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Old 09-11-2017, 04:42 PM
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Conrac broadcast monitor - please help identify exact model, where to find?

Hello everyone,

I am trying to correctly identify a Conrac color broadcast monitor (see picture) and was hoping someone would be able to point me in the right direction.

About 25 years ago I was given this exact monitor as a gift by my high school physics teacher who wanted to get rid of it since it was taking up too much space in his small prep room. The monitor was in mint condition and had very low hours - someone must have purchased it for some long forgotten purpose and never gotten around to using it.

I used it as a color display for my first PC and was very happy with its performance and the fact that I had gotten it for free! It came with a detailed manual that included parts lists and schematics which helped me a lot trying to figure out how to hook it up. If I remember correctly, it had at least a 19" screen and was made some time in the early to mid 70s. Unfortunately, when I left for college a few years later, my parents re-purposed my room and couldn't wait to get rid of 'that eyesore' and put it out to the curb (including the manual).

I do not remember the exact model/type, but I do remember that it had 5 BNC connectors on the back, R, G, B, H, V, which worked wonderfully for the PC setup. The colors on this monitor were unlike anything I had seen on a screen before - really bright and vibrant, almost 'radioactive'. It had a ton of knobs behind the top panel that would allow for adjusting the convergence, and knobs at the bottom for hold, linearity, brightness, contrast, etc. It had a modular build - everything was neatly tucked away under aluminum covers - and very high quality of craftsmanship.

For many years, I was completely unable to find any documentation about this beast until a few weeks ago when I stumbled across a post by some urban explorers who were taking pictures inside a decommissioned nuclear power plant - lo and behold, in the middle of the reactor control room sits my long-lost monitor!

If anyone can positively identify the exact model, I would be very grateful. Furthermore, if anyone knows where to obtain one (my ebay, industrial surplus, google, auction, etc searches have failed me) and would like to share that information with me, that would be absolutely amazing.

Thank you for your consideration!

(the picture is courtesy of imgur user "zooooooooo" - thank you for finding this!)
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Old 09-11-2017, 05:41 PM
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A great nostalgia piece.

You are right, the tube would be 19 inch diagonal, which was the largest that would fit into a 19 inch wide rack mount. As for color, the tubes were made with calibrated phosphors, which had accurate colors, but no more color gamut than a current HDTV set. A lot of the picture quality came from having perfectly stable black level plus stable high voltage and therefore perfectly steady scan with no "breathing" whatsoever with video content. IIRC, these sets had separate horizontal sweep and high voltage supply circuits. The contrast capability was less than current LCD displays, depending on the amount of room lighting reflecting from the CRT face. Some additional image quality was due to the phase-linear video peaking circuitry, too expensive for consumer sets until digital video processing came along. These monitors, however, did not have comb filters, and therefore suffered some loss of resolution due to the chroma subcarrier trap, which could be switched off for monochrome use.
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Old 09-11-2017, 05:59 PM
J Ballard J Ballard is offline
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This is the same form factor as the composite version, either a type RHA or RHB. Perhaps an RHN? Give me a few days and I''ll dig into my Conrac file.

The horizontal frequency would have not been much higher than standard NTSC, and as Wayne suggests, it came with stable black level circuitry and a controlled phosphor CRT, probably made by RCA.

The composite models had a notch decoder; the model after this had an optional comb filter decoder.

Conrac made "computer" monitors for higher scan rates-the QQA (monochrome) and the 7211 color model.

That was many moons ago..

JB
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Old 09-11-2017, 09:33 PM
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Oops - got off the track a bit talking about the composite version. Now I can't recall if the composite version also had RGB inputs in addition to the composite input.

One thing I think I recall about color accuracy in the composite version - they used the output of the R-Y and B-Y color difference demodulators to measure the burst phase (R-Y should be zero on burst) and therefore can have no phase error between the PLL and the demods.
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Old 09-12-2017, 02:10 PM
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Good afternoon,

Thank you all very much for the information you have provided so far!

I was able to use the model description to find out a little bit more about this monitor. My university library has quite a handful of links to scientific articles that mention the RHB (sometimes also referred to as "RHB/19" or "RHB/19C") as being used as a reference monitor. Apparently, the calibrated phosphors allowed for reproducible experimental results across research institutions.
I found articles from the mid 70s to early 80s that range from medical to meteorological all the way to aviation and defense-related fields. I also learned that the SMPTE-C color space owes its existence to efforts made by Conrac (hence the C) to push manufactures to use standardized phosphors - very impressive!

As far as my monitor was concerned, I do not recall it having a composite input(s) - maybe I never tried to use it, as the R, G, B, H, V connections were all I needed - but I may be completely mistaken...

One detail I didn't mention before and which just came back to me: my particular model did not have a contrast control. Maybe it was omitted at the factory because of the original requirements of the person who purchased it, or the lack of a contrast control makes this one a different model altogether. Either way, I remember connecting a variable resistor according to the schematics, but it never worked quite right - the picture would take on a yellowish hue when the contrast was increased.

Once again, all your input and suggestions are greatly appreciated. I am looking forward to learning more from you.

Have a great day!
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Old 09-12-2017, 03:45 PM
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GREAT Score! Glad to see another piece of TV history bein' saved... This is, at once, the greatest era in human history-And the WORST...Historians in the future will no doubt marvel at the primitive items we've produced- But will fuss & cuss LOUDLY that virtually None of it has been saved. Imagine having a WORKING TK-41/CT-100 camera chain 75, 100 years from now..
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Old 09-12-2017, 05:19 PM
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Quote:
Originally Posted by Sandy G View Post
GREAT Score! Glad to see another piece of TV history bein' saved... This is, at once, the greatest era in human history-And the WORST...Historians in the future will no doubt marvel at the primitive items we've produced- But will fuss & cuss LOUDLY that virtually None of it has been saved. Imagine having a WORKING TK-41/CT-100 camera chain 75, 100 years from now..
I don't see anywhere in this thread where anything has been saved....

Those monitors do look like they would be neat to have....If Physicist sneaks into the abandoned nuke power plant that pic is from, saves both those monitors and wants to unload the one that glows in the dark more I might be interested.
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Old 09-12-2017, 06:02 PM
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Quote:
Originally Posted by Electronic M View Post
I don't see anywhere in this thread where anything has been saved....

Those monitors do look like they would be neat to have....If Physicist sneaks into the abandoned nuke power plant that pic is from, saves both those monitors and wants to unload the one that glows in the dark more I might be interested.
If I remember correctly, that nuclear power plant is located in one of the Carolinas. Interestingly enough, it never went online, but was decommissioned before the built was finished. In other words, all the stuff in there, including the monitor, is absolutely mint (aside from sitting around for some 25 odd years). The government works in mysterious ways, I guess...
Either way, the ownership of the plant and the equipment is, at best, unclear, so going in there and taking stuff is most likely considered theft. What a shame
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Old 09-12-2017, 06:27 PM
J Ballard J Ballard is offline
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In today's New York Times, Sept. 12, there is an obituary for producer Don Ohlmeyer. Don is shown in an NBC mobile unit, and behind him are three 19" Conrac RHB color monitors, the composite analog versions of the one shown earlier.

JB
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Old 09-14-2017, 11:42 AM
kf4rca kf4rca is offline
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Conrac RHA for sure. They were once the mainstay of TV stations until the ultra rectangular tubes came out (about 1980).
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Old 09-14-2017, 12:39 PM
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The more I see of that pic the more I think of the movie 'The China Syndrome'.
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Old 09-14-2017, 04:11 PM
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Quote:
Originally Posted by J Ballard View Post
In today's New York Times, Sept. 12, there is an obituary for producer Don Ohlmeyer. Don is shown in an NBC mobile unit, and behind him are three 19" Conrac RHB color monitors, the composite analog versions of the one shown earlier.

JB
Rest in peace, Mr. Ohlmeyer.
J Ballard, you are very sharp-eyed! Thank you very much for pointing out that these particular monitors are the RHB type. This will help a lot in my quest to find out more about the monitor I used to own.
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Old 09-14-2017, 04:13 PM
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Originally Posted by kf4rca View Post
Conrac RHA for sure. They were once the mainstay of TV stations until the ultra rectangular tubes came out (about 1980).
kf4rca,

Thank you very much for the clarification. I will now be able to narrow down my search for this particular type!
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Old 09-14-2017, 04:16 PM
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Quote:
Originally Posted by Electronic M View Post
The more I see of that pic the more I think of the movie 'The China Syndrome'.
It sure carries some sort of doomsday vibe. I wouldn't have been surprised if this picture was taken in some abandoned missile silo as opposed to a nuclear power plant.
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Old 09-18-2017, 10:27 AM
kf4rca kf4rca is offline
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The RHA's were very heavy.

If the rack wasn't bolted to the floor, when you extended them on the rack slides, the rack would want to topple over on you.
The RHA's were all transistor (no IC's). The model before that was the CYA which was hybrid and used a 17" tube. Lots of these monitors were tossed out simply because TV stations were in a rush to convert to all transistor equipment and get out from the ever increasing price of vacuum tubes. Conrac CYA attached.
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File Type: jpg CYA.jpg (54.4 KB, 22 views)
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