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 Post subject: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 4:37 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Knoxville TN
Hello, I have a Zenith 1950 Radio, Phono, TV combo. It is one of those monster cabinets that could house a safe.

The radio works, phongraph works. I tried my best to get the TV to work and after two techs looked at it they agreed the CRT is good, the voltages are good, except the seven point High voltage tranny is bad. What can I do with it?


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 1:52 pm 
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Location: Fernandina Beach, FL
I have experienced a similar situation. I was fortunate enough to find one on the auction site. However, if you advertise in the Classified section here, you may find one. They are out there and not terribly expensive (Like an RCA CT-100 HOT!). Several manufactures made them, Merit, Ram, Stancore etc.

I checked "the Auction Site" and saw a few there, not specifically what you are looking for though. Also, Moyer may have one.

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Don


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 2:00 pm 
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Update: Be careful if you buy a flyback on the auction site. I just looked at several and saw four that were advertised as NOS or NEW or NIB. They were obviously the old flyback that was removed from a TV set. Some showed evidence of arcing and many had wires with melted insulation where they had been disconnected. I am amazed that some of these sellers would have the nerve to sell them as new. But then, how naive can one be? :evil:

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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 2:32 pm 
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Location: Advance, NC USA
Is your Flyback Transformer mounted on top or under the chassis?
My 1950 Zenith porthole apparently had a flyback failure early in its life
and was replaced with a topside flyback. I have read posts that the
under chassis flybacks were problematic. I think the topside flyback is HOV-6.

BTW, have you measured the HV at the CRT anode?


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 2:42 pm 
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Joined: Jan Mon 28, 2013 9:35 pm
Posts: 784
Location: Santa Rosa, CA
If you can find the FLY number (Thordarson replacement) I'll
check my stash. Bought a big pile of NIB (yes, really) flybacks
from a TV shop ages ago. Long before old TV's became collectable.
Steve


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 3:53 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1521
Location: Lafayette, CO
If you want to try a FLY1, l have a few extras. Craig


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Thu 05, 2017 8:22 pm 
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zarco wrote:
If you can find the FLY number (Thordarson replacement) I'll
check my stash. Bought a big pile of NIB (yes, really) flybacks
from a TV shop ages ago. Long before old TV's became collectable.
Steve

analog.tv wrote:
If you want to try a FLY1, l have a few extras. Craig

Lots of good friends here! We work together...

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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Fri 06, 2017 1:33 am 
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Location: Detroit, MI USA
The Zenith flyback and any aftermarket replacements for it is becoming more and more difficult to get. They were a major problem when the sets were just a few years old and many sets that have turned up in recent years need a replacement.

Others have reported success in making a common RCA or Admiral flyback of the same vintage function in the Zenith chassis. Might be worth a try if nothing turns up.

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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: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Fri 06, 2017 2:30 am 
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Location: Redlands CA
I swapped a Fly1 RCA into a Zenith Mayflower, it worked great.

If the set uses the same tubes (6SN7, 6BG6, 6W4, 1B3) as the RCA in the sweep/high voltage section there's a good chance it'll work.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Fri 06, 2017 12:06 pm 
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Joined: May Sun 17, 2009 10:08 pm
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Location: Massachusets, 02019
Do you have the 12inch Zenith or the 16 inch version? The 12 has the fly under the chassis. The 16 and 19 has 2 different flys if it uses the 16Ep4 its under also. The 19Ap4 and 16Gp4 is on top.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Fri 06, 2017 4:19 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Knoxville TN
Thank you for the replies . It is an H series The Sams photofacts list: h2447r, h3267r and others. I think mine is h2447r,
The Zenith part number for Vert output is is 95-1240, hand written in beneath 1740. THe Horiz. output is s-17233. These are both listed under "Transformer Sweep Circuits" It is on the top of the chassis. The chassis has a number
on it 24h20. I tried to take a picture but the batteies died. It is the big console with radio and phono on the left. The phono is a Cobramatic. Underneath is ample storage for records. The TV is on the right, speaker underneath, The power supply sits on a ledge on the radio side. It is not protected behind the metal mesh back of tbe tv. The tube is 19 inches.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sat 07, 2017 2:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Detroit, MI USA
We are presuming that the TV chassis has already been completely recapped and resistors checked and replaced as needed?

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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: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sun 08, 2017 4:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Knoxville TN
Yes, It is ready, waiting and wiling to work. I spent weeks cleaning, replacing and checking components. The power supply is good.
The donut transformer inside the protective HV cage is bad. Or at least that is my understanding.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sun 08, 2017 5:16 am 
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Location: Redlands CA
jim campbell wrote:

The donut transformer inside the protective HV cage is bad. Or at least that is my understanding.


Does it looked fried? I know these Zeniths have a bad track record with the Flybacks but usually if one looks okay it most often is.

Are yours Techs familiar with Tube sets?

Sorry if it sounds like I'm interrogating, I just want to be sure you need a transformer, so often they get blamed when the problem is in the Oscillator circuit instead.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sun 08, 2017 4:54 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1239
Location: Knoxville TN
It looks fried. Or at least the rubber edging has fallen off. I don't use technicians so to speak- I had them give me an opinion (kind of like asking two doctors).
I did all the prerequisites before taking it to them. I would like to see it work . I really love the shape and size of the cathode ray tube.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sun 08, 2017 8:10 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Detroit, MI USA
They can look simply awful, with insulation cracking off, and still function perfectly. Likewise, I have had brand new ones out of the box which looked perfect and had never been installed previously, but they were defective and would not work in a set.

What does the drive waveform on the grid of the horizontal output tube look like on your scope? Can you post a photo of that waveform? Has anyone used a flyback checker to ring the windings and see if the transformer actually checks bad?

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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: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Mon 09, 2017 2:58 pm 
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Location: Pewaukee, WI
Mr. Detrola wrote:
They can look simply awful, with insulation cracking off, and still function perfectly. Likewise, I have had brand new ones out of the box which looked perfect and had never been installed previously, but they were defective and would not work in a set.

What does the drive waveform on the grid of the horizontal output tube look like on your scope? Can you post a photo of that waveform? Has anyone used a flyback checker to ring the windings and see if the transformer actually checks bad?


It is also important that the waveform be at the correct frequency. Too far off the correct frequency and you will loose HV.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Wed 11, 2017 1:33 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1239
Location: Knoxville TN
I appreciate the feedback. I have a 1949 RCA scope but have no idea how to use it. This Zenith is over my head. I have done
fairly good radio repairs over the last thirteen years but this project is kind of intimidating. The last time I tried to power it up-
all the tubes lite, the back socket of the cathode ray tube glowed filament orange but there was no picture on the porthole TV.

I was told I need to try and find a replacement transformer for the high voltage cage.


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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Wed 11, 2017 1:49 am 
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There is one test that you should be able to do if you have a voltmeter and a schematic diagram of the set. Connect the voltmeter to the grid of the horizontal output tube. Negative lead to the grid and the positive lead to ground. See if you get 20 volts or greater on the grid. If the voltage is there then the horizontal oscillator is running and the horizontal output transformer (flyback) may well be bad. If the voltage is not there then the oscillator is not running and you have to fix that before worrying about the transformer.

If you don't have the schematic, tell us the type number of the horizontal output tube and we can then tell you the pin number of the grid.

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 Post subject: Re: Made of unobtainium? Zenith porthole HV trans.
PostPosted: Oct Sat 14, 2017 12:21 am 
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Joined: May Sun 17, 2009 10:08 pm
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Location: Massachusets, 02019
I also have a 19 inch Zenith and also had to put a good used one in from a junker chassis. I was able to locate a new one for a spare in Georgia.


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