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  #1  
Old 01-06-2018, 11:36 PM
Sealtest Sealtest is offline
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Zenith system 3 1979 repair help

Hello all, this is my first thread so I'll try to do my best describing what's going on with this Tv.

This particular Zenith came from a repair shop that shut down in 1998, so this thing unfortunately has been sitting for 20 years give or take. The first time on a variac it smoked, so I shut it off and looked around inside. Nothing was obviously damaged so I decided to put it back on the variac to poke around with a multimeter. Oddly enough the TV worked fine all of a sudden and has been running for maybe a month now, until today when it gave off an odd oder and the picture went wild.

After this I inspected the insides and saw nothing odd, just heat coming off (or seeming to come off) board 9-513. I put the tv back on the variac and now the screen will not fill up all the way unless the "zoom" feature is activated.

What do you all think the issue is with this? I have never done repair on TV's, just vintage audio gear and computers, so this is a bit different. My main concern is how to discharge all of the power from a TV to make it safe to work on.
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  #2  
Old 01-07-2018, 09:09 AM
zeno zeno is offline
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Sounds like you may have a 1st gen System 3 If so it will have
a big power transformer. It was the most reliable color Zenith
ever built & had a great pix.
In any case pull the HV board either a 9-160 or 9-154 ( IIRC ).
go over it for cold joints & check the hoz yoke plug for burning.
If no joy there we will need to know what chassis it is.
Good luck

73 Zeno
LFOD !
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Old 01-08-2018, 10:50 PM
Sealtest Sealtest is offline
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It has the power transformer if I recall correctly. Right now I have a friend who has zenith modules new in the box, so I may just be able to swap them. So far I haven't seen any burning on boards, but a cap has the top peeling off (though it does not appear expanded). These Zenith systems often have problems with the main filter caps so that may be what is going on.

The TV takes full voltage, but the picture is really wavy with a constant sweeping wave. The tube is also still not completely filling up. Hopefully these details help. I am trying to get a good idea of everything to do before clearing my bench for this massive thing.
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  #4  
Old 01-09-2018, 07:46 AM
zeno zeno is offline
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Sounds like the main filter cap is bad. They usually dont burn
though. If it has the power xformer there is an oil filled cap
in parallel with it. Its oval & just like a motor start cap.
When they short it kills the set. If it opens the pix will
pulsate. In any case be sure its not running hot when you are
done. A lot have been going lately. The 22-####-# is the part #

73 Zeno
LFOD !
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Old 01-09-2018, 05:46 PM
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Jon A. Jon A. is offline
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The cap's part number is 22-7126-01, TEDSS has them. They're a non-standard value and a dog to find elsewhere, can't use a 4uF cap to replace them.

https://www.tedss.com/22-7126-01
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Old 01-13-2018, 01:22 PM
Sealtest Sealtest is offline
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Thanks for the info on this! My tv does have a transformer so it has this part, but how do I know if it is the issue and not something else? Also I haven't gotten to the filter cap I see way back in there, but it looks like one that is made up internally of multiple caps. If that's how it is I should be able to build one for it.

Also, why can someone not just put in a normal 3.5uF cap in instead of the motor start type cap?
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Old 01-14-2018, 09:10 AM
zeno zeno is offline
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The cap is non polarized & the value is odd ball. Almost every Zenith
color built from 1974-1979 has one so common as hell.
Usually when they start going bad they get VERY hot. The value is
CRITICAL as it regulates the HV.
Yes main filter is multi section so no big deal.

73 Zeno
LFOD !
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Old 01-20-2018, 09:07 PM
Sealtest Sealtest is offline
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So I am looking at caps to rebuild the multisection and was wondering if the the 300UF cap if I could use this motor start cap. The original was polarized, but this one is not.

Will it work? Here is the link to it.

https://www.ebay.com/itm/Cylinder-30...19.m1438.l2649
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Old 01-21-2018, 08:54 AM
zeno zeno is offline
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No dont use that ! You probably wont find a 300 mfd so use
a 330 mfd. Voltage same or higher.
Maybe someone can pipe in as to the best place to buy caps is.

73 Zeno
LFOD !
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Old 01-21-2018, 02:28 PM
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Mouser/Allied/Digikey are all great online suppliers of NEW electronic components....Don't buy used or NOS when new is available.

Most lytics are 20% tolerance or higher. Tube be era lytics are typically -50/+100tolerance. The closest modern standard value usually will be fine.
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Old 01-21-2018, 08:27 PM
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I select high-reliability Nichicons whenever possible from Mouser. List of every one of their cap series here:

http://nichicon-us.com/english/produ...ini/index.html

Watch dimensions and lead spacing for through-hole applications. Leads for smaller caps may have to be formed for proper spacing. In many cases the holes are minimum 3.5mm apart but a cap with that lead pitch would take up too much room.
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Old 01-29-2018, 04:55 PM
Sealtest Sealtest is offline
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Thanks guys! I replaced the caps and have the tv running, but the results aren't great. The screen fills almost all the way up besides a black bar to the right. The small black bar would be easy to live with, but the picture still waves all over like waves on an ocean.


Looking around there are no obviously bad parts like bulging caps and burnt resistors, so I'm not sure where to go from here.

Fixing the black bar interests me the most at the moment since my trinitron has the same issue. Two birds with one stone seems like a good way to go. The wave sure is odd though, but at least this tv is showing some life and can take full voltage.
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  #13  
Old 01-29-2018, 06:58 PM
zeno zeno is offline
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Quote:
Originally Posted by Sealtest View Post
Thanks guys! I replaced the caps and have the tv running, but the results aren't great. The screen fills almost all the way up besides a black bar to the right. The small black bar would be easy to live with, but the picture still waves all over like waves on an ocean.


Looking around there are no obviously bad parts like bulging caps and burnt resistors, so I'm not sure where to go from here.

Fixing the black bar interests me the most at the moment since my trinitron has the same issue. Two birds with one stone seems like a good way to go. The wave sure is odd though, but at least this tv is showing some life and can take full voltage.
Hows about a screen shot or better yet a shot clip on U-tube ?
Still souns like filter can but "a picture..........".

73 Zeno
LFOD !
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Old 01-29-2018, 10:02 PM
Sealtest Sealtest is offline
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Making a youtube video was an excellent idea.


Here is the link to my video: https://youtu.be/ivY98nEe9Xs




I am still using the nintendo for testing, but before replacing the caps the same wave issue (though with a smaller screen), still happened.
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  #15  
Old 01-30-2018, 09:42 AM
zeno zeno is offline
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OK lets back up
Looks like an SK1961W or P
It is the power supply ( 99.5% ).
Did you change the 3.5mfd oval cap ?
Did you change the multi section filter can ?

Double check the values you used & the wiring.
Be sure the can caps are well grounded. ( all negative ends tied
to the metal can point )

Last possabilities are VERY remote that almost never happen
to any set.
Shorted choke.
Open or leaky rectifier.
If it uses an ON/OFF triac it could be that.

BTW Did you ever find what burned ???

73 Zeno
LFOD !
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