miniman82 I could use a single female one.

I could use a single female too.:naughty: :D

Seriously though my only spare female webcor connector is hidden away in one of my parts boxes and college has resumed for me so it could be a while before I mannage to find it. When I do locate it I'll contact you then drop it in the mail.

Tom C.

I could use a single female too. :naughty:

Call my geek brother, if that socially awkward MSOE alum can score so can you. :D

Wow! I just looked at this. Looks like you're gonna get that baby playing, again.... I remember it on ebay. Harry had a rare one there.
Wonder where he picked it up....
Bill Cahill

+1...would love to hear the history of this unit.

Said a picker brought it to his attention.

I have a question...
After seeing the original ads by RCA on the two model sets, and, seeing they used a cabinet similar to the BW sets, but, seeing differences, such as deeper cabinets, and, decal on topfront, instead of middle panel, why are you destroying a rare BW tv that I would dearly love to have to put this rare set into.? Seems it was in the original factory cabinet it came in.....
And, you want to change pix tube mounting from full chassis to part cabinet to make it fit? I know you believe in originality, and, accuracy. I've always admired your work. But, why ruine a BW set that I, for one, would love having to put the color chassis in? I think it's already in it's original case. And, even if not, it's certainly the same style it came in....
I'm even surprised RCA even advertised this set, showing they must have offered it for at least limited sale to the public. I would dare say the cost must have been so high that you can count the numbers left by a few digits, at best.
I fully support restoration of this set, and, seeing it playing, again. But, it seems it's in the closest to the original case now...
Bill Cahill

I am afraid I agree with Bill. The RCA TC-168 is a fairly rare set and it was one of the better designed RCA receivers. Also the 70 degree 16GP4 is shorter which means stuffing the prototype receiver into the cabinet with the CRT sticking so far out the rear is not the best solution.

I feel sad such a set is being sacrificed.

Terry

You're both making some pretty large assumptions...


After seeing the original ads by RCA on the two model sets, and, seeing they used a cabinet similar to the BW sets, but, seeing differences, such as deeper cabinets, and, decal on topfront, instead of middle panel, why are you destroying a rare BW tv that I would dearly love to have to put this rare set into? Seems it was in the original factory cabinet it came in.


RCA themselves used TC series cabinets to house the early color receivers, see the ETF site: http://www.earlytelevision.org/rca_color_prototype.html

If RCA used a TC-165, so I really don't see a problem using a TC-168 for this one. I wanted a 165 so it could be as close to the ETF pics as possible, but this one came up. The cabinet it came in was definitely NOT right for this chassis, it was not nearly deep enough to house the whole thing and it was in very poor condition anyway. Warped beyond repair, with bad veneer to boot. And RCA never put up 'ads' for these sets, they were company prototypes never offered for public sale.

you want to change pix tube mounting from full chassis to part cabinet to make it fit? I know you believe in originality, and, accuracy. I've always admired your work. But why ruin a BW set that I, for one, would love having to put the color chassis in?

I'm thinking about ways to make the chassis compatable with this cabinet, but haven't committed to anything just yet. If there is a way to keep the picture tube with the chassis, I will find it. It will likely involve new side supports, nothing major.

'Ruining' a B&W set? Pardon me for not having pity on a B&W set, when this ultra rare prototype needs a home. If you want to save it that badly, surely you won't have a problem buying it for $250 and having it shipped to your place? You could have bid on it while it was listed on Ebay, there was equal opportunity to save it there. I'm not being disrespectful with you, I simply fail to see the logic on this. As rare as a TC set is, I promise the rarity of the color set outweighs it.

I'm surprised RCA even advertised this set, showing they must have offered it for at least limited sale to the public. I would dare say the cost must have been so high that you can count the numbers left by a few digits, at best.

This is a PROTOTYPE CHASSIS. It was never offered for sale to the public, nor was it intended to be. There was no advertizing at all, only historical documents and pictures to show what RCA was up to back when color development was in its hayday. Same goes for the Model 1/2/3/4 and probably 5, though I've heard stories of the 5 being in store windows for the Rose Parade. Not sure if that means the stores bought them, or they were on loan from RCA. Ed Reitan probably knows, you might ask him.

I fully support restoration of this set, and, seeing it playing, again. But, it seems it's in the closest to the original case now.

I like the 168 cabinet. It's nice to look at and fits the chassis very well. There's another cabinet on it's way from Nashville right now, between the 2 I will make a decision on which one is more practical for the prototype.

I am afraid I agree with Bill. The RCA TC-168 is a fairly rare set and it was one of the better designed RCA receivers. Also the 70 degree 16GP4 is shorter which means stuffing the prototype receiver into the cabinet with the CRT sticking so far out the rear is not the best solution.

At 24 inches, it's one of the few cabinets that is deep enough to swallow the entire chassis, only a small portion of the CRT support and neck will be out of the case. I don't think RCA ever even made backs for the prototypes, at least I've never seen one. Being developmental, there was no pressure to make them look like production sets (from the back). That said, I will make a back for this one to protect it.

Perhaps the other cabinet will make a better choice? I won't know until it gets here, in the meantime I challenge you both to find a cabinet that fits this chassis while not sacrificing a 'rare' B&W set. I did the legwork to get this one here, if you know of a better one post it up. I'm in the Military and we have a saying: Don't bring up problems unless you have a solution in mind. If not, you're just complaining. Again, not being disrespectful. I'm just trying to get this thing in a decent cabinet, having bought 2 other sets already is putting a financial strain on the effort.

I have a 21" SC in a chinese painted cabinet that would work better, and, changes could be made to that.
It's certainly deep enough.
I didn't know the ads were meant only for FCC until I saw it after post.
250 Is a bit rich, plus shipping, as you certainly didn't pay that much. I didn't know it was on ebay, or, I just may have tried to save it.
I really like that set, and, wish I could find such a nice one.
I'm not knocking your prototype. INdeed, I'm fully supportive of you getting it going again.
But, first, what is the real problem with saving the case it's in?
If worse comes to worse, I have a 1951 RCA 17" mtetal tube with full doors , and, a nice curved front that I'm not in love with. Wanna trade?

Please don't get so upset. I was just trying to ask if there was something better you could use.
I love color, and, admire that prototype alot, but, I also like BW. I know of relative rarity of the one you might use, and, wish I had it. I love the style, and, obviously, the condition isn't half bad, either.
Bill Cahill
By the way, the cabinet you have that it came in isn't a TC-168. It's a 6T64 using the cheap KCS 47 chassis.

I suppose there's even the possibility that this prototype was never mounted in a cabinet. Someone mentioned there were no bolt holes. Are there any signs, that it was at some point mounted? I'm guessing it spent most of it's experimental life on a test bench.

Now, that's a possibility I haven't thought of. Are there even any mounting brackets on the chassis? If not, perhaps moutiing it on a board with a finnished front might be better?
Bill Cahill

RCA themselves used TC series cabinets to house the early color receivers, see the ETF site: http://www.earlytelevision.org/rca_color_prototype.html

If RCA used a TC-165, so I really don't see a problem using a TC-168 for this one. I wanted a 165 so it could be as close to the ETF pics as possible, but this one came up.

About a year ago, I was trying to buy a TC-165 off ebay. The deal fell amicably apart due to the delivery. He is in Milwaukee, too far away for me. I think his TC-165 would be a good candidate.

The fellow's name is Tom and his email address is <[email protected]>. As I said, this was a year or so ago but he said the set was in a shed and he sounded like a reasonable guy.

Terry

I have a 21" SC in a Chinese painted cabinet that would work better, and, changes could be made to that. It's certainly deep enough.


SC is not RCA and being 21", it's certainly a square set that would require extensive mods. Not a good choice, the whole front panel would have to be fabricated from scratch. Plus, I find the Chinese cabinets repulsive. This set was home grown in the USA, I'd like to keep it looking like it was.

250 Is a bit rich, plus shipping, as you certainly didn't pay that much. I didn't know it was on ebay, or I just may have tried to save it.


What the hell do you know about what I paid for this set? Bill with all due respect you have no place to tell me what's high or low here, or make speculations on what's fair. I know what I paid and believe me, selling it at $250 would be taking a loss. To want to save this is one thing, but then to come in here and tell me what's fair is a little beyond me. You'll just have to find another one.

I really like that set, and, wish I could find such a nice one.


Then I respectfully suggest that you keep watching Ebay and CL as I did and find your own, or wait and see if I don't end up needing this one. Bantering back and forth with me on this is pointless, until I make my decision.


I'm not knocking your prototype. Indeed, I'm fully supportive of you getting it going again. But, first, what is the real problem with saving the case it's in?

What case? The case it's in is the TC-168. The one it was shipped in was far beyond repair, I tossed it a long time ago.

If worse comes to worse, I have a 1951 RCA 17" metal tube with full doors , and, a nice curved front that I'm not in love with. Wanna trade?


I'm not interested in spending more money on a cabinet I may or may not use, wait and see what I decide. If I don't need the 168, you can PM me and we'll haggle.

Please don't get so upset. I was just trying to ask if there was something better you could use.


Who is upset? I will choose what I choose, it's my decision. If I don't end up with the 168, it will be in the classifieds. Again, I don't much care what B&W set this used to be. There were far more TC sets made than field test sets, I have no reservations about using this cabinet. I could see if it was a 621 or something, but as far as I'm concerned it's no different than any other 50's 16" set.


Kevin: There are no mounting tabs on the chassis, but that doesn't mean it wasn't in a cabinet. Again, we don't know what RCA did to the other prototypes. Maybe none of them had tabs.

I suppose there's even the possibility that this prototype was never mounted in a cabinet. Someone mentioned there were no bolt holes. Are there any signs, that it was at some point mounted? I'm guessing it spent most of it's experimental life on a test bench.

I have no direct knowledge on these early color prototypes, but as a general observation lab prototypes are considerably different from field test sets. Field test sets like my RR359's were built more like production units since they were placed in peoples houses and had to be robust. There were also 100 of them built, so they needed to be assembled more like a regular production unit. There are little differences in build quality between them and production units.
Lab prototypes like this set that were never meant to be taken outside the lab, built on the order of 1, 2 or 3 units, and not operated by anyone but engineers usually lack the build quality of field test sets. I have a prototype pre-war GE set that has no mounting flanges on the chassis or mounting holes in the cabinet, nor any evidence that it ever had a back. This was probably done as the engineers would have never bothered bolting the chassis in anyway, so why bother. They were typically housed in decent cabinets so they could take the "glamour" shots to be used when documenting and displaying the sets to licensees and the FCC.

Just my 2 cents.
Darryl

What you really need is an empty CT-100 cabinet, should be one floating around somewhere. The price would probably buy a dozen B&W consoles though. :yes:

I do have one on the way...

I can see borrowing the cabinet of your complete CT-100 for a temporary place to put the proto type, but the CT-100 is one of those sets that like the 621 deserves to be preserved and restored IMHO.

Nick, if you paid 250$ on that monochrome set for the cabinet and less than half of that was for shipping, then A.) you wanted it real quick realy bad, or B.) you really let your self get fleeced. The most I've ever spent on a set was 120$ the two sets hold that most expensive distinction are my restored-by-the-previous-owner, Damn cool looking 59' Zenith, and the Silvertone roundy. RCAs of that era are still readily obtainable for nearly free on craigs list, etc for little or nothing if one is patient.

Sets like the cabinet donor I'd only be tempted to spend more than 50$ back when I was stronger into mono if they had been restored, of were ultra-mint.

Tom C.

I feel like I'm beating a dead horse here, but if you all must know the set was $110 shipping was $200. Want it bad enough? That's what you'll pay for it, otherwise I'd prefer if this wasn't discussed again till I have made my decision. The 19" set will be here later tonight, so I'll have a better idea of to do.

Not that im in any position to talk, other than having read the whole thread here, but how did it go from a legit thread about a 1 off prototype set, to flaming Nick over a freaking cabinet choise for the thing to be displayed in? Its not like he's chopping it up in pieces or puttinbg a damn fishtank in it!?
Everyone has their opinion and thats what makes this forum great, but i think were diluting the thread more than we should with the logistics of which cabinet, how much, which is rarer... i agree with Nick's beating a dead horse, back to the topic at hand i say...

With that in mind...


The 9-T-79 showed up tonight, and she's a beauty! Cabinet is just as nice as I thought it would be based on the pictures, only a chip or 2 of missing veneer by the feet which is about typical. Couldn't get pics of it in the darkness, but by the headlights of the car I yanked the chassis and picture tube. Chassis is nice and clean, a few tube replacements but the horizontal output and rectifier look original. Picture tube is an RCA Service Co. 19AP4D rebuild, which tests at the top of the scale with only 4.5 volts on the heaters. Life test doesn't even move the needle. :smoke: Must not have been run long after it was installed, the whole thing looks to have been mothballed just after the CRT was replaced. Lady said it still worked, but I'm not gonna try it.

Metal tubes FTW! :thmbsp:

http://videokarma.org/attachment.php?attachmentid=171699&d=1316662435

Tomorrow I'll get some cabinet pics up, then try to fit the proto chassis inside and take some measurements. It looks like it will fit, but I don't think it will make a good choice since the CRT is so much larger than the developmental one. It may mean some fooling around with mounting, we'll see tomorrow at the buttcrack of dawn.

Tomorrow I'll get some cabinet pics up, then try to fit the proto chassis inside and take some measurements. It looks like it will fit, but I don't think it will make a good choice since the CRT is so much larger than the developmental one. It may mean some fooling around with mounting, we'll see tomorrow at the buttcrack of dawn.

Just curious but were you not interested in following up the TC-165? Especially as it is so close to you?

I may look into it, but first I have to figure our which cabinet makes the most sense.

Here's the 9-T-79, pretty isn't it? Finish is almost perfect, I almost want to get it working as a B&W set and leave it alone...

http://videokarma.org/attachment.php?attachmentid=171704&d=1316737691

http://videokarma.org/attachment.php?attachmentid=171705&d=1316737691


The options I can see with CRT mounting on this cabinet are:

Remove 19" mask, mount 16" one on a piece of plywood, paint the same off-white color, then install into the cabinet.

Create wooden mounting for CRT, install in cabinet.

Somehow modify 19" mask to accept 16" tube.

Nick,
That is one awesome looking cabinet, I would say that it would make for an awesome way to display the prototype set. Im glad you are so dedicated to bring it back to life. Maybe it will be good in time for next years ETF and you could bring it and talk about it :)

Keep up the great work,

Matt

Here's the 9-T-79, pretty isn't it? Finish is almost perfect, I almost want to get it working as a B&W set and leave it alone. . . .

The options I can see with CRT mounting on this cabinet are: . . . . .

Somehow modify 19" mask to accept 16" tube.



I think you can have it both ways:

Do no damage to the B&W cabinet.

If you still have the CRT bracket that was on this set when Harry Poster had it:

http://earlytelevision.org/images/RCA-Model-1-poster-1.jpg

Since the prototype apparently has no mounting brackets, simply slide it into the cabinet with the original 19 B&W inch mask in place (or possibly a reproduction mask not so thick. You might have to fabricate a removable wooden "shelf" to raise the chassis to match the apparently higher positioned CRT in the B&W cabinet.)

It is my theory that the RCA prototype cabinets were made with oversize masks to accommodate multiple test chassis, and the front support bracket on the chassis was actually designed to be visible.

I know it is risky to assume color from a B&W photograph, but look closely at this B&W photo of an RCA color prototype from nearly the same era as your monitor:

http://earlytelevision.org/images/RCA_model3_front.jpg

Or this earlier color photo with the front of the TV is in deep shadow. Note the apparent double masks:

http://earlytelevision.org/images/1950rca16inproto.jpg

Or this RCA prototype, which is labeled a converter, but looks like it has a tuner:

http://www.earlytelevision.org/images/RCA_Converter1.jpg

James

It is my theory that the RCA prototype cabinets were made with oversize masks.

Not likely. RCA was always using parts from current stock, even when they designed the prototype colors tubes. The mask that came with the chassis is just a run of the mill 16GP4 mask, which makes sense since I've heard they simply modified a metal shell B&W tube with color guts. Indeed, the mask it came with is identical to the one in the TC168.

I'd keep the tube mounted to the chassis as it was, leave the cabinet the same, and make an inner mask to go behind the 19" one in the cabinet and keep most or all the front chassis CRT support out of sight. This would keep both the chassis and cabinet virtually unmodified so if a cabbinet you like better becomes avalible etc. you can put every thing back as it was easily and not have to (un)modify the proto set at all.

Double, triple or even quadruple masks don't bug me (they can even look awesome IMO in some cases) at all as long as they are executed well, and one can argue that 15GP22 sets were at least visually like that due to the mask in the tube.

Just thinking out loud.

Tom C.

Had some spare time today, so I made a new label for the proto CRT. The old one was ripped, so I found a picture of one on the web and inserted the part and serial numbers on to it. I carefully removed the old one with a razor blade, then applied the new one with clear tape. In case it gets melted, I put another larger one on the bell.

http://videokarma.org/attachment.php?attachmentid=171721&d=1316981476

That was a great job of making the replacement label!

Began work on the power supply, it was on hold today till the Packers got done whooping on Duh Bears. Go Pack, Go! :D

Below you can see the setup for reforming the NOS capacitors I got from Bob G, he had a drawer full so I was able to select the best suited ones. It consists of the power tranformers, rectifiers, a current meter between the cap and rectifier and a VTVM at the cap. This way I can measure the current the cap is drawing as it reforms, and the potential at the cap to make sure I do not exceed rated voltage. I got some nice tall unused cans from Bob: one with 80uf @ 475VDC and 160uf @ 250VDC sections, the other with 80/30/4uf @ 475VDC and 500uf @ 35VDC sections. There are 2 others that were used pulls, if I need those I will likely restuff them with new ones I have laying around. These unused caps are forming up very nicely, neither one pulled more than 1ma during the forming process and stayed cool as a cucumber. Real test is if I am able to apply full rated voltage right away tomorrow morning, if they hold that I will call them good to use.

http://videokarma.org/attachment.php?attachmentid=171723&d=1317014141

The power supply is being built pretty much the same as any other RCA one with a pair of 5U4G's, 80uf cap input filter, choke, then another 80uf cap (inductive pi filter). That's where 385VDC B+ will come from. Then there will be whatever resistor value is required to get a 285 volt rail, followed by another filter section. If I need another lower voltage rail, it will just be another resistor and cap. Tomorrow after work, I will likely build up the harness to go between the supply and main chassis. It's very tempting at that point to power up the tuner and IF sections of the proto chassis, just to see if an RF input signal will pass to the detector. If I do try and it does go through, I will then move on to the other circuits and see what they do. I know most people don't like the 'brute force' method, but it's the fastest way to figure out the relative health of circuits. With tubes you're not as likely to blow something as with transistors, so I don't anticipate any fireworks. Hopefully I can get a staircase to show up at the detector, it would be a very good first sign.

Most improtant update so far, besides the CRT still being under vacuum: the proto chassis passed it's first signal tonight!

http://videokarma.org/attachment.php?attachmentid=171738&d=1317189082

Yes it was a hacked together mess, no it was not pretty. But it did the trick!

http://videokarma.org/attachment.php?attachmentid=171737&d=1317189082

I cobbled together the B+ supply, powered only the filaments of the tuner and IF, then slowly increased the variac till 200 volts showed on the meter. Then I glanced over at the scope, and what do I see? A messy luma staircase at the grid of the 1st video tube! It looks like hell, but the important thing is it's there. There was no AGC voltage applied, so that's probably why the signal was all dirty.

Work today sucked, but this more than makes up for it. :thmbsp:

Tomorrow I figure I'll try to add some AGC voltage since I know where the AGC buss is located, to see if I can't get the signal to look better. Hope it works.

Nick,

Thats great to see some for of life out of that set :)

Keep it up man, doing a great job, with how it is going I fully EXPECT to see this at next year's EFT running off of one of Darryl's converters.

Matt

Great to see historically important circuitry come to life. Interesting photo too -- a CTC2 chassis lurking there behind the proto chassis.

That's what I call a professionally decorated room. I would feel at home there! Glad the critter is opening it's eyes! My dining room table is used more as a repair bench than a dinner table!

Glad to see that chassis still has some life!

Another historic moment indede.

My back is killing me; just looking at these photos. We need to pitch in and build Nick a double-wide work bench.

Working on the floor ain't the worst. I've never had a bench and am fine with that, though I'm still young and can take it.

Working on the floor ain't the worst. I've never had a bench and am fine with that, though I'm still young and can take it.

I did enough of it when I did in-home TV service. Also as an industrial electrician. I have right now, which they refer to as "electrician's knees."

Doesn't really hurt much, I'm used to lounging around the (Navy) ship on whatever is available. I once fell asleep on top of a aircraft fuel tank that was sitting sround on the flight deck...Believe me, it could be worse. Once I sell the CTC-7, I'll have more room in the spare berdoom to fool around so this stuff will likely get moved in there.

Ya could always banish the 7 to the garage and set up shop in the spare room if the project in the living room annoys your gal.

It gets better...wait for it....

http://videokarma.org/attachment.php?attachmentid=171749&d=1317268945

Now I find it has a horizontal waveform going to the grid of the 6CD6, and I can hear the vertical section working too. Both vert and horizontal hold controls work as advertized, anyone dare me to stick the output tube in? :nono:

Yes, I DOUBLE DARE you.

Wow, very nice!

I'd imagine flys for the prototype are super-unobtainium so I dare you to make sure (double or triple check) all is right with the horizontal before puting in the output tube and meter the cathode current on the first power up. With how unique this set is it would be somewhat tragic to get over zealous and cook the fly.

It is exciting to see progress on the electronics.

Tom C.

I'm on tender hooks now! :yes: To see this prototype set being woken up in sections from its long slumber is quite something. Yeah I dare you to stick the flyback tubes in there too :D..No seriously, don't until the time is right. :) Cheers

Very slick, Nick!

I can't tell-have you replaced or restuffed all of the paper and electrolytic caps on this chassis? If not, I would be afraid of powering up the horizontal output tube.

Very slick, Nick!

I can't tell-have you replaced or restuffed all of the paper and electrolytic caps on this chassis? If not, I would be afraid of powering up the horizontal output tube.

Second that. Also, make sure the H oscillator frequency is right before running the whole system. Possibly having it sputter because it's too far off (or just having it free-run at a low frequency) would be hard on the output and flyback.

I think Harry was watching this one well into the 90's, he just didn't want to spoil the fun. ;)

You are doing a great job on this set. I'm excited to see the results.
Bill Cahill

Quick question: this chassis has a control labeled 'Horiz Phase'. Anyone have any idea what the purpose of this control might be? It's a pot connected at one end to the cathode of the horiz output tube which sits at around 25 VDC, other end appears to go to pin 5 (grid) of the 6BQ6 (pulse reg?). Wiper is connected to the cathode circuit of a 12AT7 tube, which I'm assuming has to do with HV regulation since it takes an error voltage from an external winding on the horizontal output transformer, and also has a connection through a plate cap to the grid of the 6BQ6.

Scratch that. Reading from the plate cap of the horizontal output tube to the cap of the HV rectifier shows infinite resistance, where I would expect to see less than 500 ohms. Looks like the horizontal output tranformer is bad. :tears:

Nick, examine the HV winding on the flyback carefully. Often the failure is at one end or the other, where it might be possible to repair. Another option is I could wind you a new HV winding. Give me a shout if you want to discuss the possibilities.

could it be a transformer and not an autoformer?

Nick, examine the HV winding on the flyback carefully. Often the failure is at one end or the other, where it might be possible to repair. Another option is I could wind you a new HV winding. Give me a shout if you want to discuss the possibilities.
Now there's an offer that Nick isn't likely to take a pass on. I'm very impressed to consider that the HV winding can be fabricated and replaced.
I'm standing by to follow this saga.
John, photos would sure be a treat for everyone.

Quick question: this chassis has a control labeled 'Horiz Phase'. Anyone have any idea what the purpose of this control might be?
It could be literally what it says, which on many monitors I have used is essentially a horizontal centering control. Its function would be to center/position the video within the horizontally-scanned area on the CRT.

From your description of the circuit, this second possibility seems less likely, but if this is indeed a CPA chassis, could the phase control function as a tint/hue control?

If it's CPA, there would be no need for a hue control since the CPA was meant to cancel out color phasing errors. It might be something to do with centering the video in the frame, but it has a proper centering control to center the actual scan so I'm not sure what to think at this point. If Ed would get off his duff and email me those scans I might have a clue...lol

Phase if horizontal could refer to burst timing

Sent from my LS670 using Tapatalk

I guess you already have enough cabinet choices, but I thought of your prototype when this popped up on the local CL, as its grille resembles the CT-100 cabinet. It's much too shallow, however -- lacks about 6 inches.

Phil Nelson

If it's CPA, there would be no need for a hue control since the CPA was meant to cancel out color phasing errors.

CPA works at the vertical rate, not horizontal. One field is one color phase and the second field is the other color phase. CPA was dropped because in it's simple form it produced bad flicker at the vertical rate. There were no 'one field' video delay lines available to solve the problem at that time.

Cliff

CPA works at the vertical rate, not horizontal. One field is one color phase and the second field is the other color phase. CPA was dropped because in it's simple form it produced bad flicker at the vertical rate. There were no 'one field' video delay lines available to solve the problem at that time.

Cliff

Very true. The problem was that the NTSC system was not true constant-luminance because of the CRT non-linearity. (Current digital TV systems are not constant-luminance either.) What this means is that the chroma signal can affect the brightness of a color (more so for saturated colors, not at all for grays).

It's the chroma flicker translating into luminance changes that is visible. During the development of HDTV, Dr. Schreiber at MIT proposed going to a true constant luminance system, and demonstrated that 30 Hz true chroma-only flicker (or even 15 Hz!) is invisible. This could hypothetically be used to reduce the frame rate of chroma to save bandwidth, but would run into problems when the camera pans or the eye tracks a moving object. It also could be used to more crudely encode the chroma without producing visible artifacts.

Finally got around to making a base cover for the HV rectifier, now maybe it won't break so often from bouncing around. :thmbsp: It's just a section of poly that I cut from the center of an old wire spool, I was gonna use a pill bottle but couldn't find one the right diameter.

http://videokarma.org/attachment.php?attachmentid=171937&d=1319162399

Tom C. found the plug I need for the filament string in this chassis, I hope to have it in my possession by the end of the coming week. Now, if only I could source a backshell for the other plug...

http://www.videokarma.org/attachment.php?attachmentid=172290&d=1322423617

Tom C. found the plug I need for the filament string in this chassis, I hope to have it in my possession by the end of the coming week. Now, if only I could source a backshell for the other plug...

http://www.videokarma.org/attachment.php?attachmentid=172290&d=1322423617

What's the diameter of the connector? I may have a shell for it.

Cliff

What's the diameter of the connector? I may have a shell for it.

I get 1 3/8" for outer diameter, not sure what the shell size should be. Steve McVoy sent one from a regular octal connector, it was too small.

It's the chroma flicker translating into luminance changes that is visible. During the development of HDTV, Dr. Schreiber at MIT proposed going to a true constant luminance system, and demonstrated that 30 Hz true chroma-only flicker (or even 15 Hz!) is invisible. This could hypothetically be used to reduce the frame rate of chroma to save bandwidth, but would run into problems when the camera pans or the eye tracks a moving object. It also could be used to more crudely encode the chroma without producing visible artifacts.

The thought of true constant luminance is intriguing. Unfortunately, the benefit of transmission noise suppression in the blacks would be lost as the gama curve happily compensated for it. Not to mention the complication of adding a CRT compensation circuit at the receiver and having to reconcile some sort of backward compatibility if a fully constant luminance system was achieved.

With regards to the hue control critical adjustment, I recall working with "Simple PAL" receivers. The Delay PAL Monitors in the BBC studios had a simple PAL switch. It was great for checking PAL chroma subcarrier phase because an out-of-phase condition would yield "Hannover Bars". Each alternate line would have a noticable hue difference and even a slight phase misadjustment was very annoying. I would certainly prefer to see a noticable NTSC IQ system overall hue error to having to put up with the Hannover Bars. And this was the UK systems which allowed fully symmetrical upper and lower chroma sidebands which should eliminate the quadrature crosstalk problem! (Remember the UK channel was 8MHz wide with the sound carrier at 6MHz instead of 5.5MHz for their continental cousins. This allowed full +/- 1.5 MHz chroma bandwidth).

CPA was chosen as a means to help widen the chroma bandwidth (hence chroma resolution) and the Phase Alternate Line or Field was to help cancel the quadrature crosstalk resulting from the highly non-symmetrical chroma channels. Even with the hue control set to minimize the flickering, the flickering I would expect to be very noticable. In fact I would guess the hue control adjustment to be more critical for CPA than the later IQ system. It is which ever suits you: a slightly wrong overal hue versus a maddening flickery picture. (I, of course, use the term "hue" control loosely: it is the subcarrier phase adjustment I am referring to).

I get 1 3/8" for outer diameter, not sure what the shell size should be. Steve McVoy sent one from a regular octal connector, it was too small.

I misjudged what is in the picture entirely. Thought it was a small two pin 1/2 inch diameter Cinch-Jones connector, not something 1-3/8 inches diameter.

I'll look some more but I doubt there's anything like that in my parts boxes.

Cliff

I misjudged what is in the picture entirely. Thought it was a small two pin 1/2 inch diameter Cinch-Jones connector, not something 1-3/8 inches diameter.

The small one is coming with a backshell, it's just not shown in the picture. What I said was "Now, if only I could source a backshell for the other plug...", referring to the large 7-pin round one. No one seems to have one, so I may end up trying to make my own.

Has anyone considered construction of the CPA encoder? I wonder if an existing encoder chip can be modified for the purpose.

Ideally, it would be interesting to create as envisioned, a truly NTSC-CPA signal. Y', Cb', Cr', is available from many consumer devices and this would simplify the construction of the quadrature modulation and luma adder.

The R-Y axis would have to be inverted each field and the CPA sync would have to include the flag to properly correlate and signal the color field.

Any thoughts? It may be interesting to have an "official" competition to see who comes up with the best design. :scratch2: Maybe the prize could be, say, an RCA CTC-11 or something like that? :banana:

Has anyone considered construction of the CPA encoder? I wonder if an existing encoder chip can be modified for the purpose.

Ideally, it would be interesting to create as envisioned, a truly NTSC-CPA signal. Y', Cb', Cr', is available from many consumer devices and this would simplify the construction of the quadrature modulation and luma adder.

The R-Y axis would have to be inverted each field and the CPA sync would have to include the flag to properly correlate and signal the color field.

Any thoughts? It may be interesting to have an "official" competition to see who comes up with the best design. :scratch2: Maybe the prize could be, say, an RCA CTC-11 or something like that? :banana:

We were discussing this offline, and I thought had mentioned it on the thread, but perhaps not. If Nick decides to restore the set to CPA specs, I'll write the algorithms for my SCRF converters to generate the correct signal. Since the entire signal is generated in firmware, nearly any conceivable format can be realized. I have done other one-off or low volume versions like the British 405 NTSC, 405 SECAM and of course CBS field sequential color.

Darryl

We were discussing this offline, and I thought had mentioned it on the thread, but perhaps not. If Nick decides to restore the set to CPA specs, I'll write the algorithms for my SCRF converters to generate the correct signal.

I think it was only a topic via the email conversations. In any event, I still need to figure out which standard the set uses. To that end, I figured that getting the thing to actually run is the best way to do it. My brother is taking far too long to get the schematics in order, and I already have the horizontal section half ass working. Nevermind the fact that the schematics are causing their own set of issues, as far as being easily interpreted over the internet. Since the horizontal section is the heart of any receiver, it's a logical starting point. Once I have stable high voltage and sweep, I can hook up one of the CRT's and see if an NTSC signal does anything. I have a strong suspicion that it was modified at some point to use the later standard, but began life as a CPA platform- a test bed of sorts.

If it does turn out to be CPA, Darryl will definitely be getting a call from me. Rest assured, I will not stop until I am able to get some sort of picture out of this thing- hopefully a color one. :thmbsp:

We were discussing this offline, and I thought had mentioned it on the thread, but perhaps not. If Nick decides to restore the set to CPA specs, I'll write the algorithms for my SCRF converters to generate the correct signal. Since the entire signal is generated in firmware, nearly any conceivable format can be realized. I have done other one-off or low volume versions like the British 405 NTSC, 405 SECAM and of course CBS field sequential color.

Darryl

I suppose I can visualize an algorithm to rescale and interpolate at baseband spatially or temporally for example the CBS field sequential system, it blows my mind to think you would be able to accurately realize in firmware the correct relationship between the the baseband luma and properly interleaved chroma!

I thought an FPGA implementation would be a bit over the top in this case. I suppose I am old school still thinking of a firmly hardware based implementation. For component 525 video, no rescaling would be required and fairly basic hardware following early 50's guidelines (but in solid state) would have been most appropriate.

I suppose I can visualize an algorithm to rescale and interpolate at baseband spatially or temporally for example the CBS field sequential system, it blows my mind to think you would be able to accurately realize in firmware the correct relationship between the the baseband luma and properly interleaved chroma!


Modern video encoders use purely digital techniques to generate the composite signal. Writing the algorithms for my converters to do both quadrature modulation for NTSC/PAL and FM modulation for SECAM was relatively trivial. You can also add FIR/IIR filters for limiting the subcarrier bandwidth to the correct spec.

Implementing a discreet analog approach is certainly possible, but unless the source for the component video is coming from a very old piece of equipment, it's being sourced as digital data anyway, so it's just easier and cleaner to do all the work in the digital domain.

The great thing with fpga's is they can be thought of as equivalent to a software based solution but for hardware. You are still physically wiring low level hardware blocks together, but using firmware to do so, so you can change and add to the design ad infinitum without having to actually change physical parts or wiring. They are also extremely cheap for applications like this, so not only are they very flexible, it would be difficult to do a discrete design for a lower size or cost.

Darryl

Modern video encoders use purely digital techniques to generate the composite signal. Writing the algorithms for my converters to do both quadrature modulation for NTSC/PAL and FM modulation for SECAM was relatively trivial. You can also add FIR/IIR filters for limiting the subcarrier bandwidth to the correct spec.

Implementing a discreet analog approach is certainly possible, but unless the source for the component video is coming from a very old piece of equipment, it's being sourced as digital data anyway, so it's just easier and cleaner to do all the work in the digital domain.

The great thing with fpga's is they can be thought of as equivalent to a software based solution but for hardware. You are still physically wiring low level hardware blocks together, but using firmware to do so, so you can change and add to the design ad infinitum without having to actually change physical parts or wiring. They are also extremely cheap for applications like this, so not only are they very flexible, it would be difficult to do a discrete design for a lower size or cost.

Darryl

Hi Darryl,

Thanks for the reply. I won't deny that the FPGA is ideal for spatial/ temporal - rescaling/ interpolation. And certainly generating a composite signal may be straight forward. But what is your signal source?

The source of the signal I was considering would ideally come from a modern DVD player. The quality loss through analog to digital and digital to analog conversion is minimal if the video remains as component Y' Cb', Cr'. Analog component, serial digital (SMPTE259C) or HDMI, is okay. If the signal source is composite NTSC, the results will be compromised. Cascading composite codecs is lossy.

Why I suggested that the FPGA may be over the top is that to actually generate a CPA signal from analog component video should only take a dozen or so discrete transistors. If rescaling and interpolation was necessary, I would not hesitate to say FPGA. But with 525 line 59.94Hz video in and out, I do not think an FPGA is necessary.

My curiosity is now raised and I will ponder a hardware based solution.

Terry

Thanks for the reply. I won't deny that the FPGA is ideal for spatial/ temporal - rescaling/ interpolation. And certainly generating a composite signal may be straight forward. But what is your signal source?

The source of the signal I was considering would ideally come from a modern DVD player. The quality loss through analog to digital and digital to analog conversion is minimal if the video remains as component Y' Cb', Cr'. Analog component, serial digital (SMPTE259C) or HDMI, is okay. If the signal source is composite NTSC, the results will be compromised. Cascading composite codecs is lossy.

Hi Terry,
Certainly obtaining the video directly from a digital source is preferable but not practical for this level of converters. In my professional design work, everything is SDI, quickly becoming 3G SDI but that is unheard of outside the broadcast industry. Consumer level HDMI is hampered by HDCP making it useless unless you want to try to obtain a license which would be cost prohibitive for these low volume converters.

For my low cost converters I use a video front end with a 4 line adaptive comb filter, so while not quite as good as component, it has proven to be more than adequate for the capabilities of these early sets. These parts have the capability to support S-Vid, so this input can be added to these converters. My broadcast WC converter has CVBS, S, and component YUV/RGB inputs but is overkill for this purpose. It uses 10 bit ADC/DAC's with 14 bit minimum internal processing which considerably raises the cost.


Why I suggested that the FPGA may be over the top is that to actually generate a CPA signal from analog component video should only take a dozen or so discrete transistors. If rescaling and interpolation was necessary, I would not hesitate to say FPGA. But with 525 line 59.94Hz video in and out, I do not think an FPGA is necessary.

My curiosity is now raised and I will ponder a hardware based solution.

I don't think it would be quite this easy in analog using baseband component. You need to generate the 3.8MHz carrier, preferably correctly locked to the Hsync (assuming the Hsync from the source is even stable enough although you could free run like consumer vcr's), bandwidth limit and quadrature modulate the R-Y and B-Y and then add back into Y. Potentially an off the shelf part might be able to do at least a portion of this, but it's still a fairly involved design.

The nice thing with an fpga design is you are not limited to the physical hardware. If you want to add a filter, change the carrier frequency or phase, etc. it's just a respin of the vhdl. I have added stuff to clients designs that were not even in the original spec all without touching the hardware.

Darryl

Hi Terry,
Certainly obtaining the video directly from a digital source is preferable but not practical for this level of converters. In my professional design work, everything is SDI, quickly becoming 3G SDI but that is unheard of outside the broadcast industry. Consumer level HDMI is hampered by HDCP making it useless unless you want to try to obtain a license which would be cost prohibitive for these low volume converters.

For my low cost converters I use a video front end with a 4 line adaptive comb filter, so while not quite as good as component, it has proven to be more than adequate for the capabilities of these early sets. These parts have the capability to support S-Vid, so this input can be added to these converters. My broadcast WC converter has CVBS, S, and component YUV/RGB inputs but is overkill for this purpose. It uses 10 bit ADC/DAC's with 14 bit minimum internal processing which considerably raises the cost.



I don't think it would be quite this easy in analog using baseband component. You need to generate the 3.8MHz carrier, preferably correctly locked to the Hsync (assuming the Hsync from the source is even stable enough although you could free run like consumer vcr's), bandwidth limit and quadrature modulate the R-Y and B-Y and then add back into Y. Potentially an off the shelf part might be able to do at least a portion of this, but it's still a fairly involved design.

The nice thing with an fpga design is you are not limited to the physical hardware. If you want to add a filter, change the carrier frequency or phase, etc. it's just a respin of the vhdl. I have added stuff to clients designs that were not even in the original spec all without touching the hardware.

Darryl

Hi Darryl,

I certainly see your points. But the issue at the time was for CPA to optimize luma and chroma resolution. For one to first hand understand whether the abandonment CPA was justified requires a signal with at least the chroma resolution the early NTSC was trying to achieve. CPA was initially intended to convery full bandwidth chroma for both color differ signals of 1.5 MHz. NTSC constricted the Q channel to 500kHz. Secondly the use of a four line adaptive decoder compromises the diagonal luma resolution as well as reducing the vertical chroma resolution. In other words concatenating the two codecs will not give a proper representation of CPA. However, this will only be worth the bother if the display CRT focus and bandwidth to the CRT are up to the job of showing the extra resolution that was intended by the use of CPA.

I also believe the thought of the NTSC at the time was if putting the subcarrier at 3.89MHz, would the subcarrier into luma interference pattern less obvious and allow the luma bandwidth to be somewhat greater? The IQ NTSC standard with the subcarrier at 3.58MHz meant that the luma trap limited luma bandwidth to only about 3.0MHz and with the subcarrier at 3.89MHz, the luma response was effectively extended another 400kHz.

Component video from a DVD player will have reasonable stable sync. I agree that locking the subcarrier to the sync will be a challenge. VHS tape as a source will be totally out of the question since VHS does not fulfil the mathematical subcarrier to Hsync relationship and VHS simply does not have the bandwidth. DVD playback does and is stable.

I would think the reason I would persue CPA encoder without the IQ concatenation would be to see how well CPA would work. I think we would all agree that component 525 video looks very decent. (In fact playback of a good quality component DVD authored from 35mm film looks better than much (if not most) broadcast video purported to be HD).

I agree that a dozen transistors will not account for even the sync divider. But I think a few ASICs may be adapted to work in a CPA encoder. I trust the restoration of this set (if it is indeed a CPA Prototype) will come to fruition and the opportunity presents itself to compare CPA encoding schemes. Besides I would like to see how well an FPGA solution will work.

All the best,

Terry

For one to first hand understand whether the abandonment CPA was justified requires a signal with at least the chroma resolution the early NTSC was trying to achieve.

To this end, I don't honestly need to see it to understand what the engineers saw back in 1953. I have a few papers that detail some of the issues they themselves saw when using CPA, and their reasons for abandoning it's use. The flicker was seen as objectionable, though their notes indicated that it was not too bad at low brightness levels. Additionally, as was found by the later tests, I/Q sets produced pictures that were acceptable for the general public and I doubt anyone pitched a fit or even noticed a difference when sets went to narrowband shortly thereafter. Let's remember that the average person back then (and I'd argue even now) wasn't so concerned about picking apart every little detail as some of us are. I'd assume that they were enthralled by simply having a color picture on the screen, much less being able to afford one as expensive as they were.

I can tell the difference in picture quality between a wide bandwidth set like my 21CT55 and a narrow bandwidth CTC-4, but most people would be hard pressed to see the difference. All that said, it would be important to feed a CPA set with signals having the correct bandwidth in order to evaluate its performance. But since this set doesn't appear to have a CPA switch in it, I don't think we will ever know.

Hi Terry,

I certainly see your points. But the issue at the time was for CPA to optimize luma and chroma resolution. For one to first hand understand whether the abandonment CPA was justified requires a signal with at least the chroma resolution the early NTSC was trying to achieve. CPA was initially intended to convery full bandwidth chroma for both color differ signals of 1.5 MHz. NTSC constricted the Q channel to 500kHz. Secondly the use of a four line adaptive decoder compromises the diagonal luma resolution as well as reducing the vertical chroma resolution. In other words concatenating the two codecs will not give a proper representation of CPA. However, this will only be worth the bother if the display CRT focus and bandwidth to the CRT are up to the job of showing the extra resolution that was intended by the use of CPA.

I also believe the thought of the NTSC at the time was if putting the subcarrier at 3.89MHz, would the subcarrier into luma interference pattern less obvious and allow the luma bandwidth to be somewhat greater? The IQ NTSC standard with the subcarrier at 3.58MHz meant that the luma trap limited luma bandwidth to only about 3.0MHz and with the subcarrier at 3.89MHz, the luma response was effectively extended another 400kHz

All valid points. To see CPA as it was originally envisioned would take higher chroma bandwidth than available with I/Q NTSC. This has also been brought up with the converters when displaying to a CBS sequential set which is one of the reasons I added the component inputs to the WC converter. As Nick pointed out however, it takes a trained eye to see any difference on the few CBS sets when using a composite versus component input.

Keep in mind that we are not using a strict NTSC signal as a video source. When coming from a set top box, DVD, DVR, basically any digitally sourced device, the video encoder is probably not doing Q limiting per the spec. This along with the fact that the source is clean and we are connecting directly to the set, many other limiting factors have been eliminated or greatly reduced.

Component video from a DVD player will have reasonable stable sync. I agree that locking the subcarrier to the sync will be a challenge. VHS tape as a source will be totally out of the question since VHS does not fulfil the mathematical subcarrier to Hsync relationship and VHS simply does not have the bandwidth. DVD playback does and is stable.

This is why I prefer digital solutions. The WC converter has a built in 8 frame memory that acts a TBC, so regardless of the source, the output will always be stable and correct. While that is not as important in this application, it makes a world of difference for the CBS sets. Once you get those wheels up to speed and in sync, you don't want the sync phase changing :)

I would think the reason I would persue CPA encoder without the IQ concatenation would be to see how well CPA would work. I think we would all agree that component 525 video looks very decent. (In fact playback of a good quality component DVD authored from 35mm film looks better than much (if not most) broadcast video purported to be HD).

Whenever a new format comes up, I always add it to all my converters, so since it will also be in the WC converter, we would be able to compare the effect of the different inputs.

For an input source on any of these comparisons we really should be using 10bit uncompressed video, or at least a minimally compressed one like DigiBeta. While DVD's can look good, as a design engineer the 8 bit quantization and mpeg2 compression are horrendous as evidenced in fast motion and quantization noise in dark scenes.

Great discussion Terry. I guess we need to see what Nick discovers as he documents the set.

Nick, it's disappointing to hear the set does not have the CPA switch and may be too far modified from it's origins to put it back.

Darryl

Nick, it's disappointing to hear the set does not have the CPA switch and may be too far modified from it's origins to put it back.


Regardless, it's a very interesting chassis to look at even if it never works. It's a great historical piece, since it's obvious they were trying different things with it. It has chassis stampings labeled 'CPA' and 'DELAY', and there are a pair of 12AU7's not connected to anything that look as if they may have had something to do with CPA at some point but now serve no purpose. Looking at the local oscillator, it has a pair of phase shifting networks on it's output which then go directly to the R-Y and B-Y demodulators. It resembles an NTSC circuit more than anything else, so that's what I'm putting my money on. Still not clear if it's I/Q, but since it was what they eventually decided on it's highly probable. Nailing down the years it was worked on would help, but there are no identifying marks on it.

Yes, it is disappointing that the CPA switch cannot be found. Despite the sketchy information that is to be currently found on early NTSC development, the CPA decoder could possibly be reconstructed.

I also appreciate the insight to the FPGA design converter. Thanks, Darryl.

This set nevertheless is a very unique part of television history and I am glad it has a good home.

Terry

Was watching TV the other day, and noticed A&E is advertizing the new 'Shipping Wars' show. This is the series that Roy told me was filming him at the time the set was delivered, so start setting your DVR's in case I appear on screen! :thmbsp:

http://www.shippingwars.net/

http://www.youtube.com/watch?v=yV6CTqduv-I

Hey Nick, you're a TV star!

You were just moments ago on the new Shipping Wars show. Hopefully you were recording it. They showed picking the set up from Harry just before the break and then delivering it to you. Very nice.

Darryl

Yep, just saw it myself!

It was a short spot, but they managed to make the CTC-4 look better than it actually did. They asked if any of the sets I had worked, so I fired up the Director and they took some footage that actually made it to the episode. It wasn't working as well as it normally does that day (predictably), but it didn't do too badly. I only wish it hadn't been such a small spot, my hope was to get a few words in edgewise. Oh well, I'll have the last word at the convention!

Aw, fudge! I missed it. Well, it will be shown again. Way to go, Nick!

Shipping Wars also airs overnite Wed. in the early AM. Airs again this Saturday at various times in the afternoon. This on A&E HD and standard networks. Check your cable listings.

-Steve D.

Shipping Wars also airs overnite Wed. in the early AM. Airs again this Saturday at various times in the afternoon. This on A&E HD and standard networks. Check your cable listings.

-Steve D.

Just checked here on the east coast, supposed to be at 11PM both SD and HD. I set the DVR to record...

Judging by the trailer I wouldn't let them touch anything of mine!
They might smash something just to spice things up.

Real life is nothing like these "Reality" shows.

Aw, fudge! I missed it. Well, it will be shown again. Way to go, Nick!

Thanks John, I'm currently working on a way to download the video from my DVR so everyone has a chance to view it. BTW, I was recently in Pembroke Pines and realized that on my way back to North Carolina I drove right past your place. I should have given you a call, but the thought didn't cross my mind until now. I did stop by the UDT/SEAL museum in Fort Pierce though, that was pretty cool.

http://miniman82.4t.com/images/seal/Photo01071247a.JPG

Judging by the trailer I wouldn't let them touch anything of mine! They might smash something just to spice things up. Real life is nothing like these "Reality" shows.

I do think that a lot of these shows have made up drama written into them, but Shipping Wars is more or less accurate. Roy was telling me all about his trials and tribulations getting started in the freelance world when he got here, and the show sums it up pretty well based on what he told me. No help but what you bring, sheisty and sometimes underhanded people who don't understand your work, routes that don't always work out, impossible time frames, and top it all off with unintended vehicle breakdowns and law enforcement officials who could care less that you're just trying to make an honest living.

All that said, I was in constant contact with Roy and he was very good about letting me know what was going on every step of the way. I used to just roll my eyes when people on TV call themselves 'professionals', but Roy really means it. He's a character no doubt about that, but I'd hire him again no questions asked. He did everything he said he would do and let's face it, it's getting harder and harder to find people like that these days.

As for things getting damaged in shipment, it's all in how you pack it. If you pack well enough, even a CRT can make it through some bad conditions. I had a 21AXP22 U-Shipped to me from Michigan in nothing more than a ratty old torn up box, it made it just fine. Can't say that for UPS, who managed to destroy a rebuilt CRT from Scotty even though it was in a purpose made CRT container. :thumbsdn:

As things stand right now, I'm far more comfortable using UShip for delivery of fragile items than any other service. You guys should give it a shot next time you need a valuable set moved, the prices might surprise you. Hate for this to sound like a pitch, but I have been impressed so far with the way things have gone.

more comfortable using UShip for delivery of fragile itemsU-Ship is what I used to ship the TM-10 monitor long distance. This after wasting a couple of months scratching around and searching for alternatives. It was delivered safely, a couple of days sooner than promised, for about 1/3 the price I was quoted by Craters & Freighters. (The seller bolted it to a pallet, covered in a sturdy cardboard container, and delivered it to the terminal, and I gladly paid him for that.)

Phil Nelson

Aw, fudge! I missed it. Well, it will be shown again. Way to go, Nick!
John-

If you have a computer hooked up to a decent display, and a pretty fast Internet connection, you can watch shows directly on www.aetv.com . I use a Windows 7 computer with Windows Media Center as my regular TV (on a 46" or 92" display), and in full-screen mode the shows on the site look pretty decent even in high-def. I watched a few episodes of the "Hoarders" show this way (and then realized I need to get rid of some things!).

Hey Nick, you're a TV star!

You were just moments ago on the new Shipping Wars show. Hopefully you were recording it. They showed picking the set up from Harry just before the break and then delivering it to you. Very nice.

Darryl

Ok, per Zap2it, there are two Shipping Wars episodes currently running:

Pilot: (Steel horse and Feed me Seymour}

Double Down and Bean Town: (Two large boats & British phone booth)

Which episode?

Bean town is the one, the TV is a little more than halfway through the episode.

Hi All! Happy New Year

Hposter here....

well, I just viewed the Shipping Wars scene of the pickup of the prototype CRT for miniman82, and it was a real set-up! The producer told Anna and I, tell us all about your TVs..and the prototype in particular. I see that when they edited it, the trucker adds, I hate it when they tell me about their stuff....which is actually pretty funny, since his producer asked us to tell them. I see from his expressions, that it was a set-up, because he has a grimace...which meant the producer already knew exactly how he would edit the shot.

Then they had me go into the truck 3 or 4 times (only once is shown), to ask him about how the CRT/set was being packed...'Make it seem like you're very interested that it's secured properly' That's where they add, in editing, that he hates to have people question his technique. Hmmmm

Of course, it was delivered with no catastrophes, so that was nice!

For anyone that wants to record the video, or parts of it, go online and download a free program called HyperCam 2. Then, set up the screen, use HyperCam 2 to delineate the area of your screen the playback is actually on, and click record..then start the video..and Viola! you have an AVI clip that Media Player or others can play...so you can see that pesky Poster, over and over again.

If you have problems with no sound, just plug in your mike, put it touching your speakers, and then it'll pick up the audio as well.

See ya on TV...(I hope not!) Harry

I got the feeling you were 'asked' to bother him as well, but what's reality TV without drama right? Roy was actually a nice guy, we BS'd a while during down time when the camera crew was handling business. He was saying they actually make a ton of money, it's not nearly as bad as they make it seem.

Thanks for the insight into making videos, but am I understanding you correctly in that you'd be making a video by filming a TV to get the footage? What I'm looking for is a way to directly download from the DVR, so it's as high a quality as possible. I don't know if filming my DLP TV would work, but I suppose I can give it a shot. I have a Sony handycam that uses digital tape, so it might not be too bad. For that, I already have an editing program.

Yes, drama it is!


On the video recording, when you play the video on the computer screen (I still use over-the-air broadcast--no cable, no DVR's--so computer downloads are the only way for me!!) this program allows you to record it as it downloads. There is a setting for 1028 on many downloads, so you could record that good.

Actually, I didn't realize anyone watched TV on televisions anymore..I see all the kids use i-phones or e-phones or...something. (No, I don't have a smart phone, either!)

Hey Nick,

If I'm not mistaken.
Looks like we've really come full circle. If you plan to record (film is not a proper term here), the "Shipping Wars" episode off the screen, it can be likened to the old kinescope recording of live programs back in the 40's & 50's.

-Steve D.

I have an old Sony Handycam and tried to use it years ago to record some brief video clips of my restored TVs. The result had dark, slowly moving horizontal bars, which I attributed to different frame rates or suchlike.

Phil Nelson

I've posted the pertinent part of the show at:

www.tech-retro.com/images/HPandNW.mp4

Darryl

Thank you for posting that, Darryl.

For others discussing recording from your computer, the program Harry described is going to save the video from within the computer itself, as you play the show in a window on the computer monitor. There is no pointing of a camera at the screen at all (even though the program name has the word "cam" in it).

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/prototype%20color%20set/video/HPandNW.mp4.AVI

I saw the show and knew it was you and HP. I haven't looked at this thread for a few months, so I came back just now to confirm that I was correct.

My son and I were watching it and I said the set and the back story seemed familiar. His response was, of course, "Dad, anything old with tubes in it looks familiar to you!".

Congrads on getting on TV!




Was watching TV the other day, and noticed A&E is advertizing the new 'Shipping Wars' show. This is the series that Roy told me was filming him at the time the set was delivered, so start setting your DVR's in case I appear on screen! :thmbsp:

http://www.shippingwars.net/

http://www.youtube.com/watch?v=yV6CTqduv-I

I have an old Sony Handycam and tried to use it years ago to record some brief video clips of my restored TVs. The result had dark, slowly moving horizontal bars, which I attributed to different frame rates or suchlike.

Phil Nelson

I got a Panasonic prosumer camera, and can record CRT's just fine with it. I use a 1/60th shutter at 60 frames per second progressive, and adjust the iris for a good picture, and the result is an awesome screen grab.

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...

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

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.

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.

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!

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.

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/images/RCA-21T176-Sams-157-8.pdf

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

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

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.

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

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. :-)

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

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.

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.:thmbsp:

Nick, I'm sure we can get it running as a CPA set, assuming the flyback is good. There are replacements available for all the other parts, and I'm sure we can figure out the cut wires. Even if we can't find a delay line to fit in an IF can we can put a standard one under the chassis. And I'm sure Darryl can make us a converter to generate a CPA signal.

We'll have to figure out which route to go after you have time to sit down with the chassis, just let me know when to ship it and I'll work on getting it boxed up. Do you need the power supply along with the main chassis?

Don't think we'll need the power supply. If we need to power it up I'm sure I have something at the museum that would work.

I could bring my bench supply if needed.

You might see if there is some way to restore the set such that it could easily be switched between CPA and whatever state you determine that the engineers left it in. I think that having it in the last state that it worked in is as historically valuable as having it work as a CPA set.

It would be interesting to see what a CPA set is capable of, and Darryl has said he can program a magic box to output that standard. I think we should at least try it, for S&G's. After that, it will probably end up as an NTSC set.

Here is what I'd to. To get it working as a NTSC set:

1. Finish documenting the chassis as it is.
2. Figure out what it needs for power supply voltages.
3. Figure out how to connect the cut wires.
4. Determine what parts are missing (delay line, etc.) and find replacements.
5. Fire it up as a NTSC set and see if it works. Make whatever alignment changes are necessary to get a NTSC picture.

Then, configure it for CPA

1. Design the missing CPA circuits and install the components.
2. Fire it up as a CPA set and make whatever alignment changes are necessary for CPA.

Hi All,

I have been away and I have been reviewing the documentration we have collected in recent months regarding CPA.

Upon comparing Nick's prototype and the RCA patent for the CPA switching, there are striking similarilties in the components. The CPA transformer and components around it in the prototype follows the patent even down to some components.

I am trying to derive a reliable field switcher using only four triodes (the two 12AU7's). This is proving a challenge because one pair of triodes would provide the bi-stable device for alternate fields, one triode for field recognition, one triode for alternate field bi-stable switching and an extra triode as the field pulse buffer (as shown in the figure 13 Hazeltine drawing). The field pulse buffer is the fifth triode so the question to ask is: is there a spare unused trode on the chassis besides the two 12AU7's? Or is there possible a spare low impedance winding on the vertical output transformer which could produce the pulse?

Also the transformer on the plate circuit of the 6U8 3.89MHz oscillator buffer appears redundant. The CPA transformer is all that would be required and I wonder if it originally attached to the buffer plate directly? I find the separate subchassis for the oscillator curious and wonder if it was later fitted to fulfil subsequent modifications?

In the timeline of development of CPA with symmetrical vestigial sideband chrominance channels thru to the development of the IQ asymmetrical sideband solution, I suspect there were intermediate but "unofficial" modifications to the system. If I were in their shoes in 1952 when CPA with the 3.89MHz subcarrier operation was proving difficult to tame and growing unpopular, I would have been inclined to experiment with CPA back at 3.58MHz. The benefit of 3.58MHz CPA would be to make each chrominance channel sidebands more symmetrical to help reduce the CPA flicker.

Introducing the IQ solution would mean different bandwidth I Q chrominance channels which would mean a second delay line for the I channel. At this stage they may or may not have thought about the design of a "simplified" narrowband chrominance channel decoder. Without seeing any evidence means that discussion of this is pure conjecture. Making the set a switchable 3.58MHz CPA/non-CPA receiver would not be much of a problem but full IQ demodulation I feel would be out of the question.

I plan to complete my diagram in Visio which I will hopefully tonight. Any thoughts, comments or criticisms are most welcome.

Terry

Making the set a switchable 3.58MHz CPA/non-CPA receiver would not be much of a problem but full IQ demodulation I feel would be out of the question.

Terry

Seems reasonable and historically cogent. Particularly since there is no longer 1953NTSC IQ to drive the set anyway.

Pete

Terry,

There is a 12AX7 and 12AT7 near the vertical section. One of them is for the convergence, but we don't know what the other one does. I suspect you have a total of 5 triodes to work with. When I get the chassis the first thing I'll do is trace those circuits.

Here is an article from 1952 about RCA color. Nick, could this be the cabinet your chassis was in?

www.earlytelevision.org/color_tv_today.html

I don't think so, but it's hard to tell.

Steve,


Proto set is on it's way to your door, I shipped it this morning. USPS w/insurance and tracking. I secured it inside the box as well as possible, hopefully they don't manhandle it. I put stickers all over it, so it's pretty obvious the contents are fragile.

Nick

I made a CRT adapter mask to mate the proto CRT to a CT-100 cabinet, for the purpose of ETF demonstration. It's a board with trimmed 16" B&W mask secured to it, the board has mounting slots cut into it that are correct for the CT-100 cabinet so no modifications are needed. No hole drilling on the cabinet, just R&R the 15G with the proto stuff. I have also decided that having the bare CRT face in the cabinet could be a liability, so for safety's sake I will have a piece of plexiglass cut to the size of the opening in the cabinet to protect wayward fingers from getting zapped. This is what it looks like.

http://videokarma.org/attachment.php?attachmentid=173764&d=1332729115

Nick,

That mask looks good, cant wait to see the tube in operation and see such a historical tube in operation!

Matt

Nick, do you have extension cables to connect it to a CT-100 chassis?

No, Bob does. The only thing that will be required is the longer anode wire, everything else should reach. Did you get hte chassis yet?

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

Steve, your assessment of the "later mods" certainly makes sense. I am just glad that this wonderful piece of history did not get put on the dump as so very many wonderful sets did in years past...

Steve, I agree that your assessment makes sense, although you would be surprised at some of the breadboarding techniques I have seen over the years. We had one fellow (X) who built prototypes by soldering a 3-dimensional haystack of parts onto a tin sheet. (His soldering was good, not cold joints.) Once it worked, he would unsolder all the ground connections from the tin sheet and put the haystack in the cupboard above his bench. These were known in the lab as "(X) piles."

Good thing he didn't do paperwork, you could have called them "X-Files". LOL! :D

Better a well-diddled prototype than dozens of revisions once in production! Ask the techs who test, cal, diagnose and repair them!

I got the prototype chassis from Nick today and started documenting the remaining circuits. I'm starting with the power supply lines, then I'll do the sweep sections.

I have a new theory about the history of this set. The modifications are very unprofessional, with cold solder joints and midair connections. I can't believe that RCA engineers would do that kind of work. I think the set was abandoned by RCA after its life as a CPA prototype, and the later mods were done by someone who got the chassis, probably an attempt to make it work with NTSC.

Steve,
So then you will be restoring this as a CPA set? If so is there any chance that at least the sweep and decoder sections could be working by the convention? I can get started on developing a CPA converter.

BTW does anyone have the actual spec for CPA? Can we assume that most things just match NTSC (burst length, phase and position) and only the R-Y inverted every other frame?

Darryl

I don't know how much I can get working by the convention. There are lots of cut wires and dangling components. If I can figure out where everything goes I may get most of the set working.

BTW does anyone have the actual spec for CPA? Can we assume that most things just match NTSC (burst length, phase and position) and only the R-Y inverted every other frame?
DarrylDarryl

Fink, Television Engineering, 1952 edition shows the "color-phase synchronizing pulse" in figure 417 on page 549, which may help.

Pete

I don't know how much I can get working by the convention. There are lots of cut wires and dangling components. If I can figure out where everything goes I may get most of the set working.


Biggest thing will be figuring out what's up with the pulse regulator. I was only ever able to get about 5kv out of the flyback, but it didn't burn up either. That says to me it's probably still good, but the regulator was dragging it down. Once you trace that part of the circuit, we'll know more.

Darryl

Fink, Television Engineering, 1952 edition shows the "color-phase synchronizing pulse" in figure 417 on page 549, which may help.

Pete

Hi Pete,
I have Fink's other books but not that one. Could you scan the relevant pages?

Thanks,
Darryl

Hi Pete,
I have Fink's other books but not that one. Could you scan the relevant pages?

Thanks,
Darryl

Here's a photo of the page.

Pete

Looks to me like there is one newer yellow electrolytic soldered under the chassis.
I'm a big fan of getting rid of all the leaky paper caps. But I have also had very good
luck with electrolyics in cans from the pre-wars up thru the mid 50's. I just reform them with a very low charge current and they are not leaky. It is not like they are in a place to cause a lot of damage when they short. My TRK-120 has all of it's original electrolytics and it works fine.. I thought Harry told me he got it from a picker from the Lancaster area.. I'll have to go back and check my emails.

I am glad to see someone else saving the early dry electrolytics. I reform them as well and have little problem with them.

I have also had good luck with early-mid 1930's wet electrolytics. If the electrolyte has not leaked (due to perished rubber seals) I have been able to reform and use these as well. My old Scott radio has a wet electroytic from1935 and it maintains the 20ufd with vitually no leakage. The reforming took about four days incrementally increasing the voltage across the wet electrolytic until the full rated voltage was reached. As the capacitor reforms, the leakage current drops and the wet electolytic leakage remains constant at about 50uA at full voltage.

The post WWII dry electrolytics reform pretty fast but I still give each a couple of days to ensure the leakage is below 100uA and remains there.

Terry

Thanks Pete. That is certainly different than what I expected. The burst is down in the sync rather than riding at the black level. I still need to find out how they phased the burst and components.

Darryl

Thanks Pete. That is certainly different than what I expected. The burst is down in the sync rather than riding at the black level. I still need to find out how they phased the burst and components.

Darryl

Darryl,

I have an article from p338-343 in the March 1953 Proceedings of the I.R.E. where they describe how they generate a CPA NTSC color bar test pattern if that would help. They describe how these signals were used in the late 1951 and 52 tests. The color sync was 3.89 Mc

I could email it to you if you think it would help. The files are a little too big to post here.

James.

Darryl,

I have an article from p338-343 in the March 1953 Proceedings of the I.R.E. where they describe how they generate a CPA NTSC color bar test pattern if that would help. They describe how these signals were used in the late 1951 and 52 tests. The color sync was 3.89 Mc

I could email it to you if you think it would help. The files are a little too big to post here.

James.

Definitely! That sounds like it might contain enough information to fully implement CPA.

Thanks James

PM sent

Thanks Pete. That is certainly different than what I expected. The burst is down in the sync rather than riding at the black level.
DarrylHere's something from Loughlin published by IEEE in 1984; it seems to explain the odd burst.

Pete

Stands to reason the burst should not be on a pedestal then, if issues were encountered. The receiver could be modified to work that way, in the event it was built for the burst being on a pedestal. Circuit mods would likely be minimal.

Nice catch Pete.

From the article it sounds like it was a certain monochrome set that had trouble with the burst being in the sync area, not the CPA set. I'm also getting out of this article that they changed the burst to ride on the black pedestal for NTSC not for the initial CPA. I guess it's easy enough to just make this switchable in the converter :)

Darryl

Here is a preliminary schematic of the HV regulator circuit:

http://www.earlytelevision.org/images/proto_color_sweep.pdf

Nice catch Pete.

From the article it sounds like it was a certain monochrome set that had trouble with the burst being in the sync area, not the CPA set. I'm also getting out of this article that they changed the burst to ride on the black pedestal for NTSC not for the initial CPA. I guess it's easy enough to just make this switchable in the converter :)

Darryl

Darryl,

The only reason I can think of for putting the burst in the sync region is to prevent it being visible during retrace on some existing receivers without power blanking. But that also means that most existing receivers will see it as a second H sync pulse. I think it's an excellent idea to make this switchable so we can see the effects of one case or the other on the sets at ETF.

According to Bernard Loughlin, it was early determined that the burst on the pedestal caused sync instability problems and the pedestal was removed.

Perhaps making it switchable is commendable but I think by the time Nick's prototype was tested the burst pedestal was already just history.

Terry

Here is a preliminary schematic of the HV regulator circuit:

http://www.earlytelevision.org/images/proto_color_sweep.pdf

Interesting. Perhaps at this time, practical shunt HV regulation was not yet viable?

the circuit appears to provide a degenerative-pulse bucking arrangement so that when the HV rises, the 6BQ6 reduces the pulse to reel back the HV.

Terry

Nice catch Pete.

From the article it sounds like it was a certain monochrome set that had trouble with the burst being in the sync area, not the CPA set. I'm also getting out of this article that they changed the burst to ride on the black pedestal for NTSC not for the initial CPA. I guess it's easy enough to just make this switchable in the converter :)

Darryl

Note that CPA was NTSC!

Note that CPA was NTSC!

I guess I only consider CBS and today's analog color standard as NTSC since those were the ones ratified. CPA, dot sequential and the rest were only lab exercises or presentations to the NTSC.

I am envisioning an issue with CPA and compatibility with the SCRF converters. Since these converters don't have frame memories they can't do frame rate conversion. This means the line and frame timing will match modern standards so there will not be a exact relationship between the line timing and sub-carrier frequency. We would need to either shift the sub-carrier frequency slightly, or accept a non-integer relationship. Not sure if the later would be a problem as I have not seen how the set determines which field phase it's in. The more expensive WC converter can do whatever we need but is overkill.

Darryl

I've documented a bunch more of the schematic. Note that I made some changes to the HV regulator I posted earlier. Another interesting find is a pot in the cathode of the hor. output tube, labeled "Phase".

Also, one half of one of the tubes we thought were for the CPA switching is actually in use as a sync cathode follower. Tomorrow I'll finish the vertical sweep section.

I guess I only consider CBS and today's analog color standard as NTSC since those were the ones ratified. CPA, dot sequential and the rest were only lab exercises or presentations to the NTSC.

I am envisioning an issue with CPA and compatibility with the SCRF converters. Since these converters don't have frame memories they can't do frame rate conversion. This means the line and frame timing will match modern standards so there will not be a exact relationship between the line timing and sub-carrier frequency. We would need to either shift the sub-carrier frequency slightly, or accept a non-integer relationship. Not sure if the later would be a problem as I have not seen how the set determines which field phase it's in. The more expensive WC converter can do whatever we need but is overkill.

Darryl

Darryl,

The DOT sequential system is RCA. But the CPA test came under the auspices of the NTSC. I believe Bernard Loughlin refers to CPA in the context of NTSC.

Can you explain your concern over compatibility with the SCRF?

It would seem to me that the current NTSC frame rates are acceptible for CPA since the NTSC frame rates ensure proper chroma interleaving with the presence of the 4.5MHz sound carrier.

Hence if the current scan rates are used, the standard NTSC subcarrier relationship (odd integer multiple of half the horizontal rate would suffice for the nominal 3.89MHz. But CPA means that with only a half line offset, the Y and R-Y spectra will align to form a vertical dot line up and resulting dot pattern. Hence I believe a quarter line offset is required.

The nominal 3.89MHz results in:

3890000/fH/2 = 494.4622...

The closest quarter line offset multiple is therefore 493.75

Therefore the CPA fsc = 493.75 x fH/2 = 3.884396MHz

I believe this CPA subcarrier can be used with current NTSC scan rates and provide the best interleaving of the chroma.

What do you think?

Terry

Terry,

The CPA chroma frequency was defined as exactly 495/2 * Fh. Using the original Fh of 15,750.00Hz yields exactly 3,898,125Hz. This also means that there was an exact relationship between the phase of the chroma carrier and the line frequency (i.e. the phase and position of the chroma carrier will be exactly the same on every other line). From what I have read there was no half line offset. That's something that came later. Of course anything can be done now, but I would recommend putting the set back to as close to original as possible, warts and all, to verify what they saw during the original tests. This will result in a stationary, visible pattern but that's what they would have seen.

So using the current NTSC line frequency of ~15,734.27Hz and the same 495/2 yields ~3,894,230.77Hz. This means that to maintain the same locked phase relationship between the chroma carrier and the line, we would have to use this new frequency. If we wanted to use the original 3,898,125Hz, we would loose the locked phase relationship between the chroma carrier and the line. This will change the visible dot pattern.

The issue with the SCRF converter is there is no frame memory, so rate conversion cannot be performed. The line output timing would match the line input timing, or 15,734.27Hz. With the WC converter the output is complete independent of the input and anything can be done.

So is there a design reason to have the chroma locked to the line, or does it even matter with this set? Do we want to observe the set exactly as it would have appeared during the tests? Since a crystal will need to be cut it could easily be cut for either frequency, or both could be cut and tried. To the converter it's just firmware so it doesn't matter. This will ultimately be Nik's/Steve's call assuming they take the set all the way to operation on CPA.

Darryl

A 3.58Mhz crystal is simple, just take one from a CTC-2(B) chassis and plug it in- it's the same exact socket. For a 3.89Mhz one though, there would have to be some sort of miracle for an original to turn up. The simple solution there is just to have one made, I understand it's actually pretty cheap because RC car folks have it done all the time.

Terry,

The CPA chroma frequency was defined as exactly 495/2 * Fh. Using the original Fh of 15,750.00Hz yields exactly 3,898,125Hz. This also means that there was an exact relationship between the phase of the chroma carrier and the line frequency (i.e. the phase and position of the chroma carrier will be exactly the same on every other line). From what I have read there was no half line offset. That's something that came later. Of course anything can be done now, but I would recommend putting the set back to as close to original as possible, warts and all, to verify what they saw during the original tests. This will result in a stationary, visible pattern but that's what they would have seen.

So using the current NTSC line frequency of ~15,734.27Hz and the same 495/2 yields ~3,894,230.77Hz. This means that to maintain the same locked phase relationship between the chroma carrier and the line, we would have to use this new frequency. If we wanted to use the original 3,898,125Hz, we would loose the locked phase relationship between the chroma carrier and the line. This will change the visible dot pattern.

The issue with the SCRF converter is there is no frame memory, so rate conversion cannot be performed. The line output timing would match the line input timing, or 15,734.27Hz. With the WC converter the output is complete independent of the input and anything can be done.

So is there a design reason to have the chroma locked to the line, or does it even matter with this set? Do we want to observe the set exactly as it would have appeared during the tests? Since a crystal will need to be cut it could easily be cut for either frequency, or both could be cut and tried. To the converter it's just firmware so it doesn't matter. This will ultimately be Nik's/Steve's call assuming they take the set all the way to operation on CPA.

Darryl

Hi Darryl,

The shift from the horizontal rate of 15,750Hz to 15750 x 1000/1001Hz was only to accommodate the 4.5MHz sound carrier. Hence shifting the subcarrier to accommodate the slightly lower scan rates should be inconsequential. I trust you agree the frame rate conversion is not necessary.

The half line offset I referred to as an odd number multiple of half the line rate and is what is used for the current NTSC system.

PAL uses a quarter line offset so that there is a quarter cycle less of subcarrier per line. This means that when the R-Y axis reverses line by line, there will not be the chance of vertical dot line up.

I have not found any information that CPA used a quarter line offset but I included in my calculation anyway.

My thoughts are this: a fixed relationship between CPA subcarrier and the scan rates is desirable but not essential. The frequency response of VHS tape is restricted so that there is no line locked relationship to fsc in VHS tape and it looks pretty good. If however wider luma bandwidth is desired (through comb filtering the source video) then maintaining a locked frequency relationship.

The quarter line offset (as used with PAL) I believe applies to CPA. But is this correct? (It requires some thought) And would the visual field averaging require the quarter line offset? Perhaps it was not used or was not necessary?

Perhaps the NTSC in 1952 was preoccupied with the edge flashing artifacts and so did not get around to thinking about CPA interleaving in greater detail? If that is the case, I would proceed with CPA fsc = 495 x 15750/2 x 1000/1001.

Hi Terry,
Hi Darryl,

The shift from the horizontal rate of 15,750Hz to 15750 x 1000/1001Hz was only to accommodate the 4.5MHz sound carrier. Hence shifting the subcarrier to accommodate the slightly lower scan rates should be inconsequential. I trust you agree the frame rate conversion is not necessary.
I believe shifting the CPA subcarrier to match the current line rate is the right thing to do. While it won't use the original subcarrier frequency, it will use the original subcarrier to line rate relationship and will provide for the original viewing experience.

The half line offset I referred to as an odd number multiple of half the line rate and is what is used for the current NTSC system.

PAL uses a quarter line offset so that there is a quarter cycle less of subcarrier per line. This means that when the R-Y axis reverses line by line, there will not be the chance of vertical dot line up.

I have not found any information that CPA used a quarter line offset but I included in my calculation anyway.
I had included in my prior response a section on how current NTSC and PAL formats are constructed but later removed it. This gets back to my previous comment about what is to be accomplished. (see below)

My thoughts are this: a fixed relationship between CPA subcarrier and the scan rates is desirable but not essential. The frequency response of VHS tape is restricted so that there is no line locked relationship to fsc in VHS tape and it looks pretty good. If however wider luma bandwidth is desired (through comb filtering the source video) then maintaining a locked frequency relationship.

The quarter line offset (as used with PAL) I believe applies to CPA. But is this correct? (It requires some thought) And would the visual field averaging require the quarter line offset? Perhaps it was not used or was not necessary?

Perhaps the NTSC in 1952 was preoccupied with the edge flashing artifacts and so did not get around to thinking about CPA interleaving in greater detail? If that is the case, I would proceed with CPA fsc = 495 x 15750/2 x 1000/1001.
I think your last comment is pretty close to how I feel. While we can certainly use some of the "tricks" applied to current NTSC and PAL to make the image look better, and while this would be a worthwhile exercise to see what could have been, my feelings are the initial design goal would be to recreate CPA exactly as it would have been during the trials.

From my point of view none of the specifics matter other than what the final target is. Since it's just VHDL coding and requires no physical hardware modifications to the converter, we can play with the specifics ad infinitum. (actually the FLASH memory is only rated for 100K write cycles :) )

Some impact would be imparted on the set as specific crystals would need to be cut for different trials. This is not expensive or difficult, but needs to be considered. Since the crystal is socketed it could be quickly replaced if you want original performance or "enhanced" performance.

If you could work through the specifics of what the best enhanced format would be, I can get it coded and then we would have both available for testing.

Darryl

I've just about finished the documentation of the schematic.

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

There are a few pieces missing, but nothing important. Here are the significant things I found.

1. There are only 3 triode sections available for CPA switching (V24, V25A). I suspect that a sync cathode follower (V25B) was added after CPA was removed, so that would make 4 triodes. The Rauland switching took 5 triodes. How did RCA do it with 4?

2. The chassis has a pot in the cathode circuit of the horizontal output tube labeled "phase". How would that have been used in CPA?

3. Though there is a complete vertical dynamic convergence circuit (V27A), most of the horizontal circuit is missing. There is a triode (V28A) connected to the convergence transformer, but no sign of any controls, other than a remnant of fine wire connected to V28A plate. I can find no place that the controls could have been mounted.

Next I'll fire up the reference oscillator/amp and see if I can find what frequency it is peaked to.

Steve,

I suspect the phase pot had nothing to do with CPA, but rather converngence. The CTC-5 did convergence with wave forms coming off the output tube cathode, perhaps it's the same here.

Nick, I'm sure you're right. I didn't think of that, but it makes sense.

Important update:

Steve has informed me that he found a fault in the deflection yoke- a broken wire. This is what was causing the low HV issue, and now the chassis is making a healthy 17kv! This is a very good sign that the flyback is indeed still good, and bodes well for a go at chassis restoration. Still left to figure out is the regulator tube, and how it functions. If the regulator can be made to work, it's looking like we may have a go at a working CPA receiver before the year is out. Naturally we still need to nail down the subcarrier frequency, as that will determine our course in the rest of this.

Nice to hear. Keep at it, and good luck with the project.

You can follow the restoration here:

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

Here is the series of pictures from the convention, where we mounted the proto CRT into Bob D's CT-100 donor cabinet and attempted to run it with a CT-100 chassis.


Begin with a spare CT-100 cabinet.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5304A.JPG


Remove factory CRT mask.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5305A.JPG

Prefabbed proto CRT 'conversion' mask, plexiglass hasn't been installed yet.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5306A.JPG

Place conversion mask in cabinet.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5307A.JPG

Install plexiglass into front of conversion mask, secure with self tapping wood screws.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5308A.JPG

View from the rear of the cabinet.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5309A.JPG

Install proto CRT into custom mask. This required the use of a CT-100 support ring, held in place by support rods that were fabbed on site because the factory ones were far too short. These were Bob Galanter's idea, made from threaded rod that we cut to size. We then heated the ends with Bob's mapp gas torch to bend J-hooks into the end so they would fit into the U-hooks in the CT-100 cabinet.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5310A.JPG

Front view, with CRT in place.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5311A.JPG

Rear view, with CRT installed.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5313A.JPG


CRT being powered by the CT-100 at the ETF, which had unreasonably low HV (first attempt, on Friday).

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5314A.JPG

Attempt #2 on Saturday, with CRT being powered by the Model 5 chassis. The Model 5 worked a lot better than the CT-100, but horizontal frequency tended to drift out of lock and we weren't able to get it back. Various things were tried in hopes of getting the Model 5 chassis repaired including replacement of caps and the horizontal frequency transformer, but were unsuccessful.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5315A.JPG

On Sunday we tried Bob's CT-100 chassis, but in the end we discovered that there is an issue with how much current the convergence electrode on the proto CRT is drawing out of the HV divider string in the chassis, which plays hell with the HV regulation. I will soon be modifying my CT-100 chassis so that the HV pot is no longer at the end of the divider string, but rather on the B+Boost line. This will ensure that HV remains steady, so convergence voltage is not chasing anode voltage anymore. Between this and some different value divider resistors (I bought a pair of 100 and 25 meg to try), I am confident I will at last be able to converge the proto CRT and get some decent screen shots. By the end of the day on Sunday we were all pretty tired...

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5316A.JPG

Nik,
I meant to ask you at the convention, but to determine if this is a fault with the proto crt or by design, how is the convergence voltage derived on the proto chassis?

Darryl

Same way it's done in the production chassis, though the values in the bleeder string are double what the CT-100 has. That's why I'm going to experiment with those parts, I have some different ones on the way right now. What I'm not sure about is if the convergence grid needs more current, or needs to be current limited by more series resistance. It was getting closer to being good with more voltage on it, but it also drew more current at higher settings. We tried to lower the value of the first resistor in the string (before the convergence pot), but it got very hot as it was burning off about 9000 volts. I'm still convinced that most of the problem was the ultor voltage drifting up as convergence voltage also went up; in other words, convergence always lagged ultor voltage no matter what we did. If I can get the ultor voltage to sit still while pushing convergence a tad higher, I think that will be a step in the right direction. That's the reason for tying the HV pot to B+Boost, rather than having it at the end of the bleeder string where its voltage supply (and hence shunt regulator operating point) can be influenced by current draw from the convergence grid.

I'll wait to see a picture on the tube. Very nice snag there. Make it glow.

Current limiting by more series resistance can only lower the voltage on the convergence grid. If a higher voltage produced better convergence, then you need less series resistance.

I think the problem with the test you did is that the convergence grid draws too much current when convergence is right, and that current is too much for the 19.5 kv supply to handle. I don't think returning the bottom end of the convergence pot will help. I think the only solution is a beefier HV supply.

If it were drawing an amount of current that was too much to handle, anode voltage would have sagged- instead it got higher. Only testing with the modified chassis will prove anything, Ed says the metal tubes were electrically identical to the glass ones...

If I understand the shunt regulator circuit, if the convergence grid draws more current that will shift the grid on the shunt regulator more negative allowing the HV to rise as you observed.

To minimize the effect the standing current in the divider would need to be larger, meaning a beefier supply. Otherwise you need to limit the convergence grid current, but then you won't have sufficient voltage for convergence.

John

If it were drawing an amount of current that was too much to handle, anode voltage would have sagged- instead it got higher. Only testing with the modified chassis will prove anything, Ed says the metal tubes were electrically identical to the glass ones...

If the convergence grid needs a much higher voltage, then the other possibility would be to move the pot further up the divider. Keep the total the same by reducing the resistance above it and increasing it below the pot by the same amount. The voltage drop due to the current drawn by the convergence grid will be smaller then, causing the anode HV to rise less.

John

Convergence is going to be affected by both the electrostatic convergence plates dimiension and positioning, the dimensions of the tube and the 2nd anode HV potential. The assumption is that the HV is to be 20kV.

Perhaps the HV in this prototype was only 15kV? The HV capacitor voltage rating suggested a lower voltage.

It would be interesting to know at least if static convergence can be achieved with the lower convergence DC potential of the CT-100 with a HV of 15kV.

Interesting point. I have always thought that even if the doorknob cap was rated at 20 kv and the negative end tied to the focus potential (2 kv) that there wasn't much margin if the HV was 20 kv.

However, the schematic we have of a RCA model 1, which uses the same tube, shows 20 kv as the HV. It doesn't make sense that they would reduce the voltage for this set.

The electrical specs for the earlier portotype metal tube is virtually identical to the later 15GP22.

The electrical specs for the earlier portotype metal tube is virtually identical to the later 15GP22.

I think Ed told Nick the same thing. If true, then it should just work.

I hesitate to suggest it, but perhaps there's a problem with the CRT.

That is one possibility, but another is the strength of the static convergence magnets on the proto tubes. The stick magnets on a CT-100 are very weak, and the prototypes had an entirely different system with 'wands' that could move in many different axis. If those magnets were stronger, it could account for the issues we're having.

Nick, I don't see how the permanent magnets could be a factor. If the prototype tube has specs very similar to the 15G, then it should work with 15G voltages, and apparently it doesn't. Since a 15G converges without the permanent magnets, using only the convergence control, the prototype tube should too.

The prototype tube is slightly shorter in overall length (about 3/16" shorter), which could mean the electron guns are at a different distance from the dot plate. If that is so, it could mean it will be a little different than a 15G. I should have the parts to experiment with by Monday, so I'll know more then.

Now that it has been suggested that the HV for this set's CRT should be only about 15 to 16kV, I wonder if now the static convergence will be achieved.

The lower beam velocity resulting from the lower ultor voltage should allow now enable static convergence?

I determined today that the chassis puts out 7-8 kv for the convergence grid with an ultor voltage of 16 kv. Nick can now try these voltages and see if he can get it to converge.

I also have the regulator circuit working in the range of 14-16 kv. With everything considered, I'm fairly sure that the chassis was designed for an ultor voltage of 16 kv.

Today I found a connection cut and a bad resistor in the negative power supply divider network. After fixing that and doing the alignment again, I now have working AGC and sync, plus proper gain for the IF strip.

Tomorrow I'll work on the reference oscillator.

16KV is pretty much the lower limit for the ultor voltage, with 20KV being the upper limit (for the prototype tube). The convergence G4 electrode is specified at 42.5 - 51% of the ultor voltage. You can do the math. :-)

The HV resistors for the convergence divider showed up in the mail today, I'm making the necessary changes to my CTC-2 chassis right now. I will try the 100 meg ones first, then 25 meg.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5328.JPG

Here are the changes required to remove the HV pot from the end of the convergence string, isolating it from any changes in convergence current draw. This should make sure that anode voltage doesn't jump around when convergence potential varies. Just lift the wire coming from the 50 meg resistor, move it to ground. Then take a wire from terminal 1 on the flyback (B+Boost), run it though a 2 meg fixed resistor, then to the open terminal on the HV pot. This arrangement gives you 420v on the high side of the pot, 270v on the low side. Pretty close to what I measured originally when it was still in the convergence string, which was 468v high side, 303v low side. During testing, the HV regulator works just like it should. I am able to adjust HV throughout its range from 20kv, to low enough to make the 6BD4 start redplating. For now, I left HV set at about 19kv. Tomorrow if I get some time, I will install the proto CRT and attempt to converge it with the factory 50 meg resistors in the string. If it doesn't work out, I'll play with the new ones. Here's what things look like right now in the cage.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5329.JPG

Steve reports the first attempt of getting video through the chassis, connected to a spare 15GP22. There's light on the screen, but some sweep issues have been encountered. Steve hopes to have these sorted shortly, and we might see some color images very soon.

Test setup.

http://www.earlytelevision.org/images/IMAG0004.jpg

With vertical sweep.

http://www.earlytelevision.org/images/IMAG0005.jpg

Without vertical sweep.

http://www.earlytelevision.org/images/IMAG0006.jpg

Very nice to see ongoing progress!

We have color on screen!

http://miniman82.4t.com/images/prototype%20color%20set/small/IMAG0037.jpg

Very encouraging!

Phil Nelson

Is this the protoyype chassis? Or, just the pix tube?
Looks encouraging....
What's causing waviness?
Is this the new color system, or the original to this set?
Looks very interesting.
Bill Cahill

You can read about the restoration here:

www.earlytelevision.org/rca_cpa_restoration.html

The waviness is due to ringing in the horizontal circuit because we are using a CT-100 yoke rather than the original. After I took that photo I was able to get the original yoke to work, and the ringing is gone.

This picture is NTSC. The colors are wrong, and we have a way to go to get it right. After the chassis was used for CPA it was modified to run on NTSC.

The next step is to build a CPA signal source and change the chassis back to CPA (not difficult). Then we will be able to watch CPA color.

Thanks. I had beren reading the thread, but, lost track some months ago...
Making cpa video amp: will it be hard to do?
I imagine you might have schematics for original one?
Didn't hat set have a bad flyback? If so, what did you end up using?
I'm fascinated with this set....
What are you going to end up using for a cabinet?
Was this with the original Pix tube, or, a 15GP22?
Bill Cahill

Bill, here are answers to your questions:

1. What has to be added for CPA is the circuit that alternates the phase of the color demodulation every field. There are two tube sockets on the chassis that were originally used for that purpose, and we have some hints of the schematic from a RCA patent. We will also have to install a 3.89 mHz crystal and retune the oscillator circuits.
2. No, the flyback is good.
3. The set belongs to Nick Williams. He has some ideas for a cabinet, but I'm not sure what his final decision is. My own thought is that the best thing to do would be to make a plexiglass cabinet so that people can see the guts.
4. Nick has the original tube, so I've been using a 15GP22. The specs for both are very similar.

I thought the flyback might be bad at first too, but I think it came down to the grid of the output tube not being tied to the correct negative voltage source. Once the tube was biased correctly, HV came up to 20kv and stayed there. Which brings up an interesting point: This chassis gives us the opportunity to document the operation of the pulse regulator circuit, I would very much like to convert another set to operate this way since it takes a little stress off the flyback.

We already discussed that the cabinet will be the TC-168 with doors, but I'm open to making a clear display case for it. Such a case would make the guts easier to see, though if you ask me it's pretty compared to production units. It definitely has a face only an engineer could love, if you know what I mean. In that respect, it is indeed a thing of beauty. :thmbsp:

I don't think that the regulator circuit would take any stress off the flyback, since it loads the flyback in order to reduce the voltage just as the shunt regulator does.

It's different than a shunt regulator though, since a HV shunt absorbs whatever voltage the CRT doesn't use to keep a constant load on the ultor supply. The pulse reg is different, because it modulates the input power to the flyback so theoretically the flyback should stay cooler if the demand on it (beam current) is low. In other words, the way I understand it if the HV needs to be lower, then voltage is shunted out of the primary. Seems that would be a lot less harsh on the fly than running it balls to the wall all the time.

I was asked recently to provide shots of the proto set in it's cabinet to use as part of an article, so I thought I'd share the same photo here so you can all see what the set will look like once finished. This is the TC-168 cabinet with doors, in oak.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5522.JPG

That is some great news Steve, passing video and getting sweep is an accomplishment, can't wait to see everything as it should be with this set displaying CPA on the proto tube!

Nick,

The set will look great in the cabinet!

Mmmkay,


I finally had some time to fool around with the proto tube, powered by my CT-100 chassis. I mounted the stuff in the cabinet same as at the museum, then powered it up. Luckily, the tube rim doesn't get close enough to the chassis to arc over with the chassis in the cabinet. :smoke:

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5558.JPG


I found that I have the same issue with not being able to achieve convergence, despite the HV pot mod being done. I confirmed that ultor potential is not dancing around, even with the convergence control maxed out. In this shot I haven't really done anything with the static magnets, just powered it up and played with the DC convergence control. Same as at the museum- you can get close, but not close enough. This is with the 'stock' 50 meg string resistors installed in the chassis, next I will give the 100 meg ones a try.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5559.JPG

getting there!

Yep. The glorious "End" is in sight...

Wow you're really making excellent progress with this TV, it is so cool to see colour on the prototype tube, fantastic!!!:D Keep up the excellent work!!!:D

I'm very impressed with the work. How far is the original chassis?
Though the colors were wrong, you have color. Isn't that the CT-100 chassis? I get mixed up which chassis you are using... Sorry, guys....
But, my hat is off to you experts. Great job....
Bill Cahill

The 100 meg resistors only made the situation worse (as expected), there was even less convergence voltage available. Ohm's Law wins again. Then I tried a 25 meg resistor as the first one coming off the ultor going to the DC conv. pot, and bingo it popped right in! Unfortunately dropping so much voltage is causing it to heat up in a hurry, so voltage drops as time goes on. I've decided to order five 5 meg resistors at 2 watts a piece, which will give 10 watts total dissipation. This will spread the voltage out over more resistors (and thus more surface area), and hopefully cure the drifting issue. Once I am able to keep the convergence voltage stable, I will finally be able to post properly converged pictures of the proto tube. Here's where I'm at right now.

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5561.jpg

As you can see, blue is still slightly high and red is a little displaced as well. These are static convergence issues, which are easily cured by twiddling the magnets on the neck of the tube. Ignore the faint blue bar at the far right, I think the tuner is receiving interference from the stray static field escaping the CRT. I will need to construct a supplementary shield, to make sure all the ultor potential remains trapped. Heavy plastic should work. Yay progress! :thmbsp:

Beautifuller and beautifuller!

It looks great for a 60 year old Prototype tube that probably wasn't intended to last a year.
Strange to think that probably everyone who worked with it back then is most likely gone by now.

Nick, how about trying a 25 meg on both ends of the convergence pot followed by a 50 meg to ground? Mouser has 1-watt 25M HV-rated resistors, but none with higher power ratings. I used two of their 50M 5-watt ones in my CT-100 and they work well, even fitting the cup on the HV rectifier socket.

Wow, you are really succeeding in bringing this tube back to it's former glory, keep up the great work, those colours are looking very good and very accurate!!!:D

Amazing Proto metal/glass CRT holding orig vacuum!

Nick, how about trying a 25 meg on both ends of the convergence pot followed by a 50 meg to ground? Mouser has 1-watt 25M HV-rated resistors, but none with higher power ratings. I used two of their 50M 5-watt ones in my CT-100 and they work well, even fitting the cup on the HV rectifier socket.

I was going to try that, but Ohm's Law tells me it's a bad idea. Reducing the resistance on the low potential side does a couple unwanted things. #1 it drags the low potential side of the pot down, which is counter productive (I need higher voltage). #2 it increases the total current drain of the string, placing added stress on the first resistor causing it to heat up and drift more than it already is. With a 100 meg as the second one, the low potential side of the pot is pushed higher. Total current drain is reduced, taking stress away from the other ones in the string. Here's a comparison chart, with 25 meg for both and on the right the way things sit right now.

http://miniman82.4t.com/images/prototype%20color%20set/small/resistance.JPG


In practice there's less voltage available at either end of the convergence pot, because of the first resistor drifting. About 10kv and 8kv respectively, by the time I measure it. So as you can see, it's beneficial to dissipate the majority of the voltage after the convergence pot.

OK, I think I misunderstood the original configuration. I thought it was originally HV>50M>pot>50M>(followed by HV pot or ground depending on the mod you described elsewhere), as is my CT-100. I had intended to propose HV>25M>pot>25M>50M>(ground or HV pot, etc.). You are already at 125M total not counting the pot, so now I understand the problem is mainly the 25M resistor's dissipation, not the total string resistance.

I have very sad news to report: the proto CRT is dead. I don't know why this happened, it was in operation a few days ago. I came back from Beloit this afternoon and turned it on, only to be greeted with crackling sounds and no picture. Sliding back the neck stuff revealed white getters, and a crack nearly all the way around near the base. This means there's no more proto CRT's left working in the world, and it will be a long time, perhaps never, that one will be seen in operation again. :sigh:

http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5791A.JPG
http://miniman82.4t.com/images/prototype%20color%20set/small/IMGP5792A.JPG

Damn ! Might have been a manufacturing defect that just finally manifested itself...

Aw Man that really, really sucks, sorry to hear this news...:sigh::tears:

I'm gutted, I can only imagine how you feel. So sorry Nick.

Oh man, this is terrible news!
We can only guess what went wrong, being a Prototype it was probably run off in a hurry with no thought to it's longevity.

Thankfully we at least got to see it (and document it) operating before this happened.

I wonder if that darker area was the fracture origin point, being on top it would have had the most heat, and stress.

at least we had it once.sad ending to a great set and a great series of posts

Nick,

How sad to see this happen, although it was great to see the picture on it that you did capture of it working properly.

I felt privileged to see it at the ETF, and also privileged to help u that little bit of soldering I learned a lot watching you guys work on it.

Matt

The only thing I can think of that might have gone wrong is a hot spot on the glass, a consequence of building the tube incorrectly to begin with. If the flames are kept on the glass for too long during an operation like neck welding, the glass becomes very brittle and subject to fracture. This can be seen with a polarimeter, the glass will have a blue band around it. Can't be sure what the cause was, since I hadn't done anything to it between the time it was last used and now. It just sat up here in the apartment, no one even touched it. I suspect this is a fatigue fracture, caused by repeated heating and cooling of the area around the weak glass. The heaters were supplying the heat, and it looks like it gave way at the hottest spot- right above them. If RACS can rebuild this, it would be a simple job. Just neck glass and a gun, but I hesitate because dot plates have broken in the past and these are more fragile than a 15GP22 because the internal structures are different. A 15GP22 has a lightweight frame holding the mask and plate in alignment, and because it's light it gains or looses heat relatively fast. The proto tubes on the other hand have a heavy metal block between the dot plate and mask, meaning they have much more thermal mass. I will have to ask Filipe what he thinks about giving this a go, it's a long shot at best.

Wow, that really sucks. Sorry to hear that miniman.

I am sad to see this news. I wish you good luck with the rebuilding possibility.

OMG! That is the crappiest news I've heard as far as the tv hobby is concerned. It had such good emissions too:tears: I wish I could have seen it working more, I was sick last week with a sinus infection or I'da been over. Crap, I hope you can get it rebuilt at least.

I wonder if this is related to the convergence problem. Maybe there was a very small leak that still allowed the tube to have emission but messed with the convergence?

I am very saddened that your prototype tube has cracked and gone to air, especially the fact the tube was finally up and running displaying good colour pictures :(, if something like this happened to me with my projects I would be weeping buckets!:( Knowing RACS having successfully rebuilt a 15GP22 and there being possibility they can do the same with your prototype tube gives some ray of hope and I do hope after your discussion with Filipe it will be agreed that it will be feasible to try getting the prototype tube rebuilt. Anyhow despite the sad news, it was really good that you brought this tube back to life while it was in working condition and got it to display excellent pictures! Anyhow best of luck with whatever possibilities there is to get the tube rebuilt!

Bummer for sure. :sigh: But thankfully it was slow enough lose of vacuum to not launch the gun assembly forward. Hopefully RACS can rebuild.

Did you leave the air conditioner on
for the weekend? With all these temperature extremes we've been having, it's little wonder other failures aren't occuring.
Third floor apartment and all!

That's dreadful news, after you had made so much progress with this unique set.

I suppose there's no sure way to predict or prevent such a failure. All the more reason to enjoy these sets while we can.

Regards,

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

I'm sorry to hear about that.. I'm going through nightmares myself with Picture Tubes..

How weird.

Even here in San Diego (no real extremes...just been a bit warm and humid).... I suddenly have "jeeees...this was fine last week" issues with the Sony 301 AND the Sony 305. Mine are simple instability issues. Not anything like this catastrophic thing :-(

So sorry to be reading this. It certainly was exciting to see color on it!

This is just so sad.... Sorry to hear! :(

jr

PS: a glass expert may be able to read the "ripples" in the crack and determine the starting point... just like ripples in a pond.

Right, the fracture can tell you a lot about how the failure manifested. I actually used to do a lot of that kind of thing in aviation, since I was part of an emergency reclamation team. It looks to me like it began right at the top where the heat was at its strongest, then propagated around the rest of the neck. I will send pictures to Filipe later this week, asking his opinion.

That's a darn shame, considering the effort put into the set.

On the other hand, if you had acquired her a year later you would have never made the progress that you did. One thing working in your favor is your relationship with RACS - I hope they can do something for you.

Ouch! What a terrible, random thing to have happen. It is so sad to see it happen to something so historic on top of that. I almost can't believe the news...it feels like only yesterday that I saw it come to life for the first time in ~60 years, and now this.:sigh:

I hope that the RACS repair idea is successful.

It could be the heat wave.....one of the replacement PS doubler caps I installed in my Silvertone roundy almost 2 years back went bad 11 days ago, and that was a fairly robust part! The year before I left the air conditioning off during vacation and returned to find one of the plastic feet on that same set had shattered despite the set being left otherwise undisturbed.

It might be a good idea to add some fans to the set if you ever get a good CRT in it again.

Life sucks sometimes.......

miniman,
What an unpredictable event this is. What could anyone do to prevent this tragedy?
Nothing I'm sure. It's a crummy outcome to a noble undertaking.

This is a very sad news... :sigh:

I've been following your progress, that is really a rotton event that should have never happened. Would have been great to see it to the end. I've got a CTC 10 and 11 and I really enjoy them to the fullest. Love the old Tv shows on them. I use both daily. Hope you can find a tube to at least keep it going. Good Luck.

Tom, Nick has been working with a CT-100 to power the prototype tube. I have his chassis in Ohio, and have been using a 15GP22 with it. Work will continue on the prototype chassis with a 15G, which will work just fine.

Damn shame. Best of luck with recovery efforts.

That crack in the neck of the CRT makes me wonder if it was thinner than later production tubes?

It's still a crying shame, though, that it went to air just after you got fairly decent color bars on it.

Bruce

What else could I say? Thanks for sharing what you have done.

So far I have had a 6GH8, 6JE6 and 21FJ crack and go to air after returning a retired set to service. None of these tubes were being touched, they just went to air while the set was off after I started using the set again.

So far I have had a 6GH8, 6JE6 and 21FJ crack and go to air after returning a retired set to service. None of these tubes were being touched, they just went to air while the set was off after I started using the set again.

I suppose Glass ages just like anything else, maybe after 50 or 60 years minor flaws become fatal flaws.

And I too have had tubes crack after lengthy power off. The CTC-9C that I have had a cracked audio output tube, I think, 6AQ5. Had a 7591 crack and give a really nice purple show as the air leaked in. Now THAT was an expensive tube...

I guess I've been lucky, I've never had a tube go to air. I've found a few in sets that I picked up but never while I've owned them. I better go knock on wood now. I just looked behind me and the CTC 11 that was dropped down the stairs is running in the living room. I use it every day....:rolleyes: I woke it up from a very long sleep.

I knew you would get that one going,Mark.