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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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26th Jan 2007, 6:47 pm | #21 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
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Re: Yet another TV22..... YAWN!
You can try a 941 LOPT - it looks the same, but if it works, then only as a temporary measure.
See if the original can be rewound. Mike Barker does them, so does Ed Dinning. Or see if Beery's got one... Cheers, Steve P
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26th Jan 2007, 10:03 pm | #22 |
Retired Dormant Member
Join Date: Jan 2007
Location: Westbury, Wiltshire, UK.
Posts: 2,451
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Re: Yet another TV22..... YAWN!
It sounds very much like flyback lines. IIRC the TV22 doesn't have any flyback blanking? The trick is to adjust the brightness until they JUST go. Long time since I had my TV22 running.
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26th Jan 2007, 10:53 pm | #23 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,567
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Re: Yet another TV22..... YAWN!
Quote:
Re the transformer it may just be the EHT overwind. If it's possible to remove the overwind you could try the set without it. If the rest of the set works OK, then it may be possible to use an overwind from something else. I've done it before when I repaired a KB New Queen LOPT with a KB Royal Star overwind! It was a tight fit but I had good pictures. Rich.
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26th Jan 2007, 11:12 pm | #24 |
Dekatron
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Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
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Re: Yet another TV22..... YAWN!
Ok, I have done a sort of Post Mortem on the lopt - indeed the EHT overwind is shot - I am also getting some variation on the resistance readings for the primaries.......
This part of the set has always been a bit flaky! I think the spare Fergie transformer gets tried next week........ Cheers Sean
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27th Jan 2007, 1:23 am | #25 | |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
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Re: Yet another TV22..... YAWN!
Quote:
Rich.
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28th Jan 2007, 11:58 am | #26 |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: Yet another TV22..... YAWN!
Hi Sean,
did you read this? : https://www.vintage-radio.net/forum/...hlight=tangens Kind regards, Darius |
3rd Feb 2007, 12:28 am | #27 | |
Retired Dormant Member
Join Date: Mar 2005
Location: Braunschweig, Germany
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Re: Yet another TV22..... YAWN!
Quote:
Kind regards, Eckhard |
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3rd Feb 2007, 11:12 pm | #28 |
Retired Dormant Member
Join Date: Mar 2005
Location: Braunschweig, Germany
Posts: 208
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Re: Yet another TV22..... YAWN!
Hello,
my last posting needs some more explanation. The failure looked at first glance like a dead lopt. And when I opened the high voltage cage I found the lopt looked really bad with tar flowing down the core: http://bs.cyty.com/menschen/e-etzold...eilentrafo.JPG But I didn't gave up. In the posting https://www.vintage-radio.net/forum/...9&postcount=16 Darius gave an instruction how to measure the resonance frequency of the lopt. He found 38 KHz with 1 Vpp (good lopt). I found 110 KHz with 0.3 Vpp and 230 KHz also with 0.3 Vpp. In the expected range around 38 KHz there was nothing. This was suspect. Darius' next hint was to test C34. This is the small flat capacitor at the lopt (T2 over d and e). Some more informations about this failure might be interesting for those which have recapped the main deck. I have replaced all capacitors with 630 Volts d.c. types. Darius gave me the hint that the flat capacitors are not waxies. They are covered with wax, but inside they consist of mica. I replaced C34 with the original one. The "new" capacitor had indeed a short. After replacing the capacitor I measured the resonance frequency again. Now I found a peak at 40 KHz with appr. 2 Vpp. This might be OK. Now it was the time to switch on the set: http://bs.cyty.com/menschen/e-etzold...irstLight4.jpg To prevent overheating of the lopt I have inserted an R/C combination at the screen grid of the PL38 like Darius has recommended in: https://www.vintage-radio.net/forum/...328&page=7#135 https://www.vintage-radio.net/forum/...7&d=1106646370 The remaining failures in the set are no synchronisation and line frequency below threshold. I will do the sync next. Kind regards, Eckhard |