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Thorn 2000 CTV: Worlds First all Transistor Colour Television: The prototype

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crustytv
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I'm sure we are all well aware of the remarkable Thorn 2000 series colour television and just how ground breaking it was for 1967. Equally most are aware of the chassis and how it looks in its two forms, 19" and 25", What I had not seen until today was the 2000 prototype.

Whilst spending an enjoyable morning with an ex TV engineer, he grabbed his copy of The Setmakers: History of the Radio and Television Industry, I had not seen this book until today. Immediately flipping through to the section that floats my boat, namely the advent of colour. I was amazed to see the 2000 prototype on the Thorn designer engineers bench, all lashed up in true "Jim Williams" style.

2kproto1.jpg

I have heard of a mythic Thorn 1000 being mentioned by folk here and elsewhere, that it was mainly valve. Whether this was ever built of is just an urban legend, I guess we will never know as nothing physical has ever surfaced, not even a photo. What is fact and real as the above shows, is how the 2000 was given life, truly remarkable (for me) to behold.

As I say I suspect others have already seen it but for those like me who have not and might also be interested, I thought I would post this thread.

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Topic starter Posted : 30/12/2016 6:19 pm
Cathovisor
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Yes, I bought The Setmakers when it was first published and I remember that photo well. I've seen slightly tidier scenes at my former workplace when my colleagues were able to develop their own test equipment for specific jobs; the one that sticks in my mind was the "Virtual Tape Machine", which was a variable-speed linear timecode generator used to check the performance of tape machine synchronisers in dubbing suites. It even had an in-vision timecode inserter and could be switched between 25 and 30 frames/sec.

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Posted : 30/12/2016 7:27 pm
Lloyd
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It looks just like my workbench in my old workshop! rolf_gif

How did they ever make sense of all that, and come up with a working TV?! I bet there were a few electro_gifalong the way! Certainly interesting to see how it all came together.

 

Regards,

Lloyd.

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Posted : 30/12/2016 7:46 pm
Till Eulenspiegel
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That's what we like to see, proper TV engineering, non of this digital screwdriver stuff.  Wish I still had the pictures of my standards converter project dating back to 1984.  It was a great big organised mess on the workbench.  The converter was never the same after it was tidied up.  The original 1985 converter is alive and well under the safe keeping of another forum member, and to think it was going to be chopped up for spares in 1990.

Till Eulenspiegel.

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Posted : 30/12/2016 9:06 pm
Red_to_Black
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Now that is what I call a 'Lash up' frightgrin_gifelectro_gif

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Posted : 30/12/2016 10:21 pm
Jayceebee
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Thanks for sharing that Chris, not seen that picture before. Amazing, what a rats nest, nothing recognisable in that and the finished product to me. Just as well it came with a caption, wonder what the Bulldog clip does?grin_gif

John.

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Posted : 30/12/2016 10:23 pm
Till Eulenspiegel
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There is follow up pictures in the Setmakers book of the development of the 2000 series, up to stage where it looks recognisable as the chassis we all know well.  

Till Eulenspiegel.  

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Posted : 30/12/2016 10:36 pm
Nuvistor
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Certainly don't want the cleaner coming in and tidying up. I never worked on the 2000, saw the odd one in the shops. Only  ever repaired a a few of the 3000 chassis, we didn't sell Thorn sets so I did not get them in to repair. 

It was certainly an achievement, I read that Thorn and Texas collaborated closely in the power transistor stages, with special types used.

Frank

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Posted : 31/12/2016 1:36 am
ntscuser
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Chris said

I have heard of a mythic Thorn 1000 being mentioned by folk here and elsewhere, that it was mainly valve. Whether this was ever built of is just an urban legend, I guess we will never know as nothing physical has ever surfaced, not even a photo.

From the TV at the Shows report, Practical Television October 1966:

BRC-colour-receiver-1966.png

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Posted : 31/12/2016 1:45 am
turretslug
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Ah, but where's the half-cup of cold coffee and (bearing in mind the era) the ashtray? When I started working life at a test-bench in the mid-'eighties, smoking was just an accepted part of the everyday scenery. Seems shocking now. I like the use (up-cycling?) of the retort stands/clamps. I reckon there's a quiet insurrection going on there- every time he turned his back, all the test-gear shuffled forward another half-inch.

I can't say that any test set-up of mine got quite like that, but there were quite a few occasions when I thought, all it needs is a sneeze and there'll be a fireworks display. I wonder how many expensive and exotic semiconductor junctions were sacrificed in the name of progress there? There must have been a time when even the suggestion of using the fragile newcomers in applications like LOP stages and beefy RF PAs must have seemed like doomed and profligate madness but it happened in the end, even if existing ideas on topology had to be torn up for a fresh start. The sad thing is, the advent of ever-smaller and specific components, SMD and over-bearing safety fears probably dissuades many from the satisfaction of lash-ups that (eventually and satisfyingly) work.

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Posted : 31/12/2016 10:49 am
Till Eulenspiegel
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From the same page the first picture was taken from. Showing the almost complete receiver and the removable modules to facilitate ease of servicing.  

Till Eulenspiegel.DSC_0116_41.jpg

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Posted : 31/12/2016 12:00 pm
Katie Bush
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I somehow feel compelled to say, these still look quite modern, even at fifty years on - either an enduring construction model, or my feet are still dangling the waters of five decades past?

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Posted : 31/12/2016 11:04 pm
Till Eulenspiegel
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BRC 2000 is my favourite early colour TV set.  Thorn took a chance on advanced transistor technology.  The others took the safe route and used valves.  Bear in mind in the mid sixties much of industry was moving away from valves.

Just how did the BBC modify the 2000 for baseband monitor?    Check out the circuits of the chroma and luma signal paths, the design does not lend itself for such modifications.

Till Eulenspiegel.

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Posted : 01/01/2017 12:02 am
Nuvistor
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I can't say it was mine, did not sell them but it was pushing the envelope as they say. They took a gamble and it paid off, it helped that they had lots of rental shops of various brands to push what they could make but all set makers had small runs.

I always thought the picture was below the standard of some of the valve sets (not the Bush CTV25 though), but that may be me. They built on it with the 3000, others took 5 years to get to that stage.

In the end they suffered the same as the rest of the industry.

Frank

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Posted : 01/01/2017 1:36 am
Katie Bush
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Bush CTV25? I had one of those! a 1968 dual standard model, and what a disappointingly poor picture it produced - poor focus, lack of definition, wishy-washy colour and poor contrast.. It looked liked a pastel water colour! - Not a patch on the G6!

I never had a 2000, but did once own a 3000 (or was it 3500?) pretty certain it was a 3000, and that was a fair performer, but was well worn out, and to my disappointment, the CRT was as flat as pancake, but freshly bopped to catch the unwary. I never fell into that trap again.

Even in the mid 70's it was still a bit weird to take the back off a set and not find a valve in sight, but most striking, from a visual standpoint, was the lack of all the heavy duty EHT generation equipment associated with the hybrids.

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Posted : 01/01/2017 1:50 am
crustytv
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Over the past few years I've often encountered folk (present company excluded) who speak quite spitefully and in a critical manner towards Thorn sets. I was never in the trade so I guess I've no right to comment, I'm just an keen amateur who collects and repairs early CTV and has quite a few varied examples to compare to.

As an outsider looking in I'm in awe of Thorn and the design engineers. They were the first with all transistor CTV, the first with the * modular approach, they certainly made the service engineers life easier with that.  The first with switched mode power supply (3000) First with the sub £200 CTV for the masses (8000) then there was SYCLOPS. Also lets not forget the most successful and popular chassis of the entire 70's was the 3000 ( confirmed in a recent publication find). Then they carried on with the very successful TX chassis.

This is why Thorn sets feature quite strongly in my collection and why I've tried to get most if not all the chassis examples of the first decade. All I'm missing is a 4000, OK I know most spit flames when the 4000 is mentioned but its a worthy addition to seek. There's probably more pre war sets than 4K sets to be found and perhaps its even an extinct set.

* Telefunken took that to a new level with the 71x chassis.

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Topic starter Posted : 01/01/2017 2:16 am
Nuvistor
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Hi Chris,
I won't take anything away from Thorn for the bold move of the 2000 chassis. To me it was a very surprising move, their BW sets were cut to the bone for their big rental chains, rent as many as possible, as cheap as possible, I thought they would have done the same with the CTV, but perhaps Sir Jules was after prestige like the other set makers were.
The modular approach was probably driven by that market for fast repairs in the house, it would be interesting to know how many took advantage of this or were repairs done on the PCB's like any other repairs due to costs of stocking the modules.

There is no doubt that those BW sets were easy to fix, and their LOPTX's have stood the test of time. I just found the reliability and the performance of BW sets was not as good as other makes, this was why we did not go for the Thorn CTV, perhaps we were wrong.
Has for the picture quality of the 2000, I can only go off what saw, the Pye, GEC and I think KB were much better, again a personal opinion. There were new sets so not down to ageing.

Thorn were certainly a leader in solid state TV and it took years for others to do the same.

Frank

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Posted : 01/01/2017 8:31 am
Nuvistor
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Hi Marion,

I don't know if that CTV25 was new or S/H but when new the pictures were poor compared to the Pye and GEC chassis, we also had the LOPTX fiasco putting Davy lamp mods on them, at least it made them safer.

One of the best pictures I saw but we did not stock them was the first Baird CTV, the circuit looked very American but for the PAL circuit, no reason that the rest of the design could not be similar apart from timebase speeds and video response. Lots of valves in that though. 

Frank

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Posted : 01/01/2017 8:43 am
crustytv
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nuvistor said

One of the best pictures I saw but we did not stock them was the first Baird CTV, the circuit looked very American but for the PAL circuit, no reason that the rest of the design could not be similar apart from timebase speeds and video response. Lots of valves in that though. 

Frank  

Hi Frank,

Totally agree and I said as much in my Baird 700 series repair thread. Of all the sets in my collection I would say the Baird is probably the best and it resolves the 5.25 frequency grating. Not bad for a set that will be 50 this year, its cabinet stamp date being 20th December 1967.

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Topic starter Posted : 01/01/2017 11:26 am
Katie Bush
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Hi Frank,

The CTV25 was second hand, and about ten years old when I got it. I acquired it as part of a job I did for a couple who'd just recently moved in to the house across the road. They'd bought a new telly when they moved, and the old Bush was going spare.  At the time, they needed a small amount of tractor work to be done (very large "back garden").  I happened to mention I'd been fancying a Bush CTV for a while (can't really think why!doh_gif) - anyway, it was mine for the taking, not that it ever was much good, but in its favour, it had been very well looked after by its previous owner, a retired ex WW2 spitfire squadron leader, no less!

I remember the set had no colour at all when I took it on, and needed the assistance of greater minds to resolve that problem. The first thing I saw on that set was "The Yellow Submarine" and the set spent Christmas in my parents living room, after which, I gave them the GEC 2028 and took the Bush to my room - big mistake, mum and dad had by far the better telly!nuts_gif

Then the colour 'snuffed out' again, and that was that, back to a good old G6.tele07_gif

The Thorn 3000 came as a stop-gap when my best G6 had a flare up - I thought I'd go solid state but had no idea that the CRT was shot, nor that it had been bopped to Hell and back, so we built a bopper (as you do) and gave it a tickle, the picture was a corker, for all of a couple of hours then flat again, so my granddad did a bit of a mod to the bopper, and with the aid of a couple of meters was able to determine that the CRT was kaput - I wish I could remember how that mod went. Anyway, we didn't have a CRT to fit, and there were other disincentives to fettling up the 3000.  In the end I used a PYE 697 for a year or two, but the advent of my N1700 VCR meant I really wanted a better telly to go with it - one that would 'sync up' for a start, so that brought about my PYE badged KT-3, one of the best and most reliable tellies I ever owned.

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Posted : 01/01/2017 9:42 pm
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