Zenith H511Y reception problems

[wa2ise]

Originally Posted by Jeffhs

Someone on another antique radio forum (not ARF) told me shortly thereafter the rectifier tube will burn out soon if the radio is operated without the pilot light in the circuit. My question: Is the #47 pilot light in the H511 radios an integral part of the power supply? It must be, if the rectifier tube glows red if the bulb is burned out or is otherwise out of the circuit, but I don't see how, unless the bulb is part of a voltage divider or serves some other function in the B+ power supply.

Thanks much.

Answer is yes. The pilot lightbulb is wired in parallel with a portion of the 35W4 rectifier heater. Off the hot side of the incoming powerline are connected the pilot light and the 35W4 heater portion mentioned above. Then the pilot light and heater tap in turn connects to the 35W4 rectifier plate. Thru the bulb and heater portion is about 300ma average of current, 150ma for the heater string, and the rest feeds the rectifier and in turn becomes the set's B+. The heater portion will get unhappy with all the 300ma. I think Radio Shack still sells #47 bulbs.

[Jeffhs]

Originally Posted by wa2ise

Answer is yes. The pilot lightbulb is wired in parallel with a portion of the 35W4 rectifier heater. Off the hot side of the incoming powerline are connected the pilot light and the 35W4 heater portion mentioned above. Then the pilot light and heater tap in turn connects to the 35W4 rectifier plate. Thru the bulb and heater portion is about 300ma average of current, 150ma for the heater string, and the rest feeds the rectifier and in turn becomes the set's B+. The heater portion will get unhappy with all the 300ma. I think Radio Shack still sells #47 bulbs.

This is all well and good, but I am much more interested in why the radio doesn't pick up more stations than it does in the daytime (as I mentioned, it only gets two stations, and there is no reception below about 800 kHz). I seriously doubt there's anything wrong with the radio if it gets all sorts of stations after sundown, but if this is the case then I would think I'd be hearing every major Cleveland station in daylight hours as well as the two I mentioned (this area has about a dozen AM stations, not counting small low-power ones, one of which went silent about five years ago, in suburbs and small-town "exurbs" which are not considered part of the metropolitan area). I am thinking just about every paper capacitor in my set is bad, since the H511 series was introduced in 1951, sixty-plus years ago.

I also mentioned a Zenith AM-shortwave battery set (farm radio?), 1952 vintage, similar in appearance to the H511. I spent literally hours last night on Google and even eBay looking for information on it (I am interested in this model because of its similarity to the H511), but couldn't find anything. Were these radios any good on shortwave or just so-so? I would think the latter, since the radio was primarily designed for AM broadcast reception.

Also, what types of batteries did this radio use, and where were they stored inside the set? The cabinet doesn't look anywhere nearly big enough for the large 90-volt B battery needed for the plate supply or the smaller batteries needed for the filaments. As large as the H511 cabinet is, it almost certainly isn't big enough for a combo AB battery pack either. The chassis sits on the floor of the cabinet with no space, that I can see anyway, for batteries underneath it. Unless the battery-powered AM-SW version's cabinet is actually larger than that of the line-operated H511s, I cannot imagine where the batteries would be stored. Having a large battery pack sitting alongside the radio wouldn't settle well with most people, unless the batteries were in a separate case that could be hidden under the table on which the radio sits.

Also, the schematic you included with your response is not specifically for the H511. I realize that diagram is for generic 5-tube AM radios (commonly known as AA5s), but is it close enough to the H511 circuit design as to be usable with the latter? I am asking because the H511 has at least one circuit refinement most AA5s do not have -- namely, a tone-compensation network in the audio stage, before the output tube. This probably has no bearing on the configuration of the power supply (when you've seen one AA5 power supply, you've seen them all, except for those weird series-parallel arrangements sometimes found in high-end sets; I have a Zenith MJ1035 with such a filament configuration), but I mention it as a point of interest.


Thanks much.

[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?

[wa2ise]

As jr tech mentions
The cap on the AVC line may be leaky and interfering with the automatic gain function. Just change one wax cap at a time, so you don't forget where its replacement connects to. Change the electrolytic caps too.

Thought comes to mind: check that the antenna circuit doesn't have a broken wire. Though I'd think that the 12BE6 grid would not be biased properly and the set would be deaf.

Though it's way down on my list of suspects today, a weak IF tube or 12BE6 could be the problem. But I always blame wax caps first, just replace them on sight.

[Jeffhs]

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.

[jr_tech]

Originally Posted by Jeffhs

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.)

While it may be fun and nostalgic to attempt serious DXing with small vintage analog-dial tube-type table models, I suspect that you need a bit more selectivity and sensitivity than these sets can provide. Have you attempted AM DXing with your ICOM IC-725?... it should be quite a good performer!
Pip, the DX cat says that ICOMS are purrrrrty good!

jr

This station list might be helpful:

http://www.ac6v.com/clearam.php

Happy DXn!

[Jeffhs]

Originally Posted by jr_tech

While it may be fun and nostalgic to attempt serious DXing with small vintage analog-dial tube-type table models, I suspect that you need a bit more selectivity and sensitivity than these sets can provide. Have you attempted AM DXing with your ICOM IC-725?... it should be quite a good performer!
Pip, the DX cat says that ICOMS are purrrrrty good!

jr

This station list might be helpful:

http://www.ac6v.com/clearam.php

Happy DXn!

My DXing days ended when I moved into an apartment 12 years ago. There is no way I can put up a decent antenna -- for AM, FM, TV, amateur radio or anything else -- in an apartment building (lease restrictions). I cannot use my Icom ham rig anymore for the same reason, so I put it in a box and forgot about it.

BTW, even when I had a decent antenna for HF and broadcast at the house where I used to live, I never heard any AM radio stations from Florida or anyplace else (except the Atlanta, Georgia area) in the southern United States, let alone the Southwest or the West Coast. The closest I ever came to hearing AM radio from the Southwest was when I received a 50kW station from Dallas, and one Sunday night when I heard KOA-AM radio in Denver, the latter after a local Cleveland station had signed off for technical maintenance. I don't remember what radio I heard the Dallas station on, but the Denver station was received on the AM tuner of a Zenith integrated 4-mode stereo system I owned at the time (1980s). Both radios had indoor antennas.

I think my DXing days are over as well because of the noise level in this apartment building. I often hear a loud noise on the AM broadcast band at certain points that sounds like the horizontal oscillator in old (pre-digital) TVs, that masks any stations I may otherwise be able to hear on those frequencies. This building has twelve units, every one of them occupied, so my hands are tied -- I can't tell people not to watch TV just so I can hear a few distant AM radio stations. (They probably wouldn't understand anyway.)

Finally, I realize my DXing problems would be solved if I moved into a house far away from any source of interference, but that too is out of the question (very long story and off-topic).

[jr_tech]

I must have misunderstood your question... It appears that you have answered it better yourself. If you haven't been able to DX for 12 years, because of your living situation, it appears that it would indeed be very unlikely that you would hear DX stations. Perhaps I am confused?

jr