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

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Old 26th Jan 2007, 6:47 pm   #21
Steve_P
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Default 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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Old 26th Jan 2007, 10:03 pm   #22
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Default 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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Old 26th Jan 2007, 10:53 pm   #23
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Default Re: Yet another TV22..... YAWN!

Quote:
Originally Posted by Sean Williams View Post
Right, have sussed the problem with the strange patterning - Is a DVD player issue.....

It looks like the LOPT has died - it was running fine, then pow - no raster, no EHT, and very feeble line whistle....

When I shut every thing off, the LOPT felt extremely hot.....
Sean. I'm glad you sussed the problem with the lines and patterns...it did seem like some sort of interference.

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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Old 26th Jan 2007, 11:12 pm   #24
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Default 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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Old 27th Jan 2007, 1:23 am   #25
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Default Re: Yet another TV22..... YAWN!

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I am also getting some variation on the resistance readings for the primaries.......
I wouldn't worry too much about variations in DC resistance unless perhaps they are way out. If the rest of the set runs without the overwind and the primary winding stays only slightly warm, it's probably OK.


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Old 28th Jan 2007, 11:58 am   #26
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Question Re: Yet another TV22..... YAWN!

Hi Sean,
did you read this? :
https://www.vintage-radio.net/forum/...hlight=tangens

Kind regards,
Darius
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Old 3rd Feb 2007, 12:28 am   #27
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Default Re: Yet another TV22..... YAWN!

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Originally Posted by Sean Williams View Post
However, disaster has struck!
It looks like the LOPT has died - It has always been a bit strange getting the EY51 to light correctly - it was running fine, then pow - no raster, no EHT, and very feeble line whistle....
I had a similar failure. From one moment to another a very quiet line whistle, a short moment only a vertical line and then no high voltage, no picture. At first I thought the lopt was burned. Of course it looked very bad... but a deeper view into the circuits revealed another source: There was a short in C34 (see schematics of Paul Stenning), the 470 pF capacitor which I had replaced before with a 630 voltage d.c. type. I have replaced it with the original cap which I have kept. Now I have high voltage and a raster again. But I have to fix the sync failure and the low line frequency.

Kind regards,
Eckhard
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Old 3rd Feb 2007, 11:12 pm   #28
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Default 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
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