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Windsor 240A TV pattern generator

 
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Windsor 240A TV pattern generator

Post by AidanLunn » Fri Jan 29, 2016 12:47 am

Hello all

I'd like to pick the brains of fellow members.

I've just begun restoring one of these pieces of setup equipment, however I have never restored one of these before, and I cannot find service information for these (I haven't checked in the library, to be honest), so I don't know if the restoration is completed or if there are further faults.

So my question is, did TV pattern generators of the period (late 1940s/early 50s) really display patterns as basic those on the screen of the Sony 9-90UB? I'm not expecting a complete test card or anything of the ilk, but were they not advanced for full crosshatches and so on?

Many thanks for any help offered :)
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Re: Windsor 240A TV pattern generator

Post by Terrykc » Fri Jan 29, 2016 11:45 am

AidanLunn wrote:... did TV pattern generators of the period (late 1940s/early 50s) really display patterns as basic those on the screen of the Sony 9-90UB?
In a word, yes!

When I started work in 1960 there was a dusty pattern generator on the shelf that did basically the same as yours, although it might have had the option to generate both patterns at the same time - your's obviously can't according to the selector markings.  I think I once switched our's on out of curiosity to see what it did. With test card transmissions virtually all day every day there was no need for such crudity anyway, and it went back on the shelf to gather even more dust!
AidanLunn wrote: I'm not expecting a complete test card or anything of the ilk, but were they not advanced for full crosshatches and so on?
Again, in a word, no! Look at the (lack of) complexity in yours - it could hardly be much simpler!

These generators didn't even produce sync pulses!  They simply generated square waves - as you can see - at multiples of line or field frequency with the hope that a TV would lock on to an appropriate sub-multiple. Sophisticated these devices were not! 

Consider the relative complexity of dividers for locking the pattern to sync pulses, even if line and field rates were free running with respect to each other. The cost of such a device, produced in small numbers, would have been very high - I doubt the simple model you have there would have been particularly cheap!

There wasn't really any demand for pattern generators on a large scale until colour arrived. Even then there were some horrors around!

We tried a couple that went back pronto! Then we bought the RBM generator with its broadcast standard sync pulses which was a comparative revelation.

I think the manual for that might be in the Technical Library. If it is, take a look at it then strip out the dual standard stuff and convert what you have left into a schematic for a valved version.

If you then fancy building it, you might want to start off with a bigger case ...

 
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Re: Windsor 240A TV pattern generator

Post by Cathovisor » Fri Jan 29, 2016 1:33 pm

Terrykc wrote:These generators didn't even produce sync pulses!  They simply generated square waves - as you can see - at multiples of line or field frequency with the hope that a TV would lock on to an appropriate sub-multiple. Sophisticated these devices were not! 

I think you do some generators a massive disservice, Terry.

First and foremost amongst television pattern generators was the Murphy TPG11. This produced correctly-interlaced sync pulses along with a useful pattern. Versions of this were actually used by the BBC as a pattern generator for OBs, testament to their quality IMO. The trouble with the TPG11 was its price - it was very expensive and thus way out of the reach of the average low-rent TV mending establishment run on a penny-pinching shoestring.

There were also the Radar 405 and the Telequipment WG/44, which also produced correct sync pulses and a usable test pattern - these are all late 40s/early 50s devices, by the way. Later in the mid- to late 1950s we had the Taylor 94A, which was multi-standard and again, produced correct sync waveforms.

These poor examples are fit only for looking at and even then, held no place in any workshop that attempted serious service. To quote F. Livingston Hogg in the section on servicing equipment in the Television Engineers Pocket Book:

F. Livingston Hogg wrote:The writer makes no apology or attempt to conceal the bee in his bonnet on this matter. He considers that no one should have the temerity to attempt television servicing commercially without a pattern generator, and, furthermore, that any pattern generator not conforming fully to B.B.C. standards should not be allowed on the premises!


I have pictures of the patterns produced in these devices but no easy access to a scanner at the moment...

 
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Re: Windsor 240A TV pattern generator

Post by Terrykc » Fri Jan 29, 2016 1:46 pm

Terrykc wrote:... Then we bought the RBM generator with its broadcast standard sync pulses ...
Apologies - I'm getting confused with a fully fledged colour bar generator of German origin (Grundig, possibly?) that I became acquainted with a few years later. This had a densely packed PCB containing, amongst a lot of other things, a number of blocking oscillators in the sync divider chain to give the correct line/field timing, etc.

The Rank generator, nevertheless, had rock steady sync performance achieved with a number of multivibrators.

The model number is T55 and, as I thought, is in the Technical Library under Test Equipment in the Service Data User Manuals & Related Technical Data folder.

 
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Re: Windsor 240A TV pattern generator

Post by Cathovisor » Fri Jan 29, 2016 1:49 pm

Terrykc wrote:
Terrykc wrote:... Then we bought the RBM generator with its broadcast standard sync pulses ...
Apologies - I'm getting confused with a fully fledged colour bar generator of German origin (Grundig, possibly?) that I became acquainted with a few years later.
There was certainly a Körting generator (I have one), which was also badged as a Decca and unusually, did NTSC4.43 as well!

 
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Re: Windsor 240A TV pattern generator

Post by Terrykc » Fri Jan 29, 2016 2:22 pm

Cathovisor wrote:... I think you do some generators a massive disservice, Terry.

Only if you take my comments out of context:

I said "... the cost of such a device, produced in small numbers, would have been very high ..." which is in total agreement with your comment about the Murphy generator:

Cathovisor wrote: The trouble with the TPG11 was its price - it was very expensive and thus way out of the reach of the average low-rent TV mending establishment run on a penny-pinching shoestring.

Also, as I said, the almost total availability of broadcast test cards negated the comments towards the end of your post.

After all, there is no substitute for the real thing!

Of course, there is always the exception ...

I'd just changed the tube in a Bush TV53. Unusually for that time of the afternoon, there was programming on both BBC and ITV (Croydon) but we could get a signal, albeit rather grainy, from the Dover transmitter - which was showing Test Card C.

The line linearity on this set was appalling - I'd never seen anything like it on one of these sets! I spent absolutely ages trying to improve matters - which I did - but it was still far from perfect. By this time I noticed on another set running on soak that Croydon was now transmitting a test card, so I switched to channel 9 ...

What I saw was diabolical line linearity but in the opposite direction to what I'd been seeing on channel 10! It didn't take long to reset my previous 'improvements' and I now had a perfect test card on channel 9 but a bad one on channel 10!

Then there was a slight twitch on the picture from Dover and, in a few moments, someone had managed to correct the problem that was obviously affecting the slide scanner at Dover - if only they'd noticed it an hour earlier ...!


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