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Old 30th Sep 2017, 7:05 am   #1
Argus25
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Default The world's greatest monochrome video monitor.

While this sounds like a pretty bold statement, I think most will agree after reading the article. I have been researching this extraordinary monitor for some months and written an article about it.

I have included a technical description in the article on how the brilliant & unique black level controller in it works. I have also added additional screen photographs, including some from The Time Tunnel, and a remark about the uncertainty principle.

For anyone interested and TV & video monitor design, I hope this makes for an interesting read.

http://worldphaco.com/uploads/The_19...o_monitor..pdf
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Old 30th Sep 2017, 10:32 am   #2
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Default Re: The world's greatest monochrome video monitor.

Yes a most impressive monitor, I hate to think what it must have cost! The ordinary Conrack build quality is high but this one is an order of magnitude higher.

Is there a model number for it?

Your explanation of the black level clamp operation was very clear.
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Old 30th Sep 2017, 11:01 am   #3
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Default Re: The world's greatest monochrome video monitor.

Excellent writeup.
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Old 30th Sep 2017, 12:00 pm   #4
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Default Re: The world's greatest monochrome video monitor.

Most interesting piece of "engineering confectionery"- perhaps for LLTV or similar night use in large aircraft, a few possible applications come to mind (say KC135/AC130- type application?) with the green screen, the use of 625 lines suggests that off-the-shelf monochrome tape recorders of the era could be used for de-briefing/mission review at a later date- I saw Sony machines of the time (late seventies, forget the model number) used for military purposes. Airborne kit can be a good illustration of how to make things both strong and light, ground/marine kit is frequently somewhat unsophisticated, even brutish in construction!
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Old 30th Sep 2017, 12:21 pm   #5
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Default Re: The world's greatest monochrome video monitor.

That is a pretty spectacular piece of over-engineering. If I had to guess at the design process, I'd say that the avionics requirements for maintainability lead to having loads of connectors and fasteners, and it then becomes a challenge to design the reliability back in. I wonder, mischievously, whether a cheapo paxolin PCB jammed into a plastic box would have been any less reliable in practice!

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Old 30th Sep 2017, 2:14 pm   #6
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Default Re: The world's greatest monochrome video monitor.

What a lovely monitor! And nice work reverse-engineering the schematics. You have more patience than me!


In detail it reminds me quite a bit of the big metal-cased "SIGMEX" CRT displays I saw used in geomagnetic survey aircraft in the 1980s.
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Old 30th Sep 2017, 8:08 pm   #7
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Default Re: The world's greatest monochrome video monitor.

Quote:
Originally Posted by paulsherwin View Post
Excellent writeup.
Thanks kindly for that remark. It sure took a while to document the circuitry too. Some of the parts I was already familiar with, like the 10101 OP amps etc, which are just mil spec 741's. A lot of the resistors & caps are special quality parts and the values are not clear from the number systems on them.

Beamcurrent; the model is a 61414, which I think relates to the 14" screen size it probably came in other screen sizes.
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Old 30th Sep 2017, 8:13 pm   #8
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Default Re: The world's greatest monochrome video monitor.

Quote:
Originally Posted by cmjones01 View Post
I'd say that the avionics requirements for maintainability lead to having loads of connectors and fasteners, and it then becomes a challenge to design the reliability back in.
Chris
Yes, the additional D connector for the yoke could be a good example. However it is very handy where they placed it, it has a spring clip that slides back and forth to release it, and it makes it a dream to remove the CRT and yoke assy.
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Old 1st Oct 2017, 7:35 pm   #9
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Default Re: The world's greatest monochrome video monitor.

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Originally Posted by turretslug View Post
perhaps for LLTV or similar night use in large aircraft, a few possible applications come to mind (say KC135/AC130- type application?) with the green screen
Maybe overlooking a more obvious candidate in that the Australian military were contemporary users of the US-made and -equipped P3, with a clear case for LLTV and observer. Just curious as to the application!
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Old 1st Oct 2017, 11:02 pm   #10
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Default Re: The world's greatest monochrome video monitor.

I noticed on the test data sheet that came with it, it says : Instrument Nomenclature...Imagery Interpretation System IIS Display. But I have no idea what that means.

Also it says it can produce 7 shades of grey but it is just standard analog video capable with every shade of grey.

The display linearity accuracy is quoted as less than or equal to 2% (presumably errors) for H deflection and less than or equal to 1% for V deflection which is pretty good.

Brightness quoted at 43,5 foot Lamberts, 30 min. Power 50W and weight 42lbs, that is about all the info there is.

The unusual thing is that it displays either 525 line 60Hz or 625 line 50Hz, without the need for standards switching, so I still don't know which one it was intended for. On 525, 60Hz the height is lower and its full screen on 625, 50Hz. But on 625, the H hold control needed adjusting for perfect picture centering.

The UJT based vertical oscillator has a very wide lock in range as does the Horizontal AFC circuit. And the UJT vertical oscillator was originally set to run slower than 50Hz which explains why/how it can lock to either 50 or 60Hz vertical syncs. This also explains why, unlike most monitors, the H and V hold pots are just presets on the pcb set at the factory. When I first saw the monitor my first thought was, where are the H & V hold controls ?
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Old 2nd Oct 2017, 12:59 am   #11
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Default Re: The world's greatest monochrome video monitor.

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Originally Posted by Argus25 View Post
I noticed on the test data sheet that came with it, it says : Instrument Nomenclature...Imagery Interpretation System IIS Display. But I have no idea what that means.
Google gives plenty of hits for Image(ry) Interpretation System and several of them are US Air Force related.

This one for example.
http://lib.dr.iastate.edu/cgi/viewco...0&context=qnde

Dealing with Neutron Radiography of aircraft wings, although clearly that particular test facility wasn't itself airborne.
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Old 2nd Oct 2017, 1:38 am   #12
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Default Re: The world's greatest monochrome video monitor.

Since this system wasn't for airborne ops, but uses the term IIS, it looks like the terminology of IIS could be for any type of image display system, airborne or not. It might just be what civilians call the video display but in these mil & air force cases the video signal could be practically anything depending on the application.
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Old 14th Oct 2017, 1:12 pm   #13
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Default Re: The world's greatest monochrome video monitor.

I have discovered the origin of or at least the probable early publication of the unique video black level controller in the monitor.

I might have guessed I suppose, where it could have come from given the total mastery that Tektronix has over discrete circuit design, so in many ways I'm not surprised. I stumbled across the article in a 1969 vintage Tektronix publication while looking for something else!

I have added it to the article at the end, so scroll down to that. It will make an good read for those interested in video signal processing:

http://worldphaco.com/uploads/The_19...o_monitor..pdf
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Old 14th Oct 2017, 2:00 pm   #14
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Default Re: The world's greatest monochrome video monitor.

Interesting that they bothered with the elaborate clamp system to eliminate drift in the final video amplifier, when presumably the CRT has a fair amount of drift in its own characteristics. With such a high-end design I'm now a bit disappointed (!) that they didn't go all the way and put an auto black level compensation arrangement in like colour TVs had from the late 80s onwards.

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Old 14th Oct 2017, 2:16 pm   #15
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Default Re: The world's greatest monochrome video monitor.

Well I guess it is only one of the functions of the circuit to eliminate the drift in the output amp, the main function is to fix the black level of the video signal at a fixed voltage on the CRT's cathode.

It is interesting that a good number of commercial TV's didn't even have a DC restorer or black level clamp, particularly early transistor sets, where the video out simply went to the CRT cathode via a capacitor, they are really annoying to watch. If they are set up for proper contrast & brightness on a normal scene,then on low brightness scenes the image washes out as the background level is too high.
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Old 14th Oct 2017, 10:57 pm   #16
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Default Re: The world's greatest monochrome video monitor.

Quote:
Originally Posted by Argus25 View Post
I might have guessed I suppose, where it could have come from given the total mastery that Tektronix has over discrete circuit design, so in many ways I'm not surprised.
Agreed- working with a variety of Tek gear over the years, there was little doubt that there were some maestros of elegant and effective electronic design working for them, there was an impression of sheer depth and thoroughness of understanding of circuit action. I'm not of the era when their thermionic stuff was in active service, so to speak, but their semiconductor era products were benchmark stuff. The mechanical design and construction was most impressive, too, sturdy yet not profligate of weight, material or complication. I've long been a fan of effective precision mass production- I'd argue that the Model T has greater relevance to the 20th century than the Silver Ghost, as an example- and the USA were exemplars of how to do it, whether the budget was pitched at AA5 or R390A level.
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Old 14th Oct 2017, 11:35 pm   #17
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Default Re: The world's greatest monochrome video monitor.

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The mechanical design and construction was most impressive, too, sturdy yet not profligate of weight, material or complication.
Yes, Tektronix seem to have aced the design of nearly everything they turned their hand to. One thing I really like about their gear (I particularly like their scopes and generators late 1970's to mid 1990's, post vacuum tube designs) is the way it was so well documented in their manuals. Also their statement on the characteristic Tek blue color manual covers " Committed to Excellence" under their logo, and it really was true.

One of their products was a small plug in oscilloscope the SC502 that plugs into their TM500 series power frames. The combination of physical & electrical excellence and they way they put it together in that small housing is nothing short of mind blowing. A lot of it was that they were not happy to use off the shelf parts from other companies, because they were not good enough. So they made a lot of the important parts like wide bandwidth signal IC's and the CRT's and switch assemblies themselves.

Many companies now don't manufacture special sub assemblies for their test gear like Tek did and they are just constructed from generic parts and a lot of design challenges are now in the software rather than the hardware.
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