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 Post subject: Zenith K-731
PostPosted: Jun Thu 11, 2009 9:43 pm 
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Joined: Jun Thu 11, 2009 9:32 pm
Posts: 3
I'm not a collector but today I came across a vintage Zenith radio Model K-731 for sale a at thrift store. The sound quality was very good and I was going to purchase it but did not do so due to concerns about getting parts should it cease to operate. Can anyone tell me how readily available replacement parts would be should I need them? Also, what would be the ball park value of this radio based upon it being in very good condition.

Vince V.


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 Post subject:
PostPosted: Jun Thu 11, 2009 10:10 pm 
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Joined: Dec Sun 07, 2008 7:05 am
Posts: 4357
Location: Meridian, MS 39307
The main things that give trouble in those are capacitors, the selenium rectifier, and tubes. The selenium rectifier would need to be replaced with a modern silicon diode and the tubes and caps are very much available today. I think the "book" price on the K731's is around $45. I've seen some go for more on epay and I've seen some for less. IMHO, I would probably not pay over $45 for one of these because I believe they are still fairly common and they can still be bought for cheap from the right person. So, if the one at the thrift store was under $45 and in good shape, I'd probably get it.


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PostPosted: Jun Thu 11, 2009 10:33 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 8715
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
A Zenith K731 is a fairly recent model tube radio. The caps are not going to be much of a problem. As I recall, aren't they mostly ceramic disc or tube? I wouldn't even bother recapping anything other than the power supply and only if it needs it. The vacuum tubes, if they fail at all (they rarely do) are commonly available.

The biggest problem with these is going to be the silver mica caps in the IF transformers. Repairing them is not a big deal, just a bit of work, especially the first FM IF because it's half buried under the FM tuner.

Once repaired they are nice players.

What are they worth? In my humble opinion, I wouldn't pay any more than about $50 and ONLY if it's in really nice shape.

cheers

John


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 Post subject:
PostPosted: Jun Thu 11, 2009 11:14 pm 
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Joined: Jan Sun 04, 2009 6:43 pm
Posts: 890
I have several of these. There are 2 cabinet styles - a "modern" and a "colonial". The insides are the same.

There are only about 4 plastic caps to replace, and 3 electrolytics in the power supply (80, 60 and 40 mfd). The rest are ceramic discs. The tubes are all common and cheap. The selenium can be bypassed with $2 worth of parts from Radio Shack.

Mine all played fine and sounded great when I got them, but I changed the caps and selenium on them just for the experience. The K731 makes a great "first radio" to work on. The chassis is not cramped, there is plenty of room to work.

I paid between about $15 and $40 each for them on eBay. They are very common on eBay. The $40 one is in like new condition - no scratches in the wood, chrome on front all there and shiny, plastic knobs not faded, grill cloth not loose, faded or torn, chassis is very clean. It basically looks brand new.

A good daily use radio that does not run too hot. Has 2 speakers and so has good sound. The only downside is that the tuning dial is not lighted.


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 Post subject: Re: K731
PostPosted: Jul Wed 01, 2009 9:38 pm 
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Joined: Jun Thu 11, 2009 9:32 pm
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Thanks, radiotvnut!

radiotvnut wrote:
The main things that give trouble in those are capacitors, the selenium rectifier, and tubes. The selenium rectifier would need to be replaced with a modern silicon diode and the tubes and caps are very much available today. I think the "book" price on the K731's is around $45. I've seen some go for more on epay and I've seen some for less. IMHO, I would probably not pay over $45 for one of these because I believe they are still fairly common and they can still be bought for cheap from the right person. So, if the one at the thrift store was under $45 and in good shape, I'd probably get it.


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 Post subject: Re: K731
PostPosted: Jul Wed 01, 2009 9:43 pm 
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Joined: Jun Thu 11, 2009 9:32 pm
Posts: 3
Thanks Naddy69!

Naddy69 wrote:
I have several of these. There are 2 cabinet styles - a "modern" and a "colonial". The insides are the same.

There are only about 4 plastic caps to replace, and 3 electrolytics in the power supply (80, 60 and 40 mfd). The rest are ceramic discs. The tubes are all common and cheap. The selenium can be bypassed with $2 worth of parts from Radio Shack.

Mine all played fine and sounded great when I got them, but I changed the caps and selenium on them just for the experience. The K731 makes a great "first radio" to work on. The chassis is not cramped, there is plenty of room to work.

I paid between about $15 and $40 each for them on eBay. They are very common on eBay. The $40 one is in like new condition - no scratches in the wood, chrome on front all there and shiny, plastic knobs not faded, grill cloth not loose, faded or torn, chassis is very clean. It basically looks brand new.

A good daily use radio that does not run too hot. Has 2 speakers and so has good sound. The only downside is that the tuning dial is not lighted.


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 Post subject:
PostPosted: Jul Wed 01, 2009 10:39 pm 
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Joined: Jan Thu 01, 2009 3:22 pm
Posts: 24
Location: Buffalo NY
Make sure the electrostatic tweeter (the smaller square speaker) is in place. I've got a couple of these and agree they sound great and don't need a lot of service. One we use is unmodified and one has had the Se rectifier, electrolytics, and a few other caps replaced. Adding some series resistance with the Si diode keeps the voltages about right (I use a couple watt 82 ohm resistor--a 100 ohm wirewound is probably fine).


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 Post subject:
PostPosted: Oct Thu 01, 2009 9:15 pm 
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Joined: Oct Thu 01, 2009 8:37 pm
Posts: 6
Location: Fairport Harbor, Ohio
I also have a K731 in the Colonial style mahogany cabinet, and like it a lot. Excellent sound and build quality (typical of the original Zenith Radio Corp. of Chicago). I've only replaced one tube in my set since scoring it on eBay several years ago; other than that, the radio has required no service whatsoever, although one of these days I'm going to replace the selenium rectifier with a modern silicon diode. I intend to hold on to this set as long as it works, as they don't make them like that anymore. I also have a C845, MJ1035 and several other Zenith radios in my collection; I'd be looking for more such sets from the '50s-'70s (my favorite Zenith radio era), but, unfortunately, my budget won't allow it.

73,

Jeff Strieble, WB8NHV
Zenith radio collector-restorer since 2002
Fairport Harbor, Ohio USA


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 Post subject:
PostPosted: Oct Thu 01, 2009 11:04 pm 
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Joined: Jan Sun 04, 2009 6:43 pm
Posts: 890
Jeff, your collection sounds much like mine. I have 3 K731s, 1 or 2 each of the C845/H845/X338/X337 series, and 4 MJ1035s.

I also like this era of Zenith because of the build quality, the sound quality and the ease of service. They are all fairly modern so there are no exotic/expensive parts or tubes. You can run them daily without fear.

I have at least one in every room of the house. 8)


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 Post subject: Re: Zenith K-731
PostPosted: Feb Wed 04, 2015 7:15 pm 
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Joined: Feb Wed 04, 2015 7:05 pm
Posts: 1
Im new to this site, and I found this post via a google search. I have a question on the Zenith K731, actually a couple of questions.

I have one I am thinking about sending out for repair, but I wonder if it's worth it since folks don't seem to think it's worth that much.

I am getting estimated in the $300 + range for a complete once over, rectifier, caps, cleaning of the pots, replace the dial string, replace any out of spec resistors, etc.

Now I wonder if maybe I just replace the electrolytics, the rectifier, and have the tubes tested, it might cost a lot less. I have done some work on tube amps but not tube radios, so I know my way around some of the circuits, except for the FM and AM portion of the radio.

What are your thoughts, go DIY, or go for the full job?

Thank you for your time.


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 Post subject: Re: Zenith K-731
PostPosted: Feb Thu 05, 2015 1:22 am 
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Joined: May Sat 06, 2006 4:03 am
Posts: 3606
Location: ZIP 23831 South of Richmond, VA 25 miles down the pike.
Chuck, You are talking about a table top radio from early 60's.
Bill J.


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 Post subject: Re: Zenith K-731
PostPosted: Feb Thu 05, 2015 3:16 am 
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Joined: May Mon 30, 2011 10:12 pm
Posts: 1508
Location: Glendale, CA
Chuck,

I could be wrong, but to me, $300.00 sounds like a lot of money. If you have some experience with tube amps, you shouldn't have any problem working on your Zenith.

You can check out Phil's Old Radios at http://www.antiqueradio.org/FirstStepsInRestoration.htm.

To buy replacement capacitors check out the advertisements from the suppliers on the right of this screen.

The guys here are extremely knowledgeable about radio restoration. I would start a new topic in the electrical/mechanical repair section of this website and follow their excellent guidance.

Good luck, Tom

_________________
"A challenge to be met, rather than an obstacle to avoid." - Mr. Data


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 Post subject: Re: Zenith K-731
PostPosted: Sep Fri 13, 2019 12:58 am 
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Joined: Sep Fri 13, 2019 12:54 am
Posts: 1
I just picked one of these up today for $35. It works and sounds great with 1 minor issue. It sounds like one of the speakers may be blown. If I turn the tuning knob down (which seems to boost the bass), I get this vibration/reverb ... kind of a humming in the middle of the front. So can these speakers be swapped out if I find one or more damaged?

Side note... I'm a n00b to the site, I just joined, and this is my first post. Thus begins my journey as a collector. :D


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