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Old 24th Sep 2016, 4:05 pm   #41
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Default Re: When did synchronization to the mains end?

I have seen one of the racks from the converter in my bosses office at PYE TVT in 1980 which contained a load of multi sided glass delay lines about a foot or so in diameter and half an inch thick. In the end they stored a whole picture (I think it was two half frames) with loads of taps to get the right line for output. Luckily the line frequency was/is almost the same simplifying it a bit, no need to change the line length the difference was just ignored.

As far as I can remember it worked by filling the delay lines with the 525/60 video and then selecting 625 lines from the storage at 50Hz. I don't know if some line pairs where averaged though or if the output was asyncronous to the output or the BBC synced to them.

These are 36 year old memories and are fogged with time, I would love to find a paper about it.
 
Old 27th Sep 2016, 3:27 pm   #42
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Default Re: When did synchronization to the mains end?

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Originally Posted by Nicklyons2 View Post
In practice, even as late as the 1970s some SPGs had a mains lock position (as well as Xtal & 'genlock'). I was thinking mainly of the early years of TV OBs and I think you'll find most, though I can't guarantee all, were from locations in and around London where it wouldn't have been too difficult to persuade the LEB to provide a supply from the nearest feeder pillar.
Yes you're correct, I remember some of the Aston SPG's having a 'mains- lock position.
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Old 27th Sep 2016, 3:32 pm   #43
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Default Re: When did synchronization to the mains end?

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Originally Posted by merlinmaxwell View Post
As far as I can remember it worked by filling the glass delay lines with the 525/60 video and then selecting 625 lines from the storage at 50Hz. I don't know if some line pairs where averaged though or if the output was asyncronous to the output or the BBC synced to them.
So that's how they did it, storage by glass delay lines.
No digital storage then?

DFWB.
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Old 27th Sep 2016, 6:11 pm   #44
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Default Re: When did synchronization to the mains end?

Yes, glass delay-lines were at the time seriously 'leading-edge' technology - both in analog-TV signal-processing and in various digital-computer applications [such as buffering the delivery-of-data to/from high-speed hard-disks on some early/mid-1960s computers].

The development of glass delay-lines in time provided the necessary 'storage' to make PAL colour-TV a practical, consumer-priced possibility.

[sidenote: in the 1980s a military two-way radio I was involved with used a specialist glass delay-line of around 25 Milliseconds to delay the signal down the audio-chain and so avoid the brief burst of "sharsh" between the end-of-transmission and the squelch closing the audio-channel. This was thought revolutionary at the time!]
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Old 27th Sep 2016, 7:45 pm   #45
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Default Re: When did synchronization to the mains end?

Did other countries broadcasters lock their monochrome TV systems to the mains? How did optical standards converters cope with out of sync systems without weird effects?
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Old 27th Sep 2016, 7:57 pm   #46
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Default Re: When did synchronization to the mains end?

With regards to optical standards conversion of 60Hz to 50Hz systems I do remember that the 10Hz rate moving dark bar was removed by a clever video AGC system. The bar was tracked by the AGC.

I'm sure other early TV systems employed mains sync.

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Old 27th Sep 2016, 8:03 pm   #47
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Default Re: When did synchronization to the mains end?

I don't think that they did: I can remember noting, when watching our ancient telly in about 1963 with the frame locked to the mains that when a broadcast from Eurovision came on the air that the picture started "breathing" as the mains was no longer locked. Synchronism was restored as soon as the broadcast ended.

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Old 27th Sep 2016, 8:36 pm   #48
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Default Re: When did synchronization to the mains end?

That's right, for receiving Eurovision our end of the receiving chain we would have to go off mains lock. In 1963 it's likely BBC was still using an optical converter. As all the Continental TV systems are also 50Hz field rate the converted 405 picture would been gen locked to input standard field rate. No moving bar.

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Old 27th Sep 2016, 10:46 pm   #49
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Default Re: When did synchronization to the mains end?

Wow that's something I never thought of, 50fields per second abroad when their mains was 60Hz. The field rate couldn't be far away from the film-industry 24fps else telecine would be a nightmare...

So on the continent, the frame frequency would never have been lockable to the 60Hz mains then? What about comparatively fast-moving Humber or 'breathing', or was it just not a problem?
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Old 28th Sep 2016, 1:46 am   #50
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Default Re: When did synchronization to the mains end?

Continental mains is 50 Hz, same as the UK (although what we import comes in as DC, and then we invert it back to 50 Hz). It's mostly just North America and part of Japan that use 60 Hz.
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Old 28th Sep 2016, 2:50 pm   #51
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Default Re: When did synchronization to the mains end?

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It's mostly just North America and part of Japan that use 60 Hz.
And yet the part of Japan which uses 50Hz has no problem in viewing a TV system which operates at 60Hz.
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Old 28th Sep 2016, 4:27 pm   #52
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Default Re: When did synchronization to the mains end?

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Wow that's something I never thought of, 50fields per second abroad when their mains was 60Hz. The field rate couldn't be far away from the film-industry 24fps else telecine would be a nightmare...
Well in the USA that's exactly the 'problem' they had with telecine machines. They got around it by using a 3:2 pull down technique. Plenty of info on the www describing the system in greater detail - just enter "ntsc telecine pull down" into your favourite search engine.

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Old 28th Sep 2016, 4:36 pm   #53
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Default Re: When did synchronization to the mains end?

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Originally Posted by FERNSEH View Post
With regards to optical standards conversion of 60Hz to 50Hz systems I do remember that the 10Hz rate moving dark bar was removed by a clever video AGC system. The bar was tracked by the AGC.
ATV had a Bosch optical converter at Elstree, this link gives some interesting insight to the AGC system you mention:

https://books.google.co.uk/books?id=...verter&f=false
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Old 29th Sep 2016, 8:40 am   #54
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Default Re: When did synchronization to the mains end?

From 1978 to 1982 I was chief engineer at a TV facilities house in Germany and we had a Bosch Fernseh optical standards converter. I, with a little help from an engineer from ZDF, had the task of keeping it in spec. It was very reliable but when there was a problem, it was never simple and we had many hours of "fun" getting it going and tweaking the myriad of adjustments hidden in the very deep plug-in modules in the 21" DIN racks. When lined up properly, The system was capable of very good quality conversions with none of the digital artifacts that are always seen on modern program material.
For those of you who have not seen a Bosch-Fernseh module of that time, they were beautifully made with most of them having small PCBs mounted along the two sides. Access to the component side of the PCB was given by mounting the PCB on a hinge with a slip-ring for external connections. To my mind, they were a real work of art and gave little trouble.
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Old 13th Oct 2016, 2:26 pm   #55
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Default Re: When did synchronization to the mains end?

Ooh I remember those Bosch-Fernseh gizmos, my only encounter being in the early years of electronic TV titling. The norm was to use 'Letraset' or similar for title sequences sometimes on a bus destination roller until some enterprising US manufacturer came up with an electronic caption generator, (Chyron if memory serves), but it was only available in a 525/60 version so its output was converted before it could be keyed in to the 625/50 picture. The physical amount of gear to obviate the need for someone to rub down a few letters of Letraset was remarkable! Much fun could be had getting crude 'scroll' and 'crawl' effects by mucking about with the standards convertor's genlock sync train.
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Old 13th Oct 2016, 4:19 pm   #56
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Default Re: When did synchronization to the mains end?

Ampex used to handle Chyron internationally and I used to be the product manager. A super bit of kit and the word Chyron became almost generic in the US, it being used like Hoover is used here!
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Old 13th Oct 2016, 6:04 pm   #57
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Default Re: When did synchronization to the mains end?

It was fairly common here in the U.K. too.

I used to install both For-A and Chyron character generators.

Happy days, real engineering!

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Old 13th Oct 2016, 6:14 pm   #58
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Default Re: When did synchronization to the mains end?

I seem to remember that, at the time of year when foreign interference was experienced on UHF TV, we could sometimes get the video of French stations ( in black and white) superposed on a Uk channel, but that the French video was not always synchronised to the UK video.

Regarding telecine, the 6th edition of the ITT Reference Data for Radio Engineers has info on the contemporaneous (1970's) USA TV/Video practice. It mentions that telecine used a projector running at 24 fps (frames/sec), but arranged to give 120 flickers/sec (evidently by fitting a 5-bladed shutter). A normal sound film projector runs at 24 fps and has a 2-bladed shutter to give 48 flickers/sec, silent projectors have 3 bladed shutters to also give 48 flickers/sec at 16 fps). For PAL systems, telecine projectors could use a 2-bladed shutter by running at 25fps to get 50 flickers/sec, resulting in a 4% increase in speed and consequential shortening of the run time relative to a cinema screening.

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Old 16th Oct 2016, 9:27 am   #59
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Default Re: When did synchronization to the mains end?

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Ampex used to handle Chyron internationally and I used to be the product manager. A super bit of kit and the word Chyron became almost generic in the US, it being used like Hoover is used here!
I'm am so sorry to 'rain on your parade', we had the rather dubious pleasure of having to maintain two of these at LNN/GMTV, I think they had the Max! and Maxine. Perhaps you were involved in the supply of them?

I'm afraid they were universally hated by the people who had to operate them and by the people who had to maintain them. I think the reason GMTV bought them was because they were the only bits of kit around at the time that interfaced directly to the Newstar computer system. Then Aston came along and the rest is sort of history.

I readily accept however your comments that this kit was extremely popular around the world and was the de-facto market leader. We nicknamed it all 'Cry -on' as it could reduce you to tears if it went wrong. Sorry about that.

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It was fairly common here in the U.K. too.
My first experience of this kind of broadcast kit was the Riley 'Capgen' - late 70's/early 80's. It had some PCB veroboards where you could solder diodes across tracks to get custom made characters. I always thought it was very sophisticated at the time. (BFBS television used one to get their on-air symbol - sort of orangey thingy, probably on the www somewhere).
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Old 17th Oct 2016, 11:09 am   #60
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Default Re: When did synchronization to the mains end?

As to ease of use, it really is down to what one gets used to. I found the Astons terribly non-intuitive to operate, a bit like Windows with needing to hit the start button to turn off!!
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