite sensitive.
It has had capacitors switched out, resistors checked. Is there a tube in these little guys that has more impact on AM that could be a likely culprit? Still plays very well on FM. Any suggestions are appreciated.
Paul
RE: Zenith 723R on the fritz - Ron Ramirez - 08-24-2012
It sounds like your set may be suffering from silver mica disease. What you describe (lots of static on AM) is the classic symptom.
What this means is, the mica capacitors in the AM IF transformers have gone bad, and will require replacement.
This, from what I have read (I've never done this repair), is not easy, but not terribly difficult if you are very careful.
RE: Zenith 723R on the fritz - codefox1 - 08-24-2012
Yup. Cut 'em out and tack good ones in. Use Silver Micas.
RE: Zenith 723R on the fritz - Paul Philco322 - 08-24-2012
Ugh.... I have not had this crop up before, thanks for the feedback.
Paul
RE: Zenith 723R on the fritz - Arran - 08-25-2012
It could be silver migration, depending on whether this uses slug tuned IF cans, but it may be just be intermittent contact. I had to renovate a mini IF can from a 50's radio where that was the problem, not much static but I did experience a volume drop when one of the IF cans got bumped. Before performing major surgery try giving the band switch a good cleaning as well as the tube socket contacts. If it does turn out to be bad micas in the IFs make sure you find out the correct values first, they are not all the same. You also do not need to use silver mica caps to replace the originals, precision ceramics will also work, are easier to find in any size, and are much cheaper.
Regards
Arran
RE: Zenith 723R on the fritz - Paul Philco322 - 09-06-2012
Poor tube socket connections on input converter tube pins, bandswitch to get a cleaning. No silver migration issue! Should be good to go for a while. It is a nice sounding set, follows me around the house.
Thanks for the input gang, thanks Arran.
Paul