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 Post subject: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 12:29 am 
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i got this tv at an estate sale along with a pakard bell 19 inch color set with compactron tubes. this is a zenith 12 inch tube set. i got it and it had no power, i cleaned out all of the pots because it had been setting in a leaking barn for years and powered it on and it works good. nice sharp,bright CRT. the one problem i am having is the top of the picture goes all the way to the top of the screen but the bottom does not. is there a way to correct this? also in the photo, the picture looks kind of distorted in the middle, it is not actually like that that is just how the picture came out.


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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 1:53 am 
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There should be an adjustment called "Vertical Size" as well as one called " Vertical Linearity", they could interact some. Labeling could say V. Size or Vert. S, Vert. Lin. etc.
There could also be a centering control but on a color set you generally don't want to touch that one without having a pattern generator.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 2:34 am 
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i fixed the vertical. now it is slightly off art the sides, is this normal or can i fix this?

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 2:58 am 
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Look for an adjustment called width. How old is this TV? Depending on it's age, there may be parts that have deteriorated with age. If the picture changes size vertically when the set runs for awhile, then you definitely have parts that have deteriorated with age.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 3:05 am 
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i don't know. it is all tube, not compactrons. i think maybe the 60s. i fixed the height and it stays the same, the picture does not move. there are not any wax caps. now it just has a width problem and it does not change it stays the same. i dont see a width control.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 4:53 am 
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So it is new enough to not have any paper caps. Good. You may have a weak horizontal output tube, a weak damper tube or a weak rectifier tube (if it uses a tube rectifier). A tube tester might show the weak tube, but tube testers sometimes do not test these tubes correctly. Perhaps just use the set as is. It is not off by much.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 4:59 am 
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Some Zeniths of that vintage have a "width sleeve" on the neck of the CRT inside the yoke, if yours does you will see a possibly brownish fiber or aluminum or brass sleeve, maybe with a small collar on it visible where the area of the yoke clamp is on the rear cover of the yoke. You loosen the screw on the clamp and carefully slide the sleeve out of the yoke to increase the width.

You can see it clearly in this picture I found online:

https://www.boxcarcabin.com/zenith-12cb12zx-chassis.jpg

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 3:31 pm 
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The Zenith is apx a 1971. You can tell by the model or chassis number or
by date codes on major parts.
Your Packard Bell was probably built by GE about the same time. They were pretty junky
sets. Once in a while one will surprise you & run good.......

73 Zeno 8)
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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Tue 22, 2019 6:44 pm 
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ecaden1 wrote:
it is all tube, not compactrons.

Well, compactrons are tubes. They combine what would normally be several tubes into one glass
envelope. That usually means they have more than 9 pins.
Bottom line is if the adjustments can't fix a problem then a part needs to be replaced.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 12:46 am 
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the pakard bell set is ge i do believe, it has all ge branded compactrons. it is working okay as of now and i plan on keeping it because colour tube tabletops are hard to get around here. i am aware compatrons are tubes, what i was trying to say was it is an all tube set and the tubes in it are not compactrons

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 12:49 am 
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as far as the zenith, i have been using it for 3 days now and it has gradually got better. today i turned it on and it came right up into full screen. as far as capacitors they are mostly brown plastic ones and a couple ceramic caps which are wax caps inside. but as long as it works i am not going to replace them. the crt is not original i do not believe because it is a GE tube.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 3:04 pm 
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i had it plugged into a power strip with just a lamp and when i turn the lamp on the picture does that, and when it is off it just fine. so i don't know why that is. it is a 100 watt incandescent lamp. and that is all that is on the whole outlet. is there some sort of problem with the tv where it is not filtering something out or anything or is this normal. i have dealt with a couple of tube sets and none of them did this but they were not little portable sets, so maybe this is normal. i dont want to damage it by using it if something is wrong but it seems to work okay besides this.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 5:28 pm 
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Sounds like the power strip is dropping the voltage too far when the lamp is on. The TV seems more sensitive to this than others. I would check the power voltage at the strip with both the lamp and the TV on, the problem maybe in the power strip.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 9:46 pm 
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the strip and the outlet are 118 when lamp is of and 116 when lamp is on. it does it even when plugged into the same outlet when not on the strip.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Wed 23, 2019 10:25 pm 
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Location: Detroit, MI USA
The horizontal output or damper is probably very slightly weak, to the point that a 2 volt drop in line voltage (which will drop B+ by about that much) is enough to make it slightly narrow on the sides.

Nothing to worry about but try adjusting the width sleeve to make the picture full at the lowest line voltage it will be operated at. I wouldn't spend the price of a new tube if it's only a very slight space at each side.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Thu 24, 2019 6:28 am 
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Location: Belrose, NSW, Australia
That type of tube TV has no width stabilisation circuit, they relied instead on 10 or 20% overscan!

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Thu 24, 2019 12:22 pm 
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Mr. Detrola wrote:
The horizontal output or damper is probably very slightly weak, to the point that a 2 volt drop in line voltage (which will drop B+ by about that much) is enough to make it slightly narrow on the sides.

Nothing to worry about but try adjusting the width sleeve to make the picture full at the lowest line voltage it will be operated at. I wouldn't spend the price of a new tube if it's only a very slight space at each side.


+1, Adjust the width sleeve - you'll find it also affects linearity, so play with it a bit. Both the 12" and 16" models were that way.

On the 19" and 23" sets, the sleeve controlled linearity only (Zenith provided a separate width adjustment coil).

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Fri 25, 2019 2:45 pm 
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I have the same set, it was given to my parents for free when they purchased their new Zenith color TV around 1969-1970, mine still works perfectly. It was my set when I was growing up. Thanks for posting it. Happy memories.


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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Fri 25, 2019 6:06 pm 
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okay, thanks. it also seems kind of strange that a 100 watt lamp is lowering the voltage in my outlet that much. might want to check that and see if there is anything overloading the circuit.

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 Post subject: Re: zenith 12 inch tube tv
PostPosted: Jan Fri 25, 2019 7:47 pm 
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I wonder if your outlets are the type where the wires push into a hole instead of being wrapped around a screw. Those can make poor connection to the wire. If you have that type, the poor connection could be at a different outlet as the wiring is often chained through several outlets.

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