Prototype set is here - Page 21 - Videokarma.org TV - Video

zenith2134 · #1 01-28-2012, 08:47 PM

I've got a '99ish Handycam (NTSC) and regularly record screen shots off of CRT with it... The key, in my experience, is to adjust the exposure accordingly with program content. Also, focus is critical if you are doing 'experimentation'....the slightest focus adjustment in some cases makes all the difference---between perfection or total runaway-into-obliviion of your shot...

miniman82 · #2 01-11-2012, 08:30 PM

Well, that saves me some trouble. Thanks you, Darryl.

I don't know if it's just my computer, but it's having trouble playing the mp4 format very well. Click the link below, I encoded it to AVI format. It's half the size of the mp4, so it runs a little better.

http://miniman82.4t.com/images/proto...PandNW.mp4.AVI

miniman82 · #3 01-29-2012, 12:50 AM

Update: I have been unable to get assistance with digitizing the schematic information I have on paper for this chassis, so Steve McVoy has graciously volunteered to step in and do the work. I'll be mailing him a manila envelope on Monday. I hope he can get things squared away with it, because it still doesn't make any sense to me. lol

old_tv_nut · #4 01-29-2012, 02:10 PM

Quote:

Originally Posted by miniman82

Update: I have been unable to get assistance with digitizing the schematic information I have on paper for this chassis, so Steve McVoy has graciously volunteered to step in and do the work. I'll be mailing him a manila envelope on Monday. I hope he can get things squared away with it, because it still doesn't make any sense to me. lol

I didn't realize you were looking for help on scanning something - next time, ask me.

miniman82 · #5 01-29-2012, 03:02 PM

It's not scanning per se, what needs to happen is the information needs to be translated into a computerized schematic program. The symbols must be drawn, and all the wires connected. Some use a simple drawing program, but it's much easier if you have the right program like Steve does. Then is can be easily modified/emailed/reproduced as needed, and it will be a lot easier to read vice the 9 sheets of lined paper I have now.

old_tv_nut · #6 01-29-2012, 03:19 PM

Quote:

Originally Posted by miniman82

It's not scanning per se, what needs to happen is the information needs to be translated into a computerized schematic program. The symbols must be drawn, and all the wires connected. Some use a simple drawing program, but it's much easier if you have the right program like Steve does. Then is can be easily modified/emailed/reproduced as needed, and it will be a lot easier to read vice the 9 sheets of lined paper I have now.

Ah - gotcha. Thanks to Steve, then!

Steve McVoy · #7 02-01-2012, 09:15 AM

As Nick mentioned earlier, he has sent me has hand drawn schematics and I'm cleaning them up and digitizing them. I am almost finished with the IF/sound sections, and have found what may be some evidence that the set is from RCA. There are 4 video IF stages, and they are very similar to the design in the CT-100, other than the fact that there are 5 stages in the CT-100. It is possible that RCA IF transformers were used by another manufacturer, too. I will be posting this part of the schematic soon.

Steve McVoy · #8 02-02-2012, 01:12 PM

Preliminary schematic for the IF and audio sections have been published:

http://www.earlytelevision.org/rca_color_prototype.html

In doing the IF circuits I compared them to the Sams folder for the 1952 RCA 21T176. The prototype set is almost identical, even the use of a choke in the filament line to isolate some of the IF stages. This indicates to me that the prototype was most likely made by RCA.

http://www.earlytelevision.org/image...Sams-157-8.pdf

Steve McVoy · #9 02-11-2012, 05:17 PM

Much more has been learned about the RCA prototype color chassis. Here is the latest:

http://www.earlytelevision.org/rca_color_prototype.html

zenith2134 · #10 02-11-2012, 05:59 PM

Forgive me if this has been covered already, but where did you ever end up finding this set? Gotta be one in a million. Or much more.

Steve McVoy · #11 02-11-2012, 06:11 PM

Take a look at the link in the post above yours and you can read the story.

John Folsom · #12 02-11-2012, 06:51 PM

Nick, Steve Mcvoy, Ed, Terry and all, that is simply outstanding work putting together the schematic and research to match it up to the RCA patents. I am convinced that we now understand the pedigree of this unique engineering prototype, and look forward to seeing it at the ETF convention in May. :-)

Sandy G · #13 02-11-2012, 08:07 PM

Did you guys contact RCA (Yeah, I know...But still..) & try to get any help/guidance from them ?

zenith2134 · #14 02-11-2012, 09:31 PM

Ah, how'd I miss that.
Great read, by the way. I'm intrigued by the presence of those ecc82's in the possible CPA positions... still need to wrap my head around the whole CPA thing..but one thing's for sure-this is a superb, rare item.

miniman82 · #15 02-12-2012, 12:34 AM

Some info has come to light that I think needs to be shared:

There has been at length discussion behind closed doors among the 'early color' crowd as to the true nature of the chassis: who designed/built it, what transitions it has gone through, and what lies in its future.

Who designed/built it-

Steve McVoy, among others, has been doing some very good digging lately, and now feels confident calling this an RCA developmental chassis- I concur. The facts so far are:

1. Its tuner, IF and 1st video stage are all carbon copies of schematic drawings of other RCA sets from the same time period.

2. There is now patent evidence showing that RCA did in fact use the 6BL7 tube, even if it was only in an engineering drawing. Those circuits closely match what the prototype chassis has. Still no proof that these drawings were ever used, but it is encouraging to see evidence that it was at least considered.

3. Evidence has been found to support the idea that the chassis had been used at one point to explore the possibility of CPA (field rate), but was later abandoned. This can be proven by careful study of the color circuits, and by the fact that the tubes required for the implementation of CPA (a pair of 12AU7's for a field recognizer) are still in the chassis though not connected to anything (only the heaters remain connected). It also supports documentation of what was going on at RCA at that time, with the field tests and so forth being conducted in connection with the NTSC. What standard the chassis uses now has yet to be determined, since the color subcarrier frequency has not been nailed down. I am working on this at the moment, by attempting to use a frequency generator rigged through the subcarrier oscillator. I will read it's output, and determine which one it is best suited for.

4. No conclusive evidence has been found thus far to convince us that it was made by any other manufacture but RCA. There is too much evidence pointing to RCA at this point, which is why we are in agreement they are those ones who made it.

Transitions-

We now know that at some point the chassis had CPA circuits in it, what is not clear at this point is when that changed and what standard the chassis now uses. There are some anomalies in the color circuits that still have to be hashed out, but I have my suspicions that it was modified to the '53 spec using the 3.58mhz subcarrier.

The Future-

Still remaining is the mystery of why the horizontal section of an apparently RCA chassis uses a seemingly Hazeltine regulator design, which is a pulse regulator type, versus the later standard shunt-type scheme.

As to whether the chassis will ever work again: it will depend on what type of standard the set is found to operate on, and if the electronics are still good. My aim has always been to see what this chassis is capable of, but at some point a decision will have to be made on whether to make it CPA or not. This is still a long way off in the coming months/years. Also yet to be determined is how they managed to stuff a delay line into an IF can- John Folsom has in his possession a chassis with such a line, but it is not in a can- only small enough to fit into one. So it's possible the chassis opening marked 'DELAY' really did have a luma delay in it, but we can't say for certain just yet. It has been found that the video cathode follower has an open circuit where the delay line 'should' be, but it has apparently been removed. Why? Who can say, there is only speculation at this point.

There will be a demonstration of the prototype CRT at this years convention, with the tube mounted in a CT-100 cabinet and being driven by a Merrill chassis. I expect it will be an enlightening experience for all who see it, true history being revealed before our very eyes. The chassis will also be on display for all to ponder, the more eyes the better. I will give a presentation on what we currently know about the chassis, and expect there will be much discussion afterwards about what has been said.

So, we have learned a great deal here recently. Progress will proceed as fast as possible on the chassis, which will be shipped to Steve at the museum before the convention so he can study it in person. That's all I have for right now, more updates as they become available.