Zenith C845 - FM works, no AM

[Jeffhs]

Originally Posted by Reece

Garbled and poor reception on AM with a new loop, and the radio having worked OK on AM before that, sounds like an open AM antenna loop. Check the loop for continuity with your DVM.

Also: work the bandswitch back and forth a dozen times which will tend to clean it even without any cleaner. Clean the pins of all the RF and IF tubes, one at a time, with some rubbing alcohol if you have nothing better, or even a little WD-40, applied to all pins sparingly with a cotton swab, and then while the pins are still wet plug the tube in and out of the socket several times to clean.

I will bet on the open loop and the dirty contacts. Good luck!

Reece,

Thanks much for the advice.

I found the problem tonight; it was the loop, which was open. There is a very small terminal strip on the loop to which its fine wire leads connect; one lead was disconnected from its terminal, effectively causing an open circuit. I took the lead from the open side of the loop and connected it to the AM tuning capacitor, connected the other (low or ground) side to the feedthrough capacitor terminal on the chassis, turned on the radio to AM, and it worked.

Amazing, the problems one little, teeny-tiny (and all too easy to overlook) open connection can cause! The only other problem I have now is what seems to be a poor contact on the band switch, resulting in intermittent FM reception. I'll order a can of Deoxit tomorrow on Amazon.com (thanks to jr_tech for the link) and give that switch a cleaning, which will probably be the first really good cleaning it has had in over a half-century. I'll clean the radio-phono selector switch too, while I'm at it.


Thanks again, Reece, for the advice on checking the loop. I had been looking everywhere else (except under the chassis) for the problem; I had mistakenly assumed that since the loop looked OK, it would work--I didn't think to look at the terminals until tonight.