If the Italians can restore DaVinci's Last Supper fresco in Milan and justify it, this box o' bulbs can get the same. Go for it. The intellectual and historic end result is seeing the intent and accuracy of the artists work...not how it got there. Think of the glowing phosphors as the canvas of the fresco and the restored, tinted plaster as the chassis.

I think intent on the part of the inventors/designers applies here. Just think of how many changes they made to this particular chassis to get what they wanted. It was not a one and done effort. And there is no hope of picking one particular version of this set. They were all failures until it worked. It was an ongoing process to get the CRT to glow in color and that should be the same here and stop at that point.

I for one have to agree, especially since I have seen said fresco in person :smoke:

If this is going to happen, Pete and Bob will stop by on Sat and we'll see what the result is. My hope is that we will all see what RCA had in store for the viewing public back in 1952-ish!



Agreed, though there should be one caveat: the developmental chassis was an experiment in what was to be, insomuchas color chassis go. Let's not make any assumtions on what was TO COME, based on what we already know. That would be a mistake. Every evolutionary step beyond what I currently own is still a grand mystery. Nothing is written in stone. That said, I eagerly await the results of a developmental CRT powered by a production CTC-2 chassis. Much fanfare waiting in the wings!

This is really, really exciting. :yes:

Interesting thing about this chassis is it may not have ever worked, at least not in the fashion we have come to expect from a Color TV.
You may get green people and orange skies for all we know, maybe it won't produce any kind of stable colors at all.

Maybe red apples, green grapes and blue bananas. :)

Actually it all poses a question ..if it was an experimental chassis... one designed to have changes and additions made as RCA made changes to its dot sequential system.... just which version do you restore the set to match?

But this whole exercise is one of the most exciting on this forum ever!

Throwing in my two cents; I'd restore it the way you plan on doing it, if the CRT is actually good. If it were bad, I'd have to think hard before having the CRT rebuilt. As Eric said, we don't know how functional the chassis ever was. But, it would be fun to find out.

John

Well, we don't have to wonder anymore!
 

:banana::banana::banana::banana:


IT WORKS!!!!



:banana::banana::banana::banana:


Bob and Pete stopped by today with a CTC-2 chassis, wooden CRT truck, extension cables, CRT testers (to read all the guns at one time), and of course a Wiz of Oz DVD in tow. One more test of the tube with Bob's Beltron proved that all 3 guns were indeed working perfectly, so we set about powering it in a real world situation with Pete's CTC-2. The CRT was placed in the truck, cleaned, yoke and purity assemblies installed, and Bob's anode extension wire attached. We connected my DVD player to the CTC-2 using Pete's composite input mod box, and powered the chassis through my RCA Isotap variable isolation transformer set to 115 VAC.

We threw the switch, HV spooled up, and got a bright full raster! There were a few hiccups getting an actual picture to appear which were mainly my fault for powering the DVD player incorrectly, but in the end we were able to get something on the screen. Something was amiss with the Merrill though, as it was only powering one gun at a time and so we were not able to do any convergence or get a color picture. Just proving the tube still works was a monumental success for the comminuty, and so we called it a day.

Enjoy the pictures!

Setting up the CRT for testing.

http://videokarma.org/attachment.php...7&d=1308454284

Historic first light!

http://videokarma.org/attachment.php...8&d=1308454284

Initial images being displayed. It's supposed to be the yellow brick road, but degaussing, purity, and convergence all still need to be done before anything decent appears on this tube.

http://videokarma.org/attachment.php...9&d=1308454284
http://videokarma.org/attachment.php...0&d=1308454284
http://videokarma.org/attachment.php...1&d=1308454284

What incredible news! :banana::banana::banana::banana::banana::banana:

Congratulations!
jr

Oh guys ..this just so amazing ..what a find ..now you can really set out on that Yellow Brick Road... where this journey will end is anyone's guess!!

As far as convergence & purity are concerned, are you sure that the CTC-2 chassis and this developmental CRT are fully compatible with each other?

Wow, an almost 60 year old prototype CRT in pristine condiition actually working! It will really be something if the chassis can be made operational and get a picture. Congratulations! I wonder if the prototypes used the same phosphors as the CT100's.

Yes, if they were not we would not have had a decent monochrome picture on the screen. The electron gun is almost identical to a 15GP22, the pins are all the same. At this point we were not able to get color because of a chassis fault, and even if the chassis was 100% the tube needed to be degaussed and we didn't have the degausser. Therefore, we could not do any of the setup operations which would be required for proper display. A project for another day.

RCA may have dropped the ball by going with the leak prone 15G, this design seems more robust.
I wonder what their reasons were, perhaps we'll find out.

Eric H, I don't think so. I have four (4) metal bell prototype color CRTs, and they are ALL down to air, and I know of several others that are also down to air. So this is the only one still under vacuum. Certainly no better than the 15GP22, and probably worse, though the data sample is rather small, hard to draw meaningful statistical conclusions.

This is fascinating, to see that early CRT working. Is it a metal-cone design? Can any of you see possible places where leakage could happen (on this tube, or the other prototypes)?

If you're going to draw statistical conclusions from the types of envelopes used, it would seem more accurate to include such tubes as the 12UP4, 16GP4, 19AP4, and 21AXP22 since it's basically the same thing as this one contruction wise. So far as I know, the 15GP22 was the only one to use that infamous flange seal. *EDIT: actually I think the CBS 205 and Westinghouse tubes used a similar design.*

Now I'm not saying that welding the CRT together was a particularly good idea no matter how it's done, but it seems to me that there are probably more operational tubes with the prototype's kind of construction than there are operational 15GP22's though there were also more of the B&W ones made.

Yabba-dabba-doo! I was hoping to see pictures.

Phil Nelson

Possible Leaks in Metal Cone portotype color CRTs

1. Evacuation seal (copper pinch off type)
2. Wire to glass seals at base (not very likely)
3. Glass to metal seal at faceplate of tube
4. Glass to metal seal between neck and rear of metal funnel
5. 8 welded bolt heads which protrude through sides of metal bell, part of the phosphor dot plate and shadow mask mounting assembly
6. Metal to metal weld between front and back of metal funnel (similar to 21AXP22)

Summary: Lots of places for these tubes to leak!

I had the honor of seeing this historic event in person. I just happened to be there today to purchase some sets, and stayed to see if the prototype CRT would light. I figured I was going to miss the power up of the CRT so I did not bring my camera, but got some shots on the cell phone. If I can figure out how to get them off of the phone I'll post them, and email them to miniman82 as promised. I wish I had the presence of mind to bring my degaussing coil.
I even got some pictures of the set with the green beter converged than on the first moments of it displaying video.

This is definitly the most historic TV related event I've ever attended, and perhaps the most historic event I'll ever attend!!!

What an amazing experience to be among the few to see perhaps the only working original prototype shadowmask color tube display picture for the first time in several decades!

I'm still amazed that I got to see that in person!

Tom C.

Now this has me worried. The picture on the 21AXP22 in my Admiral 29Z1 (C322C16) was pretty dim years ago. I stupidly tried flashing the cathode, but that made no difference. I'm now wondering if the tube was indeed going soft. It needs a few tubes put back in and capacitor replacements before I can try it again. If the sulfide tube IS shot at least I have a NIB 21FJP22 to replace it with.. but those rich reds will be gone.

I had a 1981 Sony XBR in which the picture tube went completely to air after 8 years. At $700 in 1990 dollars for a replacement that was the end of it.

This is a fascinaitng thread. Thank You.

My experience is that the 21AXP22 is much less likely to leak. We have 8 tubes, either in sets or in boxes, and none have leaked. You'd never have that luck with 15Gs.

Good, that encourages me to get this set going again, thank you. :banana:

The heavy duty (D550?) Weller soldering guns double very effectively as a degaussing coil.
Try it, you'll be amazed.

We tried my my antique Weller 145/220 watt, it didn't do anything at all. I'll get my degaussing coil back from Mark sooner or later, don't worry.

Roger that. This thing's got a Lost Ark mystique about it, in spades. oc

It's Pete Deksnis here at Bob and Tamy's house for an overnight visit. Mal, it's a good question and I believe based only on physical shape, the two are not compatible. As to adjustments for purity are concerned, no, I wasn't about to shift that CT-100 yoke back and forth along the neck with 20 kV 1/2-in. from my hand. I did rotate the purity coil and it did affect the picture somewhat, but this was not the time for perfection... too many variables at play.

My CTC2 had been powered up for the first time yesterday since breaking down the RACS 15GP22 rebuild demo at ETF on May 1; since then it traveled over 1500 miles in the back of my Yaris, so I was very glad to see the HV still working (including the ozone if you were there seeing and smelling it operating at ETF!) and only the green channel not operational.

Glad to have been able to inspect the proto chassis up close; still many, many questions to resolve. Nick and Bob found a socket for a crystal, but there's no positive indication that it is for 3.579595 mc.

What a great opportunity we few had to participate in and witnesss such an historic event.

Pete

First-Light 1952>>2011
 

Fantastic work Nick, Pete, and Bob! I'm really glad you guys were able to get to "First-Light 2011" in such a short period of time.

Correct. I was speaking more to the electrical compatability between the 2, and they seem to be a perfect match. Bob noted that the gun was almost identical to a production 15GP22 one, only a few added supports differ between them.

Wouldn't it be nice if you could lay hands on the engineering notes for your prototype? Delay line questions, burst frequency, convergence supply specifications, how and if high voltage is regulated, what tubes go where, the list seems endless.
It looks as if this thread could last a while. That's perfectly fine by me.:yes:

My guess is that all these questions will be answered by our color experts as Nick traces the circuits.

Yes, the schematic is the thing.

Posible CPA Set
 

To the Color Gang,

Nick and I have just had a wonderful 1 1/2 hours on the phone tracing his chassis circuits from the CRT grids back through the 6BL7 color crt drivers,and 6AS6 demodulators. We had discussed the evolution of NTSC standards, back through the Feb. 2, 1953 NTSC Field Test Specification, and further back to the initial definition of the NTSC field test standard published on November 26, 1951. See http://novia.net/~ereitan/NTSC_overview.html

This November 26, 1951 standard used quadrature modulation of 1 MHz. B-Y and R-Y color difference signals, CPA (Color Phase Alteration), a 3.898125 MHz. subcarrier, and reference burst on a pedestal on the back porch of horizontal blanking. . In doing our tracing Nick discovered a transformer labeled "CPA".

Our initial conclusion is that it is a chassis probably used during the CPA Field Testing during 1952. There were several manufacturers who built field test receivers during that period.

We have yet found nothing to confirm that it was built by RCA or by any other manufacturer.

The chassis may have been modified from CPA up to the later NTSC Feb. 2, 1953 standard. We will see.

Further tracing of the circuit and documenting the circuits will be don.

Ed Reitan

Very interesting indeed!

Thank you Ed for the revealing and informative conversation, the amount of information that the early color crowd is providing is astounding to say the least. The collective knowledge shared here cannot be found anywhere else on planet Earth, of that much I am certain and I am forever grateful!

As Ed indicated, we started out following the wires though the various components connecting each stage to the previous one. I was poking around in an area that I had assumed would have something to do with demodulation, positioned in the circuit just prior to the 6BL7 grid driver tubes, and containing 6AS6 tubes. That's when I struck gold: Hidden under some passive components was a chassis stamp in black ink right under a tall transformer, which reads CPA.

http://videokarma.org/attachment.php...4&d=1308519977

It's a pretty tall can, so I was curious what it had inside. Taking much care not to damage or disturb anything, I slowly removed the nuts holding it to the chassis and this is what's inside. It's only about half the total height of the can, and appears to be some sort of transformer. I cannot see any kind of slug in the center of it, so I'm assuming it's an air core non-adjustable type.

http://videokarma.org/attachment.php...5&d=1308520089
http://videokarma.org/attachment.php...6&d=1308520089
http://videokarma.org/attachment.php...7&d=1308520089

From Pete Deksnis @ Bob's place: I had the same thought; but I suspect the transformation was not completed; hopefully so, as it would simplify the reverse engineering.

Pete

Nick... Amazing set!

Wow! This is all very fascinating, will be watching this thread with great interest...:yes:

This get's more interesting by the day! Probably one of the most interesting things that's happened here yet.

The genesis of Color TV being uncovered before our eyes, it's one thing to read about field tests and demonstrations for the FCC, quite another thing to see the actual hardware rediscovered and brought to life.

It's only been 60 years since this was being created but so much seems to have been lost.

I suppose it's lucky there's as much written documentation as there is, I wish there was a few hundred hours of period Technicolor footage to go with it.

They must have filmed some of their tests??

To go back in time with a HD Flip Camera hidden in my pocket.

Do you guys know if this set was EVER actually fully functional ?