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 Post subject: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: May Thu 09, 2019 1:34 pm 
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Joined: Apr Sat 27, 2019 7:12 pm
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Location: Attleboro, MA
Long shot I know....but is there anyone in the southeastern Massachusetts area that is knowledgeable about TV restoration, that would like to assist someone with little experience that wants to learn, with a restoration project?


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: May Thu 09, 2019 11:54 pm 
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Hi, Jon.... I restored that very model about 30 years ago. I'm a long way from you, but maybe I can help you get it going.

First of all, find out if the picture tube is good. There may be an antique radio club in your area, and a club member might be able to test it for you.

Secondly, DON'T plug it in and try to operate it! All of the electrolytic capacitors are sure to be bad, and all of the molded paper capacitors are going to be leaky. If the picture tube is good, then you can start with electronic restoration.

That set has the 28F20 chassis, which was their first one in regular production.

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Tim KA3JRT


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: May Fri 10, 2019 10:17 pm 
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Contact the New England Antique Radio Club. Their next swap meet is in about a week, in Brookline NH. Info at Http://nearc.net

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A collector of TV signal boosters and UHF converters -- God help me!
tv-boxes.com


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: May Mon 13, 2019 2:23 am 
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Location: Massachusets, 02019
I live in mass I could check the tube for you.


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: May Mon 20, 2019 1:27 am 
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Location: California
Wow, that is a really nice looking tv! I hope you can restore it and get it working again!

The thing is, if you can read schematics and have basic electronics knowledge, you CAN fix these antique tvs yourself. You just have to be patient. I fixed an Olympic tv from 1952 a couple of years ago. I had some experience restoring tube radios, but that was the first time I had ever tried to fix a tv. I was able to fix it and it's still working great! If I can do it, anyone can! :lol:

But yes, you definitely HAVE to replace the electrolytic capacitors before you even think about powering it up! Otherwise, you could end up burning resistors and making more work for yourself, or cause even more serious damage. You can replace them with modern electrolytic capacitors that are easily available in any electronics supply shop or online. You'll most likely have to replace all the paper capacitors too, but modern replacements are common, off-the-shelf parts.

- Chris


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Thu 26, 2019 11:20 pm 
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Joined: Apr Sat 27, 2019 7:12 pm
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Location: Attleboro, MA
Update on the TV "project"

I managed to get the chassis and picture tube out of the cabinet, and the tube tested ok.

I bought a tube tester. Which appears to not have been used in quite some time. I had to replace the cracking power cord. It does power on, and test tubes (tested some spare tubes from some spare radios). It appears to test them. But...well....the meter won't zero, needle is still left of the middle line when the calibration knob is turned all the way to the right. But, the needle does move into the good range when testing tubes. Testing for shorts seems to result in a faint glow on some of the tests that it shouldn't. I would think that perhaps I have shorting tubes, except I seem to consistently get this on at least 1 or 2 with every tube I test test. Although they aren't known good or bad tubes. But....just that I don't trust this tester, and am not sure how to service such things, so I'm stuck there as well, hence the need for a tube tester tester.

So, maybe at some point I'll be able to test tubes.

Went to this link to download schematics and diagrams:

https://www.radiomuseum.org/r/zenith_28t962r.html

Can only download 3 pages of the thing a day, so I'm still waiting until tomorrow to get the last 2 pages.

Was hoping for a simple list of all capacitors that correspond to the c numbers on the diagram and pictures of the chassis. No such luck. So I pulled up the first half of the schematic, zoomed it in on my laptop, brought up a spreadsheet on my desktop, and starting making a list.

Which is a challenge as some of the C numbers are blurry, but I figured, I'll double check things as I replace them, so long as I have a list of all the capacitors I need to get some sort of order together, I'll be fine.

Got to the 2nd half of the schematic, and....numbers started doubling up, but with different values. Brought the 2 schematics up on my screen side by side....they seem to be different halves of different schematics.

Uh...wha?

So.....looks like I don't have a schematic for this TV. I have 2 half schematics, maybe one half is to my tv. Not sure.

So yet another roadblock.

So far this project has been 1 step forward 2 steps back.

So....the current roadblocks:

A. Where do I find a full schematic for this?

B. How do I fix up a tube tester?

C. Once I have a list of capacitor values, where do I order capacitors, and what do I order?


Looks like there's no television Christmas for me anytime soon.....

https://www.youtube.com/watch?v=781I6b0WlZQ


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 12:13 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 369
Location: Elkhorn,Wisconsin,United States
Hi Jon,
If this is your first set you may want to get a copy of Sams folder 64-15. There are 20 pages in the folder. You can google it. Some of ARF members may even be selling schematics, check the ARF classifieds. Do you have any information about your tube tester ? You can create a new thread under the equipment heading.
Ed


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 12:19 am 
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Location: Dallas, TX
That radio Museum page has two sources of info, one is Sams the other is the Zenith manual.
Sams uses it own parts numbering system. If you ask a question here about a part be sure explain which source you are using.

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It's not the Destination, It's the Journey.


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 12:59 am 
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Location: Durham, NC
The service manual for that set is here: http://earlytelevision.org/pdf/zenith_2 ... manual.pdf
And the SAMS Photofact is at http://earlytelevision.org/pdf/zenith_8 ... _64-15.pdf
That should give you almost all you need to get started.
Have you tried contacting NEARC (now NEVEC) ? Most of its members are within an hour or two of Boston.

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Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
tv-boxes.com


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 1:26 am 
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Those sets are full of Black Beauty capacitors; they look like big, fat resistors, and will all be leaky. Some are in white cases. Also, watch out for the Micamold molded-paper capacitors.

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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 2:15 am 
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Joined: Apr Sat 27, 2019 7:12 pm
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Location: Attleboro, MA
Excellent links, thanks, I think I'm covered for documentation now.

The sams document has a nice list of 92 capacitors. Do I just go ahead and order the whole list? How do I best find all capacitors, any recommendations on what sites to use? Also, I notice the values are given in mfd for electrolytic and paper, mmfd for mica and ceramic, yet the listing doesn't specify the capacitor type, is there an easy way to determine which are which in the list? And also many of the capacitors in the list have no voltage rating, what's up with that?


Sorry if I'm asking a lot of newbie questions, but I really am completely lost and am likely to completely destroy this thing without a lot of help. I've barely managed to replace a few capacitors on other things in the past, that's the extent of my experience, I really do not know what I am doing at all, and am really struggling to get anywhere. All help is appreciated.


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 4:03 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Elkhorn,Wisconsin,United States
Hi Jon,
Using the Sams cap list;
Order C1 through C10. These are the electrolytic capacitors. Youl will see some with a sub notation letters like A, B, C , etc. These are all to be ordered as induvidual capacitors, they will be replacing those in the can capacitors.
Next order C35 through C92 inclusive, as long as they are listed with a voltage. Note you will not need C89 the 500pf 20kv cap most likely. These capacitors used to be paper, we use film type for replacement now days. You can make life easy for your self by ordering all the caps to be rated at 600 volts. Just noticed C85 is rated for 1000vdc, order at 1000volts then.
The electrolytic caps can be ordered with a higher working voltage. The listed capacitance may have to be ordered to next common modern value. I normally round up. For a 40 mfd @ 400vdc I would purchase a 47mfd @ 450vdc capacitor.
I think Just Radio's and Sal's will have what you require.
Ed


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 4:29 am 
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Joined: Apr Sat 27, 2019 7:12 pm
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Location: Attleboro, MA
Thanks, will work on getting that ordered now.

In the meantime, one of the cats has discovered a new place to explore...

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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 4:34 am 
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Joined: Apr Sat 27, 2019 7:12 pm
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Location: Attleboro, MA
Oh, I still don't know how to distinguish mfd from mmfd on that listing, as there is no designation on that list which is which.


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 4:34 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 369
Location: Elkhorn,Wisconsin,United States
Our family cats do the same thing. Every time I pull a chassis and leave the cabinet in the garage , they take turns using it for a bed . Really they use it for a hunting stand to chase down little critters. :twisted:


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 4:52 am 
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Location: Elkhorn,Wisconsin,United States
JonGatarz wrote:
Oh, I still don't know how to distinguish mfd from mmfd on that listing, as there is no designation on that list which is which.


The electrolytic caps are mfd , also known as uf. All the paper/ film are listed with a decimal point. for instance .005 is .005 mfd. The very small value capacitors are mmf or pf, they are usually in non-decimal form. For instance C52 is shown as 500. This is a 500mmf capacitor, it can be mica or ceramic, and is rated for 500vdc. You can replace mica caps with film caps in many cases. I wouldn't recommend replacement of ceramic and mica caps just yet, except maybe in the horizontal circuits.
I don't know if anybody mentioned, take good pictures of the wiring before you start to replace parts.
Ed


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 5:01 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5467
Location: Woodinville, WA USA
Jon, here are some articles that may help you get started.

Intro to TV restoration: https://antiqueradio.org/howfixtv.htm

Intro to restoring vintage electronics: https://antiqueradio.org/FirstStepsInRestoration.htm

How to identify and replace old capacitors: https://antiqueradio.org/recap.htm

Lastly, the following page lists over thirty vintage TV restoration case studies; none of them is identical to your set, but if you skim a couple, you'll see what's usually needed to get these old TVs working again:

https://antiqueradio.org/televisions.htm

Regards,

Phil Nelson
Phil's Old Radios
Phil's Old Radios https://antiqueradio.org/index.html


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 2:35 pm 
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I give you credit for taking on a TV chassis restoration. I've watched my long time repairman friend work on them and it seems to me that you have to truly know electronic theory to tackle the job. A recap is often just the start and then working the bugs out is where the men are separated from the boys! Good luck with the Zenith. It's one of the nicest of their porthole consoles.
Love the last pic by the way :) Now that's really a live TV version of "CATS".


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 5:13 pm 
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Location: Dallas, TX
Yes, do not be surprised that six months or more goes by before you are completely finished with the TV. You might get lucky and only need some capacitors and a few tubes being replaced. Often you come across problems with transformers, coils, pots and other parts. Adjustment is another aspect, one that may require more test equipment.
I would not replace mica or ceramic with film capacitors, the temperature behavior, stability and tolerance are different. Speaking of mica and ceramic capacitors, try not to replace any of those in the RF or IF sections. Those capacitors could effect the alignment because the new ones would not be exactly the same value of the original ones. Do not do anything to the coils in those areas either.
TV alignment takes special test equipment.

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Tim
It's not the Destination, It's the Journey.


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 Post subject: Re: Zenith porthole 1949 TV - 28T962R - restoration project?
PostPosted: Dec Fri 27, 2019 6:06 pm 
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Quote:
B. How do I fix up a tube tester?

Depends on the make and age. What tube testor do you have. Maybe a picture of the testor. Some testers like emissions testers can be fairly easy, but some conductance testers like the Hickok 600A are a nightmare of packed wiring, complex and endless transformer wiring, switches, and internal special vacuum tubes.
I searched the test equipment forum to see if you started a thread on your tube testor.

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