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  #1  
Old 06-03-2009, 01:54 AM
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chasaboo chasaboo is offline
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Hi new guy here with a Zenith Automatic Frequency Control radio

Well I'm testing old radio waters and I bought a Zenith Automatic Frequency Control radio. I've been on this website for years and had no idea there was a forum devoted to antique radios, great stuff.

It's funny but when I took the plunge and bought this radio I thought it would probably be a transistor radio but it takes about 20 seconds or so for the radio to warm up so I'm guessing it's actually tubes.

The funny thing is I haven't opened it up yet to see what's inside. I'm a little stymied by its construction. It's a bit like a green plastic bucket that sits on its side. The face plate actually covers what would be the top of the bucket. I see two screws on the bottom and two screws in the back but I haven't figured out what these screws do or how to get inside.

I'm a little afraid to try and open it for fear of breaking or killing the thing. It plays reasonably well and tunes in my favorite classical music station quite nicely.

Can a radio such as this have a big improvement in sound by replacing tubes and capacitors or would I have to go so far as replacing the speaker? I realize it's not an audiophile piece of equipment but I like the old girl and was wondering if the sound could be tightened up a little. Below is a picture of this model of radio I have but it's not the exact one I have as my camera is traveling somewhere in Asia right now.

Thanks for any thoughts and advice you might have.

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  #2  
Old 06-03-2009, 03:59 AM
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Hemingray Hemingray is offline
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These Zeniths actually sound rather nice. Yours is indeed a tube type.
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  #3  
Old 06-03-2009, 12:44 PM
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Jeffhs Jeffhs is offline
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I second Hemingray's comments. Zenith made some excellent radios in their day, until they got out of the radio business in the early 1980s (1982, to be exact). I have three Zenith wood-cabinet sets (MJ1035, C845, K731) and a high-performance 13-transistor Zenith portable (R-70) that work well and have excellent sound, although as I write this the MJ1035 has a problem with the volume control--but when it works, it sounds great.

I'd leave the original tubes in your radio if the set works.

Replacing capacitors, especially the three-section electrolytic in the power supply (the latter is almost always bad in very old radios and is quite often on the verge of failure in 1950s-'60s receivers) in old sets is standard procedure when restoring them. Replacing the caps in and around the audio stages can improve the sound by altering the audio response curve. I would be careful not to put too large or small a capacitor in these circuits, the reason being that too small a cap will emphasize higher frequencies to the hilt and then some (the audio will sound abnormally shrill); too large a cap will overemphasize the lows, resulting in an excessively bassy sound.

If you have the room in the cabinet and can find a larger speaker, by all means go ahead and replace it--you have nothing to lose and everything to gain in terms of improved sound quality. Note that you can always replace a four-ohm speaker (for example) with an eight-ohm one with no fear of damaging the radio's output stage (the only thing you will lose is a little volume), but not vice-versa. Replacing an eight-ohm speaker with a 4-ohm one or less will damage the output transformer and/or other parts of the radio. The best thing is to replace the original speaker with one of the same impedance; the use of higher-impedance speakers is an emergency procedure, to be used when or if the proper speaker is unavailable.

Good luck. I'm not really all that familiar with your particular Zenith radio, but the company's sets from the '40s through the '60s were excellent radios, with no production shortcuts. You won't be disappointed once you get your set working. These radios, as I have mentioned many times in this forum, represent a level of sound/build quality which we will never see again, in this age of cheap plastic one-chip headphone stereos. Once you get that set singing again, hold on to it. As I have also said (and believe with all my heart, as I am a Zenith radio collector and have a great deal of respect for the original Zenith Radio Corporation of Chicago), they don't make them like that anymore.
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Old 06-03-2009, 04:40 PM
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Hemingray Hemingray is offline
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I'm not too certain, but if it's like my white Zenith radio (which has this same dial and knob layout), it probably uses a 6BJ6 for an RF amplifier. These guys can pick up FM real good. great with AM too.
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Old 06-04-2009, 12:36 AM
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I've got one of those sets buried here somewhere in need of restoration. If that radio uses a selenium rectifier (fin looking device), it should be replaced with a modern silicon diode (something like a 1N4007) and a voltage dropping resistor. The electrolytic and paper capacitors should be changed. By the time this radio was made, many paper caps were being made with so called sealed plastic housings. I find that these are just as prone to leakage as their '30's wax covered family members.

Lastly, there is one thing that you should be aware of. This radio likely has a "hot" chassis. What that means is that one side of the AC line is directly connected to one side of the chassis. This poses a serious shock or electrocution hazard. The safest way to work on one of these is to use an isolation transformer. If one is not available, use extreme caution and don't allow any part of your body to touch anything that might have a path to ground while working on the chassis. Try not to even touch the chassis while it's powered up if an isolation transformer is not used.

Most transformerless sets that you find will either have one side of the AC line connected directly to the chassis or have one side of the AC line connected to the chassis thru a capacitor. Zenith seemed to love the direct approach. Many of their tube radios had a printed warning on the back cover stating that one side of the AC line is directly connected to the chassis. This goes for tube and early solid state models.
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Old 06-04-2009, 08:52 AM
cpacamper cpacamper is offline
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http://antiqueradio.org/welcome.htm

Click on the link for beginners. This is a very good, informative website for those who want to learn about old radios. Be forewarned, once you start, casual interest quickly becomes avid hobby
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Old 06-04-2009, 09:53 AM
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Quote:
Originally Posted by cpacamper View Post
http://antiqueradio.org/welcome.htm

Click on the link for beginners. This is a very good, informative website for those who want to learn about old radios. Be forewarned, once you start, casual interest quickly becomes avid hobby
That bug already bit me back in high school.
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Old 06-04-2009, 10:07 AM
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Sandy G Sandy G is offline
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Damthaings TALK to you...You'll see one, sittin' forlornly in an antique/junque/shoppe somewhere, & it'll look at you sad, & say- "Take me home w/you, Mister, please ? I'm just a nice li'l ol' All-American Five, I'd be a GOOD radio, always give you Good News...Whaddya say, pal ? Come on, you KNOW you want me, I'm kinda cute, & with a wipedown w/a damp, warm rag, I'll look like I was new again...Come on, pal, let me come home with, OK ?..." And dammittall, I'll end up bringin' ANOTHER one home...(grin)
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Old 06-04-2009, 12:47 PM
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You summed it up perfectly Sandy! They do seem to have consciousness.

John
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  #10  
Old 06-04-2009, 11:58 PM
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Tony V Tony V is offline
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I have several of these in different styles with the same chassis. One of the best table FM radio's of the day. All of mine played great from the start but a recap did improve the sound quality on a couple of them. Nice Find!
-Tony
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  #11  
Old 06-05-2009, 06:23 AM
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Hemingray Hemingray is offline
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Quote:
Originally Posted by Sandy G View Post
Damthaings TALK to you...You'll see one, sittin' forlornly in an antique/junque/shoppe somewhere, & it'll look at you sad, & say- "Take me home w/you, Mister, please ? I'm just a nice li'l ol' All-American Five, I'd be a GOOD radio, always give you Good News...Whaddya say, pal ? Come on, you KNOW you want me, I'm kinda cute, & with a wipedown w/a damp, warm rag, I'll look like I was new again...Come on, pal, let me come home with, OK ?..." And dammittall, I'll end up bringin' ANOTHER one home...(grin)
I have that same problem! Even if it is just some dinky AA5 radio.
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Old 06-05-2009, 07:32 AM
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Well, misery loves company, I guess...Good to see I'm not the ONLY one that thease damthaings "talk" to...(grin) But wait til you run acrost a Grundig, SABA, Emud, or Nordemende...They ORDER you to take 'em home !!
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Old 06-05-2009, 08:24 AM
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Quote:
Originally Posted by sandy g View Post
well, misery loves company, i guess...good to see i'm not the only one that thease damthaings "talk" to...(grin) but wait til you run acrost a grundig, saba, emud, or nordemende...they order you to take 'em home !!
LoL!!!! My Grundig ordered me to bring it home, now it orders me to listen to it once in a while. Nice Zenith BTW, you will have many good years of listening from that one. Also, get any of those white porcelain caps out too, (if it has them) they like to explode sometimes. Usually when rap noise comes on.
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Last edited by zenithfan1; 06-05-2009 at 08:31 AM.
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  #14  
Old 06-05-2009, 08:45 AM
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tomrich22 tomrich22 is offline
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Nice score on the Zenith radio. I had a K731 that I bought brand new when I was a teen in the 60's. I'll send a pic later. My aunt and uncle had one of those C845 or H845 like Jeffhs. These baby's could pull in the stations with just the cord antenna! I remember listening to my aunt and uncles while baby sitting for my cousins and pulling in stations from Chicago from Grand Rapids MI (thats about 100+ miles away) with just that cord antenna. They don't make um like they use too!
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  #15  
Old 06-05-2009, 07:45 PM
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tomrich22 tomrich22 is offline
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Here is the pic of my Zenith K731
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File Type: jpg IMG_0486.jpg (110.4 KB, 24 views)
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