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 Post subject: Diagrams in the RCA RC-30 book
PostPosted: Mar Sun 22, 2020 7:49 am 
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Location: Arvada, CO
Has anyone attempted to create some of the circuits in the RC-30 book? I just wanted to see if anyone has tried them. I am attempting at the Black and White television (Without the IF and tuner of course.) These circuits seem to have a deal of flexibility. Thank you!

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 Post subject: Re: Diagrams in the RCA RC-30 book
PostPosted: Mar Sun 22, 2020 4:28 pm 
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Joined: Jan Tue 16, 2007 7:02 am
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Location: Lexington, KY USA
I think that most of the RCA tube manual circuits can work. There may be some typos that you would need to find. Many were based on one or another production RCA set or instrument.

The problem for construction with these example circuits, is that they require specialized coils and transformers that were usually not full specified, and now are no longer made anyway.

For something like a TV, you would need to source these components, then deal with chassis layout, lead dress, and adjustment. Might best be viewed as an educational project.

Ted


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 Post subject: Re: Diagrams in the RCA RC-30 book
PostPosted: Mar Sun 22, 2020 7:29 pm 
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Those are the problems I had. I found that Talon Electronics had many of the original parts (Flyback, Vert. Out Transformer, Horiz. Stability coil, Thermistor). You can use the Sams to cross-reference the parts to other manufactures. That's what I did for the yoke. There also were the typos too. In the manual, it listed the video peaking coil as 18uh. However, further research in Beitmans and Sams found that it was 180uh. Otherwise, that was the only typo I found (besides a few selling errors). They also left out the picture tube circuitry. That meant a picture tube substitution was possible. The manual called for a 16BGP4/16AYP4. I wanted a slightly larger picture tube with mounting rims, so I chose the 19EKP4 tube. The only change would be different voltages for G2 and G4 voltages. Lack of mounting specifications meant other tube subs that were cheaper. The Novar tubes were never popular, only used mostly by RCA. So, while the tubes are plentiful, the sockets are not. Compactron sockets are much more common, so I cross referenced the Novar tubes to Compactrons. Also, since I cut out the tuner and IF sections, the series string filament voltage would be short of the line voltage. So using higher filament voltage Compactrons would help that. Here is the substitutes:
22JU6--17JM6
17BS3A--34CE4/34CD4
15KY8--21LU8
8FQ7--8B10 (Substituted because 8B10 has phase detector diodes and triode sections are similar)
11LQ8 & 1/2 6GH8A--15AF11
6HZ6 & 12FX5--13J10/13Z10 (Used because of higher audio power wattage versus 17BF11 etc.)
1B3/1G3--1J3/1K3 (Practically interchangeable besides voltage drop and safely mechanism in case of filament to plate short)

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 Post subject: Re: Diagrams in the RCA RC-30 book
PostPosted: Mar Wed 25, 2020 2:07 am 
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Really a very ambitious project ! I guess it can be done but the real challenge would be collecting all the necessary original RCA special parts... 47 years later ! Also, these were basic illustrative purpose circuits without any construction details, circuit layouts, alignment instructions, etc... a very good experience in building RF/IF circuits from scratch would be needed but I expect any good experienced old HAM will be able to successfully complete such a project. I allways wondered if anyone then ever attempted to actually build the most complex circuits which can be found at the back of these RCA tube databooks. In the RC-28 there's is a schematic for a complete color TV using no less than 30 tubes ! But there's also the following warning note:

"Circuits xxx through yyy are included in this manual primarily to illustrate applications of RCA electron tubes. Because of the exceptionally high voltages (up to 21,500 volts), high frequencies and large bandwidths that are required and of the many special components that are used, home construction of these circuits is not recommended."

Anyway, please keep us posted about your progress. This is quite an interesting and unusual project.


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 Post subject: Re: Diagrams in the RCA RC-30 book
PostPosted: Mar Thu 26, 2020 8:43 am 
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Location: Arvada, CO
If I could, I would. However, the unobtanium is much greater in a color set rather than a black and white. RCA also advised against it for home construction, as much alignment equipment that I do not have is needed for the coils. I am sure a color TV servicemen with a large selection of TV parts and testing equipment would be able to pull it off.

All right, enough speculation from me. Will keep posting updates on the Homemade B/W set

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 Post subject: Re: Diagrams in the RCA RC-30 book
PostPosted: Apr Fri 03, 2020 12:40 pm 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 481
Tubologic wrote:
Really a very ambitious project ! I guess it can be done but the real challenge would be collecting all the necessary original RCA special parts... 47 years later !


I was standard practice at one point at least for RCA to provide entire RF coil kits for TV's , I have one sitting in front of me on my desk. I took a couple of items out of the boxes for the photo. These have everything required by the home constructor except the Yoke, Lopt and frame output transformer and the two typical blocking osc transformers.

RCA were very good with documentation and sharing their research information too. I have all of RCA's wartime research papers that led to the development of deflection scanning systems & FM sound etc. In their deflection department, Otto Schade was their chief investigator and produced very impressive theoretical & practical work.

Speaking of something being on my desk, it reminds me of a story that might cheer a few people up in these darker times, but the mods might delete it, if its not funny enough:

A pathologist was being questioned on the stand in a courtroom. The lawyer said to him; now you certified that Mr. Brown was deceased, but what steps did you take to ensure that was the case, did you check his pulse ? No, replied the Pathologist. Lawyer; did you check if Mr. Brown was breathing ? No, replied the Pathologist. Then the Lawyer said; well if you did not check Mr. Brown's vital signs, then how could you be sure that he was in fact deceased ? The Pathologist replied; Because his brain was in a jar on my desk.
The Lawyer became exasperated and replied; Notwithstanding the fact that some, or all, of Mr Brown's brain was in a jar on your desk, is there any possibility that Mr. Brown could still have been alive ? The Pathologist replied, Yes, he could be alive and well and practising Law.


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