21CT55 Restore "Plan B"
 

I have an RCA schematics book that covers all chassis from CTC2 thru CTC20. I zeroed in to each schematic and examined just the circuitry from the HOT thru the FBX to the output that the FBX drives. I was amazed at the lack of similarity of all their horizontal driver circuitry! It was like each year RCA had a contest among its engineers who could make the most circuitry changes from last year! This convinced me that hobbling in a look-a-like FBX from another RCA into my CTC2B was impractical and injurious to my or any other person's mental health. I am even more convinced that John’s approach of replicating the original FBX on his pro coil winder is the only way to go.

However, I will entertain the swapping-in of a different RCA FBX into my CTC2B as a far-out “plan B” backup. Has anyone in this forum performed this swap or knows of any successful swap on a early delta-gun, magnetic converged roundy? Also, are there any RCA CTC4 thru CTC20 FBX available out there, NOS or used, besides the CTC20 at Moyer?

OTA NTSC Picture Quality
 

Although my only roundy is a non-functional 21CT55 and I didn't watch the Rose Parade in SD or HD I still feel compelled to comment on this year's Rose Parade screen shots. The OTA screen shots on Bob's thread so far have been mostly taken from premium CTs which conform perfectively with NTSC WB IQ standards. These roundys were undoubtedly driven at their antenna terminals with quality ATSC to NTSC converters. It seems a shame the "pure restoration dictate" precludes chassis modifications which permit direct external composite video inputs at ther first video amp inputs. How many forum members are using ext-video to evaluate their CT's ability to properly demodulate composite video and process it to the CRT without the degradation of marginal RF tuner and limited bandwidth IF amplifiers?

My CTC2B chassis is not constrained by the "restoration" consideration and has never processed the deceased NTSC RF/IF programmed inputs. It has always performed as a pure composite video monitor, driven from DVD, Laser Disk, S-video VCR, C-Band Big-Dish and 4DTV Digicypher. At the time of its flyback meltdown, I was in the process of modifying it to accept Component Video which should extended its baseband luminance and chrominance to a full 5mhz or 400 lines vs the 3.3mhz or 264 lines of NTSC Composite Video. Now if only I can get a replacement flyback that would converge as good as my original CTC2B, I can proceed.
Tom

George Stevens Winding Machine
 

John,

I am looking for gears and cams for a George Stevens 225 winding machine, can you help? I noticed a previous post with a picture of a gear and cam assortment. I have the same picture I was wanting to know if you know of any one with any of these gears and cams? I am in the process of trying to purchase some. Let me know if you can help or know of any one with gears and cams to sell.

These are the parts I am currently looking for:

1. Driver Gear - 37
2. Driven Gear - 76
3. Cam - .75
4. Idler - 1
5. A-115-T A series driver gear
6. A-111-T A series driven gear
7. Z-.600 Z series cam
8. 1:1 idler cluster
9. A-691 wire guide arm
10. A-697 nylon wire guide wheel
Thanks, Have a Happy New Year!

Ken Wyant
Current Controls Inc.
353 South Brooklyn Avenue
Wellsville, New York 14895
Phone: 585.593.1544
Facsimile: 585.593.1713
"E" mail: [email protected]

Ken, email sent. Long and short, I do not have any spare parts. George Stevens Co. still has some gears and cams available, but they are expensive. The gears for the machine are non-standard, so are not available from the usual gear sources.

First Signs of Life
 

Just finished installing the new FBX sub-chassis circuitry into the CTC2B chassis. No dynamic conversion, chroma keyer, color killer, chroma blanker pulses from the FDX are connected. Focus out of range, linearity, screens, gray tracking not adjusted.

Power input is 115vac, B++ adjusted for 378v producing 860v boost, Ultor is adjusted at min of 28kv, max is well over 36kv! HOT cathode reads 128ma. The big ultor voltage with a tiny HOT current indicates I need a HOT that matches this new FBX, namely a 6JE6A replacing the original 6CB5? I have to order one and its socket & cap.

The premature screen shots indicate I’ve got a long ways to go on this one to approach this 21CT55's previous posted shots.

...

Read from where, the fuse like last time or an actual current reading from the tube cathode? 6JE6 is a stout tube, heavier duty than the 6CB5 (higher max ratings, anyway). I personally don't believe you're getting 30+kv at that cathode reading, unless you somehow stumbled on a combination that works better than RCA originally came up with.

If you really do want to get a better picture out of this thing by toying with the HV supply, you need to make it 'stiffer'. The electronic equivalent of horsepower vs torque, if you get what I mean. In other words, you need more current and better regulation, not more voltage. To do that you would need a flyback capable of delivering that current, or a pair of smaller ones. Then you would need a way of controlling the extra power, which would mean a pair of shunt regs. Or a better solution: heavy duty flyback, and forego the shunt style reg in favor of a feedback type of thing. Something like an extra winding on the flyback which produces a voltage which can be used to control the drive (like the GE portacolor).

This is where I get lost... Usually..

I mean I kinda get it but....
Im stumped.

What's not to understand?

Thanks for Your Replies
 

Andy...Yes, there are two rectifiers: the one closest the FBX is the focus, the other is the EHV ultor. There is no voltage doubler, I removed it.

miniman82...I stated "HOT cathode reads 128ma" This was 128mv across a 1 ohm resistor inserted into the normally grounded HOT cathode.

You stated...."If you really do want to get a better picture out of this thing by toying with the HV supply, you need to make it 'stiffer'. The electronic equivalent of horsepower vs torque, if you get what I mean". Sorry, I don't.

My objective with this "resurrection project" is to get my CT2B operating with the minimum amount of circuit modification, not "toying" around to create the Vintage Color TV Version of Cold-Fusion!

freakafta8....I'm with you!

Hi, Great that the flyback enables a picture. I may be wrong, but I seem to recall that a 6JE6 is a 6DQ5 with a different base, having very similar if not identical specs. I'll look at my RCA tube manual later and compare the two. If that's the case, you can just plug the 6DQ5 into the socket with no mechanical changes.
Looks really good so far!
Kevin

They're Samo!
 

Hey stromberg6......You're right on, the 6DQ5 and 6CB5 are electrically identical! The local elect store has them for $22. Mechanically its perfect, all I have to do is interchange the 2 grid pins with the 2 screen pins. In fact RCA used the 6DQ5 with my new FBX thru CTC12 then switched to the 6JE6 in the CTC15 with the same FBX. If this doesn't calm the ultor out of the mid 40KVs, I'm at a loss.
Thanks a lot......Tom

I remember in the later days of the roundies and even after RCA had the HV rectifier drop into the top of FBX. Many of those fried because of dry or contaminated dielectric grease or loose cage screws. Out of scrap I had used a CTC-11C FBX in a CTC-16. My earliest experience with roundies was with a CTC-7. If your chassis uses a 6BK4 shunt regulator I would imagine a later xformer could be used with a little circuit modification to make your set functional. Question; What CRT do you have in that thing? It looks to be a glass bell. If I remember correctly the 21AXP22 was metal.

Your welcome Tom. I just looked at the RCA manual, and the specs for the tubes 6DQ5 and 6JE6 for practical applications are identical, only a few minor differences, and the 6DQ5 looks like an excellent sub for the 6CB5, but for the connections at the bases. Interesting that the pin outs are different, perhaps to prevent quick swapping, protect patents, or to generate service revenue when uninformed techs subbed one for the other lol.
Let us know how the swap works. Hope it all comes together the way you want.
Kevin

FHX Ehv Rect and CRT
 

doogie812.........The FBX I'm using was intended to have the EHV rect on the top of its HV doughnut. Any loose fit would produce a continuous arc that could take the FBX out. The CTC2B FBX had a HV lead and tube cap. I cleaned all the HV grease out and removed the little hooky spring. I then quickly soldered a tined spot on the large output contact area and tack soldered a EHV rated lead wire and cap going to the original EHV rectifier. I then completely filled the output cap cavity with RTV silicon. Works fine, but at an occational 40+kv non loaded run with no 6BK4 reg the little 3A2 EHV rect arcs across its full 2in length. Im using my original 21FBP22A rare-earth gray screen I installed in place of the 21AXP22 in '64. This is the last and IMHO the best roundy CRT. RCA rates it's ultor at 27.5kv and their data sheet states "Brilliance and definition decrease with decreasing ultor voltage".

:rolleyes:

And what are you hoping to accomplish by doing that?

Again, you need to stop misquoting the tech sheets. 27.5 is design maximum, not a 'rated value'. Here's a link to the PDF: http://frank.pocnet.net/sheets/049/2/21FBP22.pdf

Any time you operate the tube beyond it's deign center values (found on page 4, which clearly state 20-25kv), you open yourself up to excess x-ray production, and an increased instance of electrical shock or tube destruction from arcing. I caution anyone on these forums from doing anything you're attempting here, I feel it's unsafe on a number of levels as you've already demostrated by destroying a flyback.

Ah Da......
 

Since I was replacing the original CT2B FBX circuitry with the entirely different FBX circuitry from a CT almost 10 years newer, I had to know how high the ultor EHV would go if the CRT was at cutoff and the 6BK4 HV reg would suddenly burn out. Surly this makes sense, even to you??

Back in the day it was normal to run these tubes 21FJP22/FBP at 25kv. 20 to 24 would be on the low side.

Same thing as any other HV section, voltage goes through the roof.... On my CTC-9, anode voltage shoots up to around 28kv without the 6BK4. But that's common sense, no? Shunt regs are pretty rugged though, why are you worried about burning one out?

I thought so… Since you are using a glass tube you can nix the HV capacitor. Glass has a dielectric constant of 1. Doogie

Make sure the dag is grounded.

FBX Boost Circuitry
 

Since my CTC2B FBX failure, I have attempted to replace it with a “modern” roundy FBX used in the CTC 10, 11, 12, 15, 16 and 20. The support circuitry for this FBX is totally different from the original CTC2 and CTC2B I’m familiar with. For starters, none of the CTC10 and later have width controls and must rely on component tolerance to assure proper overscan. They incorporate a balanced pair of windings with a 10ohm wirewound pot to center the raster +/- 2in. Even the crucial damper circuitry is totally different, using an ferrite-cored vari-inductor and capacitor values to accomplish horz linearity adjustment with an “efficiency control” that performs some sort of resonance?? All of this design rational is unfamiliar to me since my only TV reference ends with Fink, 1957.

In my present FBX test-bed module, the vari-inductor has no effect on anything over its full range, not good. I have the wrong RCA coil part number but have ordered the correct part, got to wait till it gets here. Horz linearity is very poor and the EHV Ultor will climb well past 40kv, resulting in severe arc-over of the little 3A2 EHV rectifier. With almost all post CTC10 roundys using this FBX with many circuit variations, surely some members have experience with these “modern” FBX configurations. All replies welcomed……Tom

FBX Replacement Status
 

I am attempting to replace my unavailable original 21CT55's CTC2B FBX with an available CTC11, CTC16, CTC20 FBX. The new TV's horz oscillator and FBX support circuitry is completely different from the original CTC2B's. The only part that seems to be the same is the yoke. Progress so far has been encouraging. With 115vac mains, I get B++ of 396v, 170ma at the fuse, 170ma at HOT cathode, and a Boost of 840v with a minimum Ultor of 27KV. I use the new FBX to deliver chroma burst keyer and color blanking pulses which generates good chroma channel performance. Only vertical dynamic convergence is presently operating, horizontal is non operational since I still have problems with the display's horizontal fold over. No sense working to align horiz convergence until I fix the fold over.

I'm officially calling BS: there's no way in hell you have only 128ma on an output tube making that much high voltage from the flyback, it's simply not possible. You're fooling us and yourself if you think you have the right reading, I promise you it's a LOT higher than you think.

Nice job of circuit re-engineering / design.
From what I can see on my crappy old crt monitor you are almost there. The color looks exceptional, tweek the horizontal and you are home free.
For me I wouldn't get obcessed with voltages, currents, et cetera. The picture displayed tells just how close you are.

I think miniman doesn't like you. thats what i feel.

By that metric, I guess I should have ignored the 260ma current I first saw on the CTC-4 when I first powered it up. After all the picture seemed OK, and it's not like I can't just walk down to Radio Shack if I blow the flyback. :lmao:


I don't care what Tom does to this set Bates, it already lost it's historical value when he smoked the flyback. I'm more interested in what other people are getting from Toms 'work'. I just don't want people to take anything from this thread and use it on another set, because it would be extremely dangerous to do so. 27+kv at the CRT? No bueno, plus there's just no way he has 128ma HOT current while doing so. I can promise you that all 3 of my sets would be at easily twice that value if I tried the same thing, so either he's reading it wrong or telling us the wrong number.

This badmouthing is getting annoying. I'd urge everyone be respectful to those who post here. Calling someone's post BS has no place here, when the intent of Tomcomm is clearly to get help from the collecting community in dealing with the failure of his flyback.

No sympathy from me, it's clear why it failed in the first place... It's not disrespect, it's the truth.

As I already said, I'm most interested in others not being mislead. He can do whatever he wants to the set, I don't think I'm being disrespectful for saying that. I simply want people to be HONEST with their assessments, that's all. Telling us there's only 128ma on the cathode is misleading, and to the uninformed observer, irresponsible.

Let me illustrate: what's the lowest cathode reading any of you have seen on your sets? Lowest I ever saw was 178ma on my CTC-9, and it took a LOT of tweaking to get there. Most would be happy with 200...

miniman82, there are many reasons he may have come up with 128ma other than an attempt to mislead people. There may be problems with his test equipment, he may have made an error in how he took the measurement, or it might be because he is using a flyback that was not designed for the set.

I still say you should tone down your talk, and stop accusing people of misleading.

I'M NOT YELLING AT ANYONE.

Anyone who knows me knows that I'm a very easy person to get along with, just ask Mark. Sometimes it's hard to get meaning through some words on a screen, that's what's happening here. I call things like I see them, but sometimes people take it the wrong way. I'm used to it, doesn't bother me anymore. Why are people so touchy-feely anyhow? It's not like I'm threatening anyone...

For the 3rd time now: I'm simply pointing out that there's an obvious lack of hard facts here, and it would do everyone here a lot of good to know what's really going on. Most of all is Tom- I of all peple don't want to see him burn this thing down a second time, but I'm telling you all that is exactly what's going to happen if he doesn't figure out what his HOT current really is. Is that not a good thing, or am I being disrespetcful still?

May I suggest instead of saying "I'm officially calling BS:" say, "that can't be correct"

Instead of "there's no way in hell you have only 128ma on an output tube"
try "your readings may be in error."

Offer some advice on how to remedy the problem instead of calling him a liar.

You have been on his case for Hot Rodding his set since the first post.

It is hard to convey tone through text but a few less inflammatory words would help.

I didn't hear it mentioned (or might have missed it), but was the OP using a digital or analog milliameter to measure HOT current? As digital meters are known to go nuts in applications involving high level pulses and waveforms, I sure as heck would use only an analog meter there. And I would do it at the cathode, not the B+ fuse.

As for another poster's statement, "For me I wouldn't get obsessed with voltages, currents, et cetera. The picture displayed tells just how close you are."

Yeee-ikes! That advice might pass muster with B&W. But with color, it is absolutely critical that the HO cathode current be kept within spec or lower. Even with the later 6JE6 and 6JS6 (in Zeniths) we would strive for no higher than 210ma to give the tube and flyback a reasonable chance of survival. 200ma was ideal if width and regulation were adequate. Bill(oc)

i agree that sometimes the comments get a little offensive.you might be the greatest guy in the world but when you get in front of the computer, a new personality immerges.i found toms postings to be informative and enlightening.if he misquoted some info or in your opinion,to be wrong,then you dont have to be insulting.also,no need to get upset with anyone in this forum.these guys will help you in ways you cant imagine.outside of a few,they are friendly and courteous.reading posts from people arguing is just like being married again.dont want to hear it or see it.as i am an old timer who worked the wrestling business,i watch mma,boxing,some wrestling,etc.i come to this board to learn and relax.maybe if you folks want to argue and fight,send private messages?thanks for letting me post and everyone ENJOY this wonderful forum we have while we can!

Well said, Ron. Pm's are a good idea for stuff like this.

...and what we're forgetting here is that where it not for the fact that he did anything with the set, most of our 'YL's would have had the set carted off to the landfill to get it the "hell out of the garage" to make room for gardening supplies.

The fact that someone is trying to do two things:
1. *Learn* something about the design and the components' capabilities,
and
2. Move forward with assisting in the reproduction or replacement of what would otherwise be an unobtainable part, knowledge of which will benefit each and everyone in the hobby.

..should be commended.

I don't think we'd be having anyone in the commercial world research the production of tube circuit flyback transformers.

Heck, I can't even get someone to rebuild or even supply a CRT that there were at least 100000+ built by Zenith in the day, and I've posted requests on nearly every forum on the interweb over the past three years. And to boot, the tube I need is sought after by the owners of what is at least 10^4 more sets than number of 21CT55s bulit in the first place.

Move on.

We will all benefit when the "art" of winding new transformers is perfected (rediscovered), just as we all benefit when a number of 15G's were used in the development of a rebuild procedure.

HOT Current vs Fuse Current
 

Seems the latest miniman issue relates to my posting of 01-29-11, 02:44 PM. Since RCA connected the 6.3vac heater ground to the 6CB5 HOT cathode ground they obviously didn’t want Service to measure HOT cathode current. Sams detailed service procedures made no mention of measuring HOT current so I have always measured FBX system current at the HV fuse. assuming this was a good approximation of HOT cathode current. The 128ma Hot cathode reported in the post was made on a DMM which was obviously wrong.

When miniman delicately suggested this reading was suspect, I remeasured with an analog VOM and surprise! I got the exact same current at the HOT cathode as I got at the HV fuse, both were 170ma, quite modest for well over 27kv ultor, right? I immediately edited my original post and gave the edit reason “Corrected some measurements”. There never was an attempt to fool myself or irresponsibly mislead the rest of you members as was stated by miniman.

---

I seem to recall reading in RE magazine a long time ago that High OR LOW current in the HOT ckt is bad, somehow, if the current is too low it STILL will "throw things off balance" and cause heating n the FBT. Remember...we ARE dealing with a "tuned ckt" here, a little off either way can cause problems.

And 128 MA. where 200 should be is WAY off IMHO.

...