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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 19th Jun 2016, 8:46 am   #21
Jac
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Default Re: Aurora problem

Thanks for posting your photos John.

My D16T (and B16T for that) have exactly the same sync "problem".
The black blocks on the beginning of the lines (not visible in the photos because the 16T receivers still have the 5:4 aspect ratio, and the output of the Aurora is 4:3) seem to influence the sync timing.

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Jac
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Old 19th Jun 2016, 9:29 am   #22
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Default Re: Aurora problem

Off the cuff, you have all looked at hum on the power supplies, but TVs being as they are with half wave supplies etc. it may be worth looking at what is on the neutral mains feed.
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Old 19th Jun 2016, 10:00 am   #23
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Default Re: Aurora problem

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Originally Posted by Boater Sam View Post
Off the cuff, you have all looked at hum on the power supplies, but TVs being as they are with half wave supplies etc. it may be worth looking at what is on the neutral mains feed.
A lot of the old TV-sets have double sided rectification, like in the annex for the Pye 16T receivers.

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Jac
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Old 19th Jun 2016, 11:41 am   #24
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Default Re: Aurora problem

Quote:
Originally Posted by Jac View Post
My D16T (and B16T for that) have exactly the same sync "problem".
The black blocks on the beginning of the lines (not visible in the photos because the 16T receivers still have the 5:4 aspect ratio, and the output of the Aurora is 4:3) seem to influence the sync timing.
Good Morning.
Jac I've been re-kindling my interest in TV over the last few weeks and have obtained some books and have been reading up.
I wonder if the issue you have is due to video content not being properly clipped out by the Synchronising separator? From what I have read this gives exactly the same effect as you have got.
This could be due to a leaky coupling capacitor or incorrect biassing of the valve allowing it to not be properly cut off allowing video content through, the black and white blocks could then spuriously trigger the line oscillator stage.

I think though this problem is different to the wavy issue mentioned earlier in the thread. On that note my friend had fed his set from a pure DC source and the effect completely disappears, which discounts any thoughts that the converter is the culprit.
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Old 19th Jun 2016, 1:09 pm   #25
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Default Re: Aurora problem

Hello D Cassidy,

Thank you for your comments.
Yes, that could very well be the cause.
It is not due to any faulty capacitor or incorrect biasing though.
All 16T receivers seem to have this.

Although it might be interesting to see it the design could be improved in this respect.
A nice future project.

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Jac
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Old 19th Jun 2016, 6:13 pm   #26
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Default Re: Aurora problem

I've been following this with interest. My Ferguson '45' portable suffers from a similar problem. I've literally replaced everything in the flywheel sync circuit but still not cured it (although improved from original}. Problem doesn't really notice on a picture but a testcard shows it.

Something I intend to investigate in more detail at some point.
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Old 19th Jun 2016, 6:23 pm   #27
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Default Re: Aurora problem

Sideband,

Could you post a picture of how it looks on the left side of the screen?

Is the effect dependent on the screen brightness (in other words: is it the same if the picture is turned a lot darker)?

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Old 19th Jun 2016, 8:09 pm   #28
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Default Re: Aurora problem

Here's a picture during the earlier stages of restoration. I'm not sure about brightness effect. I think it's the same but I'll try and check later and get a better picture.
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Old 19th Jun 2016, 8:36 pm   #29
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Default Re: Aurora problem

I think the brightness effect is just due to using a shutter speed faster than a 25th of a second.

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Old 19th Jun 2016, 11:31 pm   #30
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Default Re: Aurora problem

Peter. I'm not referring to the bright area across the screen, I'm referring to the post above mine where Jac was asking if the pulling is affected by the brightness setting
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Old 20th Jun 2016, 8:54 pm   #31
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Default Re: Aurora problem

Today I tried 2 different mains chokes because we thought the one I`d fitted was not up to the job but both of them failed to cure the problem.
I don't know what else we can try.

Robin
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Old 21st Jun 2016, 7:21 am   #32
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Default Re: Aurora problem

Is there perhaps a screened lead between video en sync separator?
I once had a set in which such a screened wire had a screen that was not properly grounded anymore (wire broken).

The cause certainly is not easy to find in your set!

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Old 21st Jun 2016, 12:56 pm   #33
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Default Re: Aurora problem

Were there ever any 405 line sets with flywheel sync? I know some DS had it, but did it work on 405?

Only asking as this would give a clue as to whether it is really a sync issue or possibly an image displacement in the line period.

However, are we being too fussy, how often did the average 405 line viewer sit there staring at a stationary test card? (Yes I know the music used to be entertaining).
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Old 21st Jun 2016, 1:30 pm   #34
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Default Re: Aurora problem

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Originally Posted by pichacker View Post
Were there ever any 405 line sets with flywheel sync?
Yes...lots of them. The first set I ever repaired (Ecko T283 from 1956) had flywheel sync. Used an EB91 as the flywheel diodes.
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Old 21st Jun 2016, 2:00 pm   #35
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Default Re: Aurora problem

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However, are we being too fussy, how often did the average 405 line viewer sit there staring at a stationary test card? (Yes I know the music used to be entertaining).
That question did float through my mind as well. In service the viewer would never have noticed this - probably just grateful for a piccy they could see without all light excluded from the room and locked in both the H and V.

Does no harm though to analysis the sets to this level - all part of the rich tapestry of the hobby.
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Old 22nd Jun 2016, 8:55 am   #36
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Default Re: Aurora problem

I never realised that flywheel sync had hit 405 so question is, do any of the sets displaying the picture displacement have flywheel sync?
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