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 Post subject: Predicta Yoke part numbers/specifications
PostPosted: Sep Sun 13, 2020 10:53 pm 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 30
Hello folks.
I'm working on a 10L43 chassis Predicta (17 inch). I've replaced all the usual culprits in the vertical circuit but one issue remains. The top of the raster is compressed. V-LIN and Height can be twiddled until an apparent compromise can be reached with a linearity test pattern, but actual video is obviously not "right". I don't think it is the yoke, actually. There is no keystone issue or ringing. But I would like to rule out the yoke so I can bang my head on the vertical circuit some more. The TV yoke part number is 75-10508-6. But both Sams and Rider lists it as a dash 14. I would really appreciate a pointer to a cross-reference of some kind that gives me inductance/DC resistance and so on for Philco Predicta yokes. I have a dash 24 from a 21 inch predicta that I pulled out of service because of vertical ringing. It was from the Danish Modern 21 inch model. It behaves the same way in this current chassis and the vertical compression is evident too. Would love to know what a dash 24 is, though.
Pointers appreciated!


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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Sep Thu 17, 2020 6:48 pm 
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Location: 07450, New Jersey
The Danish Modern (Continental) yoke should be a match for the 10L43 chassis however, the -24 does not show up in any reference that I have. According to the Thordarson catalog, the -6 is for the Tandem and would not be the correct yoke. The inductance for the proper yoke is listed in the Sams parts list (24mh Horiz and 37mh Vert) and the resistances are on the schematic. The Thordarson Catalog lists the following yokes as being compatible with 10L43: -14. -13, -16, -22.

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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Sep Fri 18, 2020 12:04 am 
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Joined: May Sun 07, 2017 11:35 am
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Location: Belrose, NSW, Australia
It's not the yoke.

Does the image start compressing in an area about 1/3 way down the screen as you increase the height?

If as you say you have replaced everything else (I assume that includes the bypass caps), and you have this kind of linearity issue, you might have a shorted turn in the vertical OP transformer. This was reasonably common in the days before polyester insulated winding wire.

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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Sep Fri 18, 2020 11:47 am 
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Joined: May Sun 17, 2009 10:08 pm
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Location: Massachusets, 02019
Predicta yokes not a common problem.


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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Sep Fri 18, 2020 11:56 pm 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 30
Thanks to ALL the folks responding to this. A couple of interesting things about working on antiques is that you must return to your basic electronics skills AND you have to develop your detective skills. This thread started with my work on a Predicta Princess that had the symptom I described as well as a raster that became progressively brighter at screen right. After posting my original, I set forth to eliminate the raster issue and soon discovered that yoke lead dress affected things. It was then that I realized that indeed, I had the wrong yoke in it.

Putting the right yoke in it fixed the weird raster brightness issue, and seemed to improve the top linearity. (That might be wishful thinking).

Lead dress can be important, but the major way it affected a video issue with this TV was the thing I noted that sent me in the right direction.

Further comments of antique finding interest:

The -24 yoke came to me in a Continental that I drove half way across the US to pick up off ebay years ago. I knew it was not working when I bought it, and I planned to (and did) fix it up pretty well. The yoke was ringing once I got it up and running. All horizontal lines rang with a sine wave distortion starting at screen left and continuing out about 3 inches on the screen. I stole a yoke out of the above mentioned Princess...extended the leads...and FORGOT about it. (I am guilty of putting the wrong yoke in the Princess, in other words).

The -24 yoke probably came out of some other Philco. On further inspection, it has the wrong centering magnets on it. I suspect the chap I purchased this from saw me coming from miles away.
So caveat emptor when shopping for an antique.

See my attached pic of the yoke, and if you have a dash 14 lying around anywhere, please let me know!


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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Sep Sat 19, 2020 12:01 am 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 30
One other note I forgot. The chassis in the Continental is a 10L43A. Maybe this refers to the extra asbestos between the HV cage and the H output tube. I was thinking there might have been a dash 24 yoke associated with a 10L43A.


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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Oct Sat 10, 2020 11:05 pm 
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Joined: Aug Sun 11, 2019 5:45 am
Posts: 30
Just a brief follow-up to the 10L43/10L43A chassis and -24 yoke.
On closer inspection of the 10L43A chassis, I can assume that it is a late version for the Continental. The asbestos-and-metallic heat shield is affixed to the side of the HV cage, presumably to deal with the heat blasting off the H output tube radiating upward to the cage and melting the flyback. But I have also taken note that the horizontal oscillator tube socket is shielded, with the shield being manufactured on to the socket. The type that you turn a half turn and push downward on. Further, there is a terminal board located next to the V output transformer that places an R-C network of a 6.8K and a .01 disc into the line going to the CRT interface socket. I just thought I'd share that with you folks. Still looking for a -14 yoke. I'll post a request elsewhere on this forum.


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 Post subject: Re: Predicta Yoke part numbers/specifications
PostPosted: Oct Wed 21, 2020 8:25 pm 
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Location: Waxahachie Texas
Check your pm.

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