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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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18th Jan 2021, 7:38 pm | #1 |
Pentode
Join Date: Oct 2010
Location: London, UK.
Posts: 139
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TV22 frame blocking transformer.
Another my first telly...
Reading the other current my first telly thread on the TV22 has given me some useful pointers. Without it, I probably wouldn't have thought to check the frame blocking transformer for continuity. Lucky I did, or perhaps unlucky, depending on how you view things. The primary is open circuit. A little careful dismantling has proved the fault is deep within and not at the terminations, so it looks like a rewind job... It really doesn't look like a fun rewind, it's small, the wire is very fine, and the turns presumably number in the thousands. Of course the faulty primary is the winding closest to the core as well. Does anyone have details on the winding of these, it may save me counting a LOT of turns as I unwind it. I've measured the wire size at 0.07mm or 45 SWG, but I was using the world's cheapest nastiest micrometer, can anyone confirm the size?
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18th Jan 2021, 8:36 pm | #2 |
Heptode
Join Date: Feb 2006
Location: Roscommon, Ireland
Posts: 732
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Re: TV22 frame blocking transformer.
Hi Robin
The TV22 blocking transformer that I rewound had 2900 turns on the primary and 2000 on the secondary. 0.07mm wire was used for both primary and secondary. Frank
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18th Jan 2021, 8:43 pm | #3 |
Pentode
Join Date: Oct 2010
Location: London, UK.
Posts: 139
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Re: TV22 frame blocking transformer.
I'll get some 0.07 wire ordered then, thankyou!
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"Broken we can fix, cr*p is a design issue" |
19th Jan 2021, 10:01 am | #4 |
Dekatron
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
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Re: TV22 frame blocking transformer.
It seems to be a common problem to find an O/C blocking transformer on these sets, I reckon it is down to how the set has been stored. In a damp environment the windings get "green spot" corrosion.
The last TV22 I restored had this problem, luckily a forum member sent me a new bobbin at very reasonable cost. as there was no way I was going to rewind it! Mark |
19th Jan 2021, 1:44 pm | #5 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
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Re: TV22 frame blocking transformer.
Virtually any frame blocking transformer will work in these sets even if the "Resistance" of the windings is wildly different.
Also remember that if its an unknown type its possible it won't work first time as there are more than one way to connect it.
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19th Jan 2021, 8:46 pm | #6 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,173
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Re: TV22 frame blocking transformer.
Hi Folks, yes, a common job rewinding these transformers due to paper insulation being used with very fine wire that normally had poor enamel on it.
Skip the interlayer insulation and use grade 2 (double insulated) solderable enamelled wire and it will never fail again. They were designed to be 3000 turns to 2000 turns, but the set seems to work with a range of turns/ turns ratio as it is a tolerant circuit I normally wind these with 0.071mm wire Ed |