Quote:
Originally Posted by jr_tech
If you have no reception below 800kHz both day and night, inspect the tuning cap, it may have a slightly bent plate that is shorting out either the antenna coil or the oscillator coil as the plates are meshed. Inspect it closely as you run the tuning up and down. You may be able to hear a scratchy sound as you tune below 800kHz.
Can you patch the speaker? Elmers glue and tea-bag paper works well.
Of course, recap it and replace the #47 bulb! Why even ask?
jr
PS: I suspect that you are looking for info on the Zenith J420T, (J402T does not exist):
http://www.radiomuseum.org/r/zenith_j420t_ch4j60t.html
Is that it? |
Yes, it is. I had forgotten the exact model number and was wondering why I couldn't find it through Google. Thanks much for the correction.
Thanks much as well for the info on possible causes of no reception below 800 kHz on my Zenith H511Y. I took the radio apart this afternoon and looked at the tuning capacitor; yes, there were at least two plates on the tuning cap rotor that were bent out of shape. I rebent them (carefully!), put the chassis back in the cabinet, and fired it up. One of the first stations I received was WJR in Detroit on 760 kHz, which I had heretofore been unable to tune in on this radio because of the short in the tuning capacitor.
The radio now picks up many more than just two stations; since repairing the tuning cap problem, I found I could receive 740kHz (CFZM, Canada), 850kHz (WKNR, Cleveland, ESPN sports), 970kHz (WFUN, Ashtabula, near Lake Erie, also ESPN), 1100 kHz (WTAM, Cleveland, FOX news/talk/sports), and several other local stations besides, to say nothing of the many out-of-state stations I hear on this set after sundown.
I never hear any stations from Florida, Alabama, Mississippi or other areas of the southern US except Georgia on any of my radios, though; I wonder why. (I live in northeastern Ohio near Cleveland.) I believe there is an ESPN sports talk radio station near Tampa which does just that (cuts power back from 50kW to 0.25 kW or less), and drives people close to the towers crazy during the day when they may be hearing the station not only on their radios, but also in their stereo systems between local AMs, through the amplifiers of the stereo phonograph, even on the burner coils on their electric stove if they have one, or on bedsprings! (I've actually heard of this happening in areas extremely close to high-powered AM radio stations, and I personally had a problem similar to this when, in the early 1970s, I lived within one city block of a local FM station, running 27.5 kW ERP, on 92.3 MHz; the signal would come in on just about everything, even a solid-state stereo tape deck and, amazingly, on channel 6 on my Silvertone roundie color TV.) People living near the towers of then-500kW (in the 1930s) WLW-AM radio in Cincinnati had problems like this and worse whenever the station was on the air. Light bulbs would glow even if they were not in sockets or were in unplugged table lamps, fluorescent bulbs would glow and had to be put in closets when not in use .....
What a mess! I bet Cincinnati's farmers breathed a collective sigh of relief when the FCC finally set the present power limit for AM radio stations at 50 kW, and ordered WLW to shut down its 500kW monster for all time. Of course, people living very close to such towers, or even lower-power ones, may still have problems with the extremely strong signal coming in over their stereo phonographs, lighting incandescent bulbs unintentionally, the station coming in on bedsprings or electric stoves, etc.
Amazing what a little bit of judicious bending of a tuning cap plate can do to bring an old radio back to life. This Zenith was an eBay score about ten years ago. I've liked anything and everything Zenith for years, and in fact had an H511Y just like this one in the early 1970s (it was given to me by relatives who were doing major housecleaning). The one I had got lost many years ago; I missed it, so was very glad to find an identical one on eBay in 2002 or so, the year I joined VK (then AK). There is hardly anything to go wrong with sets like this except bad tubes, although I do hope I don't have to replace the 3-section electrolytic in the power supply, since it is a special non-inductive type that cannot be replaced with a standard, off-the-shelf filter capacitor unless a special modification to the chassis is made (this modification is detailed in a note on the schematic). Why Zenith decided to design the H511s with such an oddball type of filter cap is beyond me.
