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 Post subject: zenith tv
PostPosted: Mar Thu 08, 2018 3:26 pm 
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Joined: Jan Wed 17, 2018 8:17 pm
Posts: 57
yes... i have an old zzenith tv i got on craigslist for 20$... it is like the one in the picture. when i turn it on the tubes all light up and once it warms up there is a humming sound. it is very loud and with the volume all the way down it is real loud, sounds like the filter hum if it were a radio, when it is all the way down it is loud and when you turn up the volume it quiets down. when you change the channel it makes a bit of a noise but no static. nothing on the crt. i do not have a tube tester or a crt tester so i can not tell that. what would be the first step on trying to get it working. (i do not want to restore it just do as little as possible to get it working)


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 4:18 pm 
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Location: Detroit, MI USA
You can't do as little as possible to get it working on a TV of that vintage, at the minimum it's going to need all the electrolytic and paper caps replaced. Just applying power to it could cause damage, depending upon the failure mode of whatever is causing it not to work.

Before doing anything you need to find someone in your area that will either test the CRT for you, or loan you a CRT tester. Since they are no longer rebuilding CRT's and used good ones can get expensive, you would need to be 100% certain yours is good enough to use before spending money on doing other repairs. You would also need to test all the other tubes in the set to determine if any of them are bad.

Back in the day when tube type TV's were fairly new and still in daily use, the chances were that if something went wrong, at least 50-60% of the time you could fix it by replacing a tube or two. Today, that's highly unlikely on an unrestored set, and the tubes are often found to be among the more reliable things in the set.

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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 5:19 pm 
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Joined: Aug Thu 20, 2015 3:09 pm
Posts: 726
Location: Albion, CA, USA
Nice TV! Don't plug it in again. As stated above you could do serious or even fatal damage to it. Either decide to go through it yourself or sell it to someone who will. Or perhaps you could pay someone to do the work. Where do you live?


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 5:25 pm 
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Joined: Jan Wed 17, 2018 8:17 pm
Posts: 57
oh, yeah i forgot i did bring it up on a variac and measured the watts it was taking. so i was not going to blow it up.


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 5:29 pm 
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Joined: Jan Wed 17, 2018 8:17 pm
Posts: 57
i am in north carolina, can not pay anybidy alot, i am 15 years old. i collect and repair old radios. i dont restore i just repair. i also have a little blue ge tv that is mostly compactron and it does not have sound or picture but tubes light up, i know crt in it is good beause it used to work but i did something and it quit. i will put another post about it as well and maybe i should focas on it before the zenith because it looks like it is going to be alot to get going.

also dont worry i have a variac and watt meter and was slowly bringing it up while keeping an eye on the watts taken just like i would with a vintage radio


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 5:49 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 753
Location: Dallas, TX
ecaden1 wrote:
i am in north carolina, can not pay anybidy alot, i am 15 years old. i collect and repair old radios. i dont restore i just repair. i also have a little blue ge tv that is mostly compactron and it does not have sound or picture but tubes light up, i know crt in it is good beause it used to work but i did something and it quit. i will put another post about it as well and maybe i should focas on it before the zenith because it looks like it is going to be alot to get going.

also dont worry i have a variac and watt meter and was slowly bringing it up while keeping an eye on the watts taken just like i would with a vintage radio

Always good to have some new blood in this activity. I would guess this TV is from the mid 50's.
I agree with Mr. Detrola completely. A tv is many times more complex that a typical radio, there are a lot of capacitors of the size that need replacing. By the time you "repair" a set this old you may have as well done a full electrical restore. They are also much more dangerous.
One problem with your technique of the use of the variac and wattmeter is that a working TV can draw well over 100 Watts, but if that 100 W is being drawn by one part in a defective TV then that part burns up.
You realize that currently there are practically no TV broadcasts that you can receive on the old analog sets. The best you can hope for is a blank white screen with no sound. You will have to attach a DVD player or similar to get a picture.

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


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 6:07 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 26440
Location: Detroit, MI USA
By the time I was 15 I had already been working on this stuff for several years, and worked every day after school in a TV shop. You can certainly learn using the sets you have.

That GE should be a good set to learn on if you take things slowly because it's just enough newer than the Zenith where it might not need a major overhaul to get it going again. Start a discussion on the GE, and you will find people that have suggestions what to try.

The main thing everyone is trying to point out is that TV's are quite a bit more complicated than radios and sets as old as the Zenith will need a lot more done to them to make them work well enough to watch anything.

Let's see if we can find someone nearby with a CRT tester, and once you have determined the condition of the CRT you can set the Zenith aside until you gain experience on the GE, and then go from there.

What city in NC are you in?

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 6:32 pm 
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Joined: Jan Sat 16, 2016 10:03 pm
Posts: 351
It's the same as buying a 60 year old car that has been stored in a barn for 50 years. You may get lucky and the get that old car running with minimal effort, but its not going last long!!!!!!!


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 08, 2018 11:42 pm 
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Joined: May Sun 07, 2017 11:35 am
Posts: 281
If you've worked on radios you could test the CRT this way:

viewtopic.php?f=3&t=331576

Read the typical test results on the last page of the post.

I concur, old TVs need a LOT more work than old radios. Everything in the TV needs to be up to scratch to get a watchable result, unlike a radio that will work with many tubes at 30%.

The last little intermittent faults take the most time.

But it's rewarding!


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 Post subject: Re: zenith tv
PostPosted: Mar Fri 09, 2018 12:04 am 
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Joined: Aug Thu 12, 2010 6:25 pm
Posts: 168
Location: Durham, NC
Ah, the enthusiasm and innocence of youth! Good for you.

I'm in Durham NC, and while nowhere near as experienced in TV servicing and restoration as many on this board, I'm willing to help if I can and am somewhere near you. I have a tube and a CRT tester, etc.

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Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
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 Post subject: Re: zenith tv
PostPosted: Mar Fri 09, 2018 1:03 am 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 753
Location: Dallas, TX
Actually I was about 15 when I started tinkering with radios and TVs. I vividly remember accidentally discharging a filter cap using my thumb while working on a AA5 that I had recently unplugged. Ha-ha!

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


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 Post subject: Re: zenith tv
PostPosted: Mar Fri 09, 2018 3:01 am 
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Joined: May Sun 07, 2017 11:35 am
Posts: 281
Yes, the old car analogy is a good one.

It's usually not too hard to get an old TV running, but then the little faults start showing up, one after another. Even if you've re-capped it.

I have a chassis on the bench at present that must set some kind of record for this. It was running weeks ago, but the subsequent faults (mainly intermittents) now number about 35 or so. At least one new fault every day!


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 Post subject: Re: zenith tv
PostPosted: Mar Thu 15, 2018 7:09 pm 
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Joined: Jan Wed 17, 2018 8:17 pm
Posts: 57
yes i know i have the equiptment to hook it up to a signal, as for all of the other. i bought the tube for the ge and it turns on no hv or sound but all bulbs glow, like i say the crt is good because it did work


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 Post subject: Re: zenith tv
PostPosted: Mar Tue 20, 2018 2:14 am 
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Joined: Jun Thu 25, 2015 3:21 am
Posts: 1239
re your ge
if all tubes light but no sound no light on picture tube you have a problem in the low voltage power supply. test the rectifier tube and check out any resistors condensers or chokes in the low voltage supply. you probably have no voltage in the low voltage supply.

re zenith again hum is a problem in the low voltage supply.

no light on crt could be either a problem in the low voltage supply or a problem in the high voltage supply. since you get some sound the most likely problem is low or now high voltage.

unlike many here i am not an advocate of the change all paper condensers or electrolytic condensers in the set. test every component in the section you are having trouble with and replace the ones that are bad. the parts within tollerance can be left alone.

you are correct to test all tubes first and replace any weak or bad ones.

in my experience there is no problem powering up a set to get a baseline on what its operating condition is. of course you need to use a variac and monitor current while doing this. any sign of excessive current draw and power down imediately.

you will need test equiptment to service vacuum tube tvs.

at a minimum you will need.

a tube tester
a vtvm with high voltage and rf probe as well as the normal ac and dc probe
a condenser tester. yes even new condensers should be tested before installing
there are other pieces of test gear that really help with troubleshooting a tv. i wouldnt try it without my television analyst. this really speads up troubleshooting. it will substitute any signal in a tv so you can use signal injection to locate the faulty stage easily.

if you need to do an alignment on the tv you will need a sweep generator a marker generator and an osciloscope.

there are many good books written when these sets were new on correct troubleshooting tecniques. i recomend you read as much as you can.

good luck and welcome to the rewarding world of servicing vacuum tube electronics.


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 Post subject: Re: zenith tv
PostPosted: Mar Sun 25, 2018 1:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 7781
Location: Beaver Falls, PA. USA
Welcome! TV service equipment is plentiful at hamfests and swap meets, and there were some good repair courses and books in the old days which also turn up as well.

Some of us have extensive TV repair experience, so don't hesitate to ask questions.

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Tim KA3JRT


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 Post subject: Re: zenith tv
PostPosted: Mar Sun 25, 2018 5:28 pm 
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Joined: May Thu 14, 2015 4:15 pm
Posts: 753
Location: Dallas, TX
ecaden1
you will find different opinions on any forum sometimes.
I wouldn't be discouraged about the amount of equipment you might need. If you get a vintage piece of test equipment you probably will need to fix it up first. My list of equipment for a beginner would be the following.

VTVM or DVM, RF probe is useful, you might get by without a HV probe.

Oscilloscope, back before the mid 60's a 5 Mhz scope was enough, but I would go with at least a 10MHz and the horizontal sweep should be the triggered type. Old scopes used a oscillator that needed to be synced to the input signal. 10X and 1X probe or one that converts between the two. You can make a RF probe or find one.

Either a Signal Injector or a RF generator and a Audio generator. Signal Injectors aren't commonly manufactured today, they output a audio frequency that also contains RF frequencies. You can find info on building one online they are simple.

Tube Tester, could have a set of good substitute tubes instead but since a TV has many tubes the tester might make more sense. It doesn't have to be fancy, even the most expensive can't catch every problem.

Dim bulb tester or variac with ammeter.
Isolation transformer if TV doesn't have a power transformer.
Sometimes very simple things like a bad compact fluorescent bulb can be useful.
I wouldn't plan on doing things like alignment until much latter.

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


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