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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 30th Jan 2016, 2:25 pm   #21
Welsh Anorak
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Default Re: Dynatron CTV22A

The later ones (725 etc) used square silver buttons with separate tuning knobs. These weren't too bad - unlike the hybrid sets Pye seemed to improve the chassis as production went on - perhaps that's why the chassis numbering seemed to go backwards!
I think the 110 degree 22" (that had the German-sourced tuning knobs mentioned above) was the only delta-gun of that type used in UK sets. It seemed an unnecessary complication for an inch or two off the back.
You need to remove the IF strip and then heat and then gently ease all the ceramic capacitors up a little, then resolder both sides. Then solder the links. That should work, but is a bit of a tedious job. I used to fit the LEDCO panels back in the day. The picture was as good as a genuine IF board that worked properly - i.e. not very.
The power supplies did suffer from bounce, and it was never very easy to get them stable.
I have to admit I saw a 22" 725 in a poor state out in the rain last year - I drove on.
Glyn
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Old 30th Jan 2016, 2:54 pm   #22
Hybrid tellies
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Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
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Default Re: Dynatron CTV22A

I seem to remember problems with dry joints on the IF board causing horrible liney ringing pictures.
One to watch on these sets is the A1 supply capacitor which comes off the tripler. If this goes short circuit I have seen it take out the Tripler, LOPT, Line Output transistor as well as the PSU Thyristor before the fuse eventually blows.
Also I think it was the electrolytic capacitor across the 45v which is derived from the Line Output transistor emitter circuit would go open circuit causing some very strange visual effects on the picture.
Not the best of TV's, awkward to work on, poor reliability and even at best the pictures were only reasonable. Nothing to write home about but worth saving never the less.
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Old 30th Jan 2016, 5:08 pm   #23
FERNSEH
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Default Re: Dynatron CTV22A

Didn't the 731 series use the Mullard four chip decoder? TDA540, TDA990 etc.

DFWB.
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