I originally posted the following message on May 30, 08 when my 21CT55 seemed to be performing at its best. It gave me the opportunity to rationalize why I did not restore it to original, since I destroyed the cabinet in making it into a table model to save space in my garage workshop in 1964........................


.................I decided in October 2007 to reactivate the beast after 40 years in attic storage and use it as a test bed to determine and demonstrate in photos, the picture quality this 55 year old RCA CTC2B chassis was capable of producing. As such, it was not constrained to replicate the original circuitry in every detail or even operate to the '55 RCA spec. I jacked up the +400v B++ supply to above +420v with silicon diodes and got a horz boost of almost 1KV. I intend to start reducing the CRT Ultor HV from its present 34KV to the 28KV range while doing a full convergence at each reduction level to determine if I loose ANY picture quality.

Since I'm running the 21CT55 as a composite monitor, I disabled all the tuner, RK/IF and audio portions and opened all unnecessary tube 6.3v heater strings to allow the power transformer to run much cooler. I left all inactive tubes in their sockets and documented all changes for immediate reactivation. Yes, I brutalized this valuable historical item but there are at least five other 21CT55 restorations on this forum alone. I believe I've succeeded in my goal of demonstrating the 21CT55's ability of displaying exceptional picture quality.

http://s677.photobucket.com/albums/vv134/tomcomm/55%20RCA%2021CT55%20TV/

I do intend to refinish the surviving front panel of the original cabinet using the approach described by Bob G in his impressive restoration. I might even attempt to construct a pseudo pencil-box control panel,

On March 21, 2010 at 3:30pm my 21CT55 ate its flyback transformer in a cloud of acrid smelling white smoke coming out of the HV cage! I was out of the room for about 10 minutes so I didn't see it loose its picture and couldn't shut it down, so it just cooked. I was so shocked, I just killed the power without looking at the HOT and damper to see if their plates were red hot. I opened the cage and the FBX was still smoking. The HV doughnut was dropped down and dripping hot insulation stuff, a truly sickening sight. The B++ fuse had not blown because it was 1 amp! It should have been .5 amp since the running current was only 265ma. I checked my fuse box marked .5 A and the 4 remaining fuses were all 1 amp, bummer!

I lifted the doughnut back to where it should be, supported it with pieces of foam plastic and let it cool off for about 30 minutes. I put a current meter in series with a .5amp fuse and applied power. Remarkably, the boost voltage and B++ started to slowly climb and the picture came on as the current settled at 265ma, boost reached 780v, ultor was 27kv, all normal! Naturally, I was delighted. After about 5min,the screen went black, the current climbed to 480ma and the boost dropped to the B++ of 420v. The HOT plate started to glow so I shut it down. The FBX was warm. I pulled the damper, the yoke and all the HOT and rectifier plate caps and power up'd. The HOT grid had a normal 150vpp drive input, that was not the problem. All FBX windings measured nominal resistances, maybe they developed shorts? Anyway, I needed a CTC2B FBX, apparently a non obtainable item. So was this the end of my 21CT55?

Do any members have an operational CTC2B flyback transformer or know where I can acquire one? If so please send me a PM with details ......soon. Thanks, Tom

'ONLY' 265ma???

If any of my sets ever got that high, I'd pull the plug right away. Hell, I'm not happy with the 210 my 7 is at right now. You played with fire, and got burned. I don't think anyone will be willing to toss another unobtanium part your way, not with the kind of experimentation you've been doing. Just my opinion...

:tears: Sincerely saddened to learn of your misfortune. Hope you can find a flyback to repair that amazing set. I've enjoyed the many pictures you've posted of that set and the Sony monitor. The comparisons were jaw-dropping to me.
All the best!
Kevin

bummer - from the photographs you have posted that set produced an absolutely amazing picture
just a thought - since the set is heavily modified already, are there any flyback transformers for other sets that are close in specifications to the original? i know the ctc-2 and 2b chassis' are somewhat unique in their design - but i would think there should be something close in the early RCA line - hell there may be something in the 60's or 70's tube driven or SS sets from other manufacturers that are close in specifications - certainly no real need to keep it original -

BTW - i know where there sits a roundie that i have been thinking about snatching and doing just what you have done to the 25ct55 - improving it exponentially - with a few modifications - i know the purists will get up in arms - but hells bells it is just an old television - it certainly isn't like painting a moustache on the Mona Lisa

miniman82, are you talking about HOT cathode current or current at the HV fuse?

HOT cathode, I'm not aware of any current specification in any manual that tells you to read the HV fuse... It's not in my RCA manual, anyway.

Yeah, but the way I read it, I think that is what he was measuring. I could be wrong.

The first replier to my thread seems to consider himself the VK Safety Nanny and member attack Pit Bull. Has he considered getting professional help with his obvious anger management problem? Just my opinion..............

That said, my normal +425v current of 265ma is always measured across the HV cage fuse clips. RCA requires a 300ma fuse so the flyback is well protected. I usually use a 500ma fuse since I couldn’t find a 300ma item but accidentally used a 1amp fuse when the flyback cooked so it didn’t blow. This wouldn’t make any difference since the flyback shorted and was doomed.

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. This simple and logical change raised the B++ from 392v to 425v or 8.4%, well within RCA’s safety margin. How many members performed this same “experiment” on their sets??

The first replier to my thread seems to considers himself the VK Safety Nanny and member attack Pit Bull. Has he considered getting professional help with his obvious anger management problem? Just my opinion..............

That said, my normal +425v current of 265ma is always measured across the HV cage fuse clips. RCA requires a 300ma fuse so the flyback is well protected. I usually use a 500ma fuse since I couldn’t find a 300ma item but accidentally used a 1amp fuse when the flyback cooked so it didn’t blow. This wouldn’t make any difference since the flyback shorted and was doomed.

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. This simple and logical change raised the B++ from 392v to 425v or 8.4%, well within RCA’s safety margin. How many members performed this same “experiment” on their sets??

Sorry to hear the news. I don't know the #2 postor, and I wouldn't have said that myself. In my viewpoint, this hobby would be zero fun without any challenges, and this is no different from a situation where someone might restore a '38 Cadillac, and take it out for a Sunday drive and have a kid run a red light or something. It happens.

There are several AKers with 21CT55s, and hopefully someone will speak up with a good FBT. If not, I'd suggest doing some comparison research to see if you could use a different Fly in that set. After all, the basics are the same for the horizontal frequency and deflection angles, etc., among most all 21" color sets. With a little qualIfied engineering, I bet a later model FBT could be used, since your set is a working demonstrator and not a virgin timepiece.

Charles

Am I understanding correctly that u used your apparent vast knowledge to experiment with a virtually priceless object that being the flyback? If so... shame on you!
If you took that flyback to it's limits you ought to be forced to restore it by chemically softening the coil so you can unwind it in order to determine exact length and specs for the new windings you will replace by hand. After you spend countless hours doing that maybe you will learn your lesson to respect things properly. All the knowledge needed to get the most out of those TV's has been uncovered by many great men here at Videokarma.

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. ... How many members performed this same “experiment” on their sets??Sorry to hear about your fly problem Tom. Does that mean your quest to engineer an S-video input to a CTC2B is on hold? ;-)

As to your question, yes, I replaced selenium with silicon in my operational CTC2 chassis, w/o a compensating resistance added, since in NJ where I lived at the time the line rarely went over 115 and was usually much lower (115 is the AC input spec for the CTC2). That chassis is now/still at ETF driving the rebuilt 15GP22 demo there, and since the line at ETF was nicely above 115, I added a 50-ft. extension to the power cord, which conveniently drops the line to around 115.

Pete

But in the event you're not................I'll ramble on. My sacred FBT died of old age. It developed a short in the primary winding very near the core. I could see a tiny blue arc and a whiff of white smoke on the side of the winding near the core when I tried to restart the TV.

I did not cause this tragic failure, I wasn't even in the same room and the HV cage was locked. This FBT was toast, all dried out and brittle. It was non-repairable in my estimation. It had to be replaced.

Am I understanding correctly that u used your apparent vast knowledge to experiment with a virtually priceless object that being the flyback?

The Mona Lisa is a "Priceless object" a Flyback is just a TV part.

Someone simply asked for help, lets keep the rude replies in check shall we?

I know this is a long shot, but, how about rewinding? Has anyone ever successfully rewound a fly or had it done by a transformer company?

I have read about vert out transformers being rewound and I know they are much less complex, much like a power transformer.

---

Some of you need to take a deep breath and chill out. It's just a damn piece of equipment. Tomcomm's set may have ran at that current for 50+ years with no problem. But folks, it is a 55 year old transformer, and sorry, but sh*t is bound to happen. No one engineered these parts to operate a half century into the future. Furthermore, it's his set and his money and the idea of denying him the right to buy a replacement part (or do penance for that matter) is childish and ludicrous.

Correct me if i am wrong is your CTC2B the same as the CTC2 in the CT 100 that uses a 6CD6? if so according to the RCA receiving tube maual RC-21 "the average cathode current............... 200 max ma" . Whats up with 3R264?

The CTC-2B uses a 6CB5 which is spec'd for a design center maximum cathode current of 220 ma. Having said that, count me among those who aren't particularly sympathetic...or surprised.

denying him the right to buy a replacement part is childish and ludicrous.


The idea that anyone here could deny anyone else on this forum anything is what's ludicrous, taking someone's OPINION for fact is also childish...


That said, it is my OPINION that this thing burned up because of the 'mods' that were done to it. Maybe it's just me, but when I read things like:

'I intend to start reducing the CRT Ultor HV from its present 34KV....'

and

'I jacked up the +400v B++ supply to above +420v'


I get a certain 'cringe factor', know what I mean? Not only was the 21AXP22 never rated for that votlage, but I severely doubt the flyback liked being driven that hard. How many times do we see people get warned again and again about HOT current, recapping, variac starts and the like? Seems obvious to me that the experimentation took it's toll, that's all I'm saying. I do hope the set can be fixed, but as I said I don't think you're likely to find an NOS one.

Some of you collectors are certainly a strange breed...

The burden is on us,the keepers, the possessors. We must be good stewards of the rare and dimminishing.For every one good thing we do to preserve something there is at least five things we can do to destroy it.
No amount of chastisement from others could ever reach the level punishment that i would inflict on myself for hurting precious treasures.

The idea that anyone here could deny anyone else on this forum anything is what's ludicrous, taking someone's OPINION for fact is also childish...

You know, what the guy needs is constructive criticism and advice such as the replies from andy and kx250rider. Suggesting he doesn't "deserve" another flyback is asinine. Period.

No amount of chastisement from others could ever reach the level punishment that i would inflict on myself for hurting precious treasures.

Three days ago I watched someone drive a pick axe into the side of an NOS Sylvania color combo with a dead CRT. Guess I should have thrown myself between them. :sigh: Hate to tell you, but not long after we draw our last breath most of our "precious treasures" will probably be scrapped for copper.

Not until they pry them from my cold dead fingers and of those who will continue after.

I know this is a long shot, but, how about rewinding? Has anyone ever successfully rewound a fly or had it done by a transformer company?

Hi,

some years ago, I visited Marcel van Grinsven in s'Hertogenbosch. He had manually rewound the primary coil of a burned flyback for a 90° Delta shadowmask color tv set. The rewound flyback looks lousy, but it worked! I saw the set working with this flyback.

Meanwhile, he could replace the rewound flyback with a spare one.

I learned that rewinding a primary coil seems not as difficult as it looks like. The reclacing of the EHT coil with a coil from an other flyback model is much easier since the technical values are more similar. I have even replaced a Sojvet EHT coil for a coplor flyback with a ten-years older German EHT coil of a quite different color tv set.

Kind regards,
Eckhard

You know, what the guy needs is constructive criticism and advice such as the replies from andy and kx250rider. Suggesting he doesn't "deserve" another flyback is asinine.


This is the last thing I will say on this, since I already clarified what I wrote:

I NEVER SAID ANYONE DID OR DID NOT 'DESERVE' (your words) ANYTHING. Stop putting words in my mouth, or meaning to my posts that does not exist. If you want to get butthurt about something I've posted, send me a PM. I don't sugar coat reality, I call it like I see it. My first post was my initial reaction to reading OP's post. My second reaction is: I'm not surprised it blew up. You're free (as I am) to give whatever advice you wish, if you have some issue with me personally contact me, and if that doesn't work, a mod.


Has he considered getting professional help with his obvious anger management problem?


I kill terrorists for a living, what's your release?

Hi,

some years ago, I visited Marcel van Grinsven in s'Hertogenbosch. He had manually rewound the primary coil of a burned flyback for a 90° Delta shadowmask color tv set. The rewound flyback looks lousy, but it worked! I saw the set working with this flyback.

Meanwhile, he could replace the rewound flyback with a spare one.

I learned that rewinding a primary coil seems not as difficult as it looks like. The reclacing of the EHT coil with a coil from an other flyback model is much easier since the technical values are more similar. I have even replaced a Sojvet EHT coil for a coplor flyback with a ten-years older German EHT coil of a quite different color tv set.

Kind regards,
Eckhard

I would like to second this idea - if the primary winding is separable from the secondary. The primary winding depends mainly on its inductance for proper operation, since the distributed capacitance is not that large, plus, it is essentially in parallel with the yoke inductance. The secondary (HV) winding is tuned by its distributed capacitance, which means you need the same materials as well as the same winding configuration to get the original result in rewinding the secondary. Using an existing good secondary coil in case that has failed also makes sense, since you will get both the designed inductance and distributed capacitance.

I wish the OP good luck, but also want to say that I personally never would raise the B+ , HO current or HV to improve the picture. HO and HV stages are just designed too close to nominal to do that IMO.

This may be a dumb question but I'm curious.
Have you tried removing the high voltage winding (physically) and running the set without the winding to see if the current rises after a few minutes? On most failed flybacks I have encountered, the secondary breaks down and burns up. This could leave the primary and the pulse windings intact (could I say).
If this is the case, trying just the high voltage winding from another flyback may be the cure.
I "hot rodded" a Magnavox solid state years ago with great results. It died from a shorted (AC hot to chassis) FM tuner which I temporarily connected into the system (stereo and TV all together) and fried the TV and preamplifier.
My two cents.....
I am sorry to hear of the flybacks demise.

I've had success with bad flybacks by doing the following. Remove the high voltage winding, leaving only the primary windings. Fire up the set. If everything appears to work (other than no HV, of course), get a solid state HV tripler of the type used in later color sets. Connect it to the Hor. Output plate and the chassis to produce the HV.

Might not work on your set, but it is an easy and cheap fix if it does, until you can find a replacement flyback (or talk John Folsom into winding one for you!)

The Mona Lisa is a "Priceless object" a Flyback is just a TV part.

Someone simply asked for help, lets keep the rude replies in check shall we?

Yes. I've been a member here for a few years, and I don't remember any case like this where other members "ganged up" on another. Not shame on Tom; but shame on the shamers.

There are at least two AKers in this thread, who are lucky Eric and the other mods are tolerant, and lucky that I'm not a moderator here.

Charles

Unfortunately, Tom's flyback suffered a catastrophic internal short in the primary winding. The heat generated actually caused the HV winding to slump. But there is still some hope. His flyback is in a box beside my workbench. It has been partly unwound, and the winding "recipe" recorded. I have not yet unwound the HV winding. This flyback is a bifilar wound type, with most of the primary and secondary windings wound with two wires in parallel. This makes it that much more difficult to attempt to rewind. The HV winding is a single strand of approx. AWG 38 wire.

I have wound 2 color flybacks so far, one for a 15" Motorola color set, and one for a CT100. The Motorola flyback works, but it has lower impedances than the original, and has a big "dip" in the top of the flyback pulse, which is causing some issues with the gated circuits. So just having the winding turns count recipe is not all there is. More experimentation will be required to attempt to determine what parameters need to change. As for the CT100 flyback, it too measures lower in inductance than the original, and if failed almost immediately upon installation in the set. Unwinding it did not reveal an obvious defect. I suspect wire handling is a critical issue.

I have taken a break from coil winding attempts for the last couple of months, it is just too darn hot out in the garage to slave over a hot winding machine. And other project have managed to get on the bench ahead of the coil winding. But in the next month or so I will get back to it, and see if I can make more forward progress.


Here is a photo of the winding machine, a George Stevens model 225-AMVP universal progressive coil winding machine, made in 1964. Some of you may have seen this at my ETF presentation on coil winding.

I will report progress as it is made.

I intend to start reducing the CRT Ultor HV from its present 34KV....'

and

'I jacked up the +400v B++ supply to above +420v'


I get a certain 'cringe factor', know what I mean? Not only was the 21AXP22 never rated for that votlage, but I severely doubt the flyback liked being driven that hard. How many times do we see people get warned again and again about HOT current, recapping, variac starts and the like? Seems obvious to me that the experimentation took it's toll, that's all I'm saying. I do hope the set can be fixed, but as I said I don't think you're likely to find an NOS one.

..

I have to put my "2 cents" in here too.
I agree that the "turbocharging" is likely what killed the FBT.Going to OVER 420V on the B+?? If it was MY set...and I wanted to put silicons in I would have put some "series resistance" in line with the diodes, say, 50 ohms/10 watts or so. This would have kept the voltage from going over the limit.

And...34 KV?? Man...that is HIGH Voltage!! I have worked for a LONG time on tv's and I have only seen a FEW sets that high, such as a FEW sony prjoo sets, and a couple of 36" CRT's, that were 35KV. Most others are UNDER 34KV. And ALL sets with chassis tubes were under 28KV, to the best of my knowledge!! I would NEVER DARE to run a 21AX at 34KV--I would be afraid that it would kill it, and if not-- some REAL X-rays would no DOUBT be produced--since those tubes did NOT have x-ray protection.

Having said this--your experiment DID produce a BEAUTIFUL picture--like I could not BELIEVE!! No doubt the super--HV and boost had something to do with this.

IN short--I look at it like a turbocharged engine--and an OLD one, at that. Say--putting a 12 PSI boost on an old Chrysler 2.2L--and SURE you WILL get a LOT of power and performance out of it-- probably 250HP--for a SHORT time...but not for LONG--as the old engine(or fly and CRT) will NOT stand it.

Once you get the set working again...I would suggest series resistance with the diodes to get no more than 390 volts, and no MORE than 26KV h.v., and NO MORE than 225 MA Cathode current.

As for the "discourse" I agree some of it was a bit "heated", but as it was pointed out--CTC-2B sets are RARE--and the "keepers of the flame" do ANYTHING they can to PREVENT them--or parts like FBT"S-from ENDING UP IN FLAMES, and thus--allowed their passion for their collecting hobbies to steer the discussion. Myself, I have a CTC-5, and it is NOT working yet--as I have little time to mess with it, working and all--but it DOES have and a near--perfect, CR-70 tested, CRT--and the fly looks good--and when I DO "get into it" I will NOT "stress things at ALL.

I DO hope you are able to get your set going again though. Best wishes to you.

Jack.

Hi John, welcome to the fray. Glad you revealed your present involvement in getting my CTC2B FBX replaced. Your proposed complete recreation of the failed windings on my original core is a truly heroic undertaking. I’m fortunate to have you participate. Thanks.

Most members of this thread are resigned to the fact that no oem CTC2b FBX will ever be located and even if were, it would probably cost as much as a recent rebuilt 15GP22! This prompted a number of imaginative replacement solutions to be proposed here. Most consisted of combining the low voltage section of my original FBX with the high voltage “donut” from a working, similar RCA or other early color TV FDX , or drive a new HV tripler module from a modern SS TV for ultor . Unfortunately, it’s the original primary and low voltage windings that have failed and are cooked beyond repair. John’s proposed FBX recreation seems like the only solution here……providing it doesn’t cost me as much as a recently rebuilt 15GP22!

Pete D………. to answer your question: In the mean time, I will use the CTC2B chassis only as a hardware test bed and waveform only monitor for my experiments with external Component video inputs. Seems that the three components: Y, Pr,and Pb, are available on three of my DVD players. Y is the luminance with sync that has no 3.58mhz chroma messing it up so it can extend the baseband to 5mhz which equals over 400 lines resolution, where all our roundys cut off at 3.2mhz or 256 lines! I think I can extend my 21CT55's original final three stages of CRT Drivers to possibly 5mhz without chroma interference. It would be great to see the resolution chart wedge with its lines displayed to 400 lines without all the chroma artifacts we see now. Do any of you see a problem?

Holy Cow! What a nice looking coil winding machine. From the photo that looks like a precision engineered piece - something seldom seen in todays disposable marketplace.
I knew an old EE who was also a ham radio operator par excellence - a master radio craftsman - he would wind his own transformers and coils - by hand! I'll bet he would have really enjoyed that winder in his shack.

I think we have to face the fact that at some point every component will fail, will there be any Flybacks that will work when they are 100 years old? It seems doubtful even under ideal conditions.

Ultimately collectors/restorers are going to have to learn to rebuild, repair and even fabricate unobtainable parts.

Some sets are worth the cost of doing so now, others may be in the future.

Interesting to note this coil winder came out of RCA's Lancaster PA CRT plant when it closed some years back. I is quite a fabulous piece of engineering. But even having the machine is only part of the solution. The original flybacks used magnet wire with special servings (coatings), sometimes made of silk, cotton,celanese, nylon or other materials. It is very hard to find any of these wire types these days. I have been able to acquire some "gripeze" magnet wire. This is enamel coated magnet wire with a special very fine abrasive coating, designed to make the wire have a higher coefficient of friction, so the wires will hold together better on the coil as it winds.
Gripeze magnet wire is still made by the Bridgeport Insulated Wire Co. Surplus Sales of Nebraska has some celanese served magnet wire.

If anyone knows of any other sources for any of these other wire types, I would like to know about it. Thanks.

These guys carry bond wire. http://www.wiretron.com/magnet.html

Litz wire probably isn't appropriate, but it comes covered.

Dissolving rosin in alcohol and brushing it on as you wind is supposed to work also.

John

Does that coil winder machine do that zig-zag diamond shaped pattern with the wire when winding the coil? /\/\/\/\/\/\/\ Supposedly that pattern makes for lower stray capacitance. And is nearly impossible to do by hand.

Yep, the universal coil winding machine does the ziz-zag pattern ,and it IS impossible to do by hand. Here is a photo of the gears , cams, and other items used to set up the machine for a particular winding pattern. The gears range from 19 to 120 teeth, and the heart-shaped cams range from .082" to 1.5" (coil width) . The gears and cams used for a setup is dictated by the coil form diameter, the winding width, and the wire gauge.

John, how do you know how many turns between tap, and gauges of wire to use? do you need to take one apart or are there specs to be found.

btw, you going to fawg this weekend?

All I have to add is:

I hope the set will be running again. The picture you provided of it was beautiful.

I love old electronics. I want to keep it all going for as long as I can.

Someone here said that the minute we expire, someone will let it all go for the price of copper. Maybe. In the meantime, its still mine and I am the caretaker.

Best of luck rewinding the flyback, Mr Folsom. That's one beautiful coil winder!

Bruce

I have wound 2 color flybacks so far, one for a 15" Motorola color set, and one for a CT100. The Motorola flyback works, but it has lower impedances than the original, and has a big "dip" in the top of the flyback pulse, which is causing some issues with the gated circuits. So just having the winding turns count recipe is not all there is. More experimentation will be required to attempt to determine what parameters need to change.

I'd like to put in 2 cents worth of speculation here.
1) I have no idea why the primary inductance is less than expected if the turns count and pattern is the same, except maybe the core gap has changed in the process of disassembly/reassembly. Don't know what kind of gap material was used in these units. When I worked on flybacks in the 60's, we used hard paper gap material in the lab. Later, a material containing beads of a specific diameter would be painted on the face of a mating part for production. This was bright yellow stuff you see on some parts.
There is a danger of upping the inductance by decreasing the gap, in that you will decrease the current at which the core saturates (a bad thing) -but if the gap currently is too wide, it is worth trying.
2) The dip in the top of the flyback pulse is because there is too strong a 3rd harmonic resonance in the HV winding.
a) I don't know if these old flybacks were supposed to use 3rd harmonic tuning - it was common practice by the 60s, especially for solid state sets, because the right amount would flatten out the plate/collector pulse and reduce stress on the horizontal output device.
b) I am beating myself on the side of the head, but it's not helping me recall what to do to modify the strength of the 3rd harmonic - probably involves choice of the dielectric material, but since you generally don't have options, changing the HV winding parameters - more turns and less layers or vice versa. However, as I think about it, it seems to me those kinds of modifications would change the frequency of the tuning more than the amplitude. Right now I feel really dumb, 'cause I used to do this for a living, and the one thing I'm sure of is I'm not remembering it straight.
c) just FYI, some later designs used 5th harmonic tuning to flatten the collector pulse even more - approximating a square wave by a combination of fundamental, 3rd, and 5th.

Edit: there is always the possibility that if you get the correct primary inductance, the ratio of 3rd harmonic amplitude will turn out to be correct -- fix the first obvious thing, and it may improve two problems.

Hi everybody!

I'm sorry to hear about this mishap with the flyback transformer, I think it's one of the worst "oh no!" moments.

I don't know the color flybacks, but I rewound some B&W ones without problems, and from what I saw, they are less critical than one may be led to believe. I even rewound a couple that were wave-wound in a more conventional "layer" winding, these still work flawlessly. In my Bush TV22 I rewound both the primary (bad enamel on the magnet wire crumbling away, so I decided to fix it) and the EHT winding (this one was wave wound and covered in tar, but the acid in the tar corroded the copper). As a result the TV works very good, I'm 600-700 volts short on the EHT, unfortunately I ran out of wire while rewinding. Using a test pattern, I cannot detect image distortion or ringing, so I'm really happy with the results!

A question for John Folsom, if I may ask: what kind of substance do you use to keep together the winding when you pi-wind? Now I have a wave winding machine too and experimented with some shellac, it works, but it's quite slow to set.

Thanks

Giulio Maiocco

P.S.: Sorry about my so-so English...

Giulio, thanks for posting this information. Your work looks good - I know handling the fine wire is very difficult. Also, your English seems fine to me.

I wonder if you have an oscilloscope and high-voltage probe, and can check the shape of the flyback pulse?

I'm curious (again)and was looking at the schematic of a TS-905 Motorola regulator. These are shunt regulated high voltage supplies that, in the case of the Motorola, sample boost and that gives the 6BK4 grid bias thru dropping resistors. It seems to me a balancing act between the CRT beam current and the Shunt regulator tube to keep high voltage near constant voltage. Since high voltage was 34 KV, It makes me wonder if the higher than normal RCA HOT current came mainly from too much B+. Having no regulation would lessen the load on the high voltage as the shunt regulator would be biased to cut-off. I read the drive was OK to the tube (waveform voltage) but was the negative voltage on the HOT normal or too low. Higher RF voltage on the output would be expected but this would tend to break down the high voltage winding. The primary failed from what I read but these generally have around 6 to 8 KV RF on them so breakdown is usually rare.
Since the picture was wonderfully linear, I don't think the flyback had any shorted turns until failure.
When running before the failure, was the flyback running hot? I don't have a schematic on the CT2 series but the shunt regulators seem to be similar in the older sets.
Any opinions?

Hi again

To old_tv_nut: I'm happy you liked my work rewinding this FBT, just to let you know how boring it is, it counts 2045 turns of 31awg wire on the primary, and close to 3000 turns, 2960 to be exact, of 36awg wire on the the EHT winding, all done by hand, so not an easy task.

Yes, I do have 2 oscilloscopes, a Tek 545B and a Solartron CD1400, but at the moment I don't have the needed high voltage probe, I should indeed buy one if I can find one at a good price. As soon as I succeed at locating this probe at a fair price, I'll check the flyback waveshape, no problem!

Cheers

Giulio

DAveWM, my method is to unwind a flyback and count the turns and measure the wire gauge. And yes, I will be at FAWG.

Giulio, That is beautiful work you have done. I don't know if a layer winding approach could be used for color TV flyback transformers. At some point, I may give that technique a try, but I have many avenues yet to explore with my universal winding machine.

while the coil is winding, the ziz-zag structure is all that is needed to hold the coil together. The tall, thin high voltage secondary winding is also self supporting and stable, but I apply a topcoat of silicone RTV rubber to protect the coil and give it additional mechanical stability.

John Yurkon, I am not sure about the third harmonic tuning. I suspect you are correct, but I have no verification of this. I have a book published by Phillips which goes into great theoretical detail into the design and modeling of the windings on a flyback. And while this is helpful in as general knowledge, it does not really help me to know how to modify my recipe to achieve a particular result. I expect some trial and error is ahead of me.

Good morning

sorry to hijack this thread, if any moderator feels this is too much, please remove or move my reply!

@ John Folsom: I'm far from an expert, but I think that layer winding should not be a problem, maybe some changes are required in the circuit in order to obtain as specified performances.

Also, thank you about the info on the pi winding, and now I think I know what I'm doing wrong, the wire needs slight more tension, as until now the "layers" gives a spongy feel when touched and the width of the winding creeps up.

BTW, please have a look at the 2 files I attached, I think this is interesting

Cheers

Giulio Maiocco

I'd have to go look over the schematic to refresh my memory on what all besides the horizontal sweep and HV is unique to that chassis. But one idea might be to break down the flyback section into separate devices; perhaps a flyback from a newer color set to give the sweep, and a simple solid state high voltage supply for the 2nd anode? It should be much easier to solve this problem for this set, than for a CT-100 with the weird deflection angle and integral convergence HV feed, etc.

Charles

Giulio, thanks for those great articles. I will have to go to school with them.

I agree with Charles, it should be possible to substitute in a flyback from a later vintage set, say a CTC10 or so. It would tack some exprimenting, but I think it could bedone.

---

Andy, I know at some point, flyback designs used the layer winding approach. But all the flybacks I have seen up through the 1950 and early 60s were universal wound. When did they switch over? Did this coincide with the use of transistors?

You can measure the dimensions of a flyback with a time domain reflectometer (TDR), a precision digital ohmmeter, an LCR meter, and a micrometer.
The inductance of a newly rewound flyback will probably be different than the original.
You should change the inductance of your new flyback by adjusting the core gap rather than adding or deleting turns to the coil.
Remember, the inductance is inversely proportional to the gap.

---

Dunno if this adds anything to the discussion, but here's RCA's patent covering early Color Flybacks.

Cheers,

Findm-Keepm, not sure if I can use this idea to modify the recipe in the flybacks I am attempting to wind, but thanks for the interesting patent.

---

Findm-Keepm, not sure if I can use this idea to modify the recipe in the flybacks I am attempting to wind, but thanks for the interesting patent.

Sanyo gives the step-by-step in their patent, albeit for a Solid State sweep circuit. Good info on the materials too.


I could spend weeks looking at patents - lots of cool info.

Cheers,

IIRC, all the flybacks I worked on at Motorola in the late 60s had layer-wound donuts (probably bi-filar) with Nomex paper, and potted in a fire-retardant-containing polyester compound, with a silicone outer "tire". The compound was a balancing act, since more fire retardant was better for flame resistance, but increased the lossiness of the stray capacitance, and therefore changed the tuning and caused more heating in the coil.

At Zenith, they developed a combination of silicone oils that duplicated the electrical characteristics of the potting compound, and therefore there could be a quick turn-around of trial designs, since they didn't have to be sent through the potting process; and furthermore, windings could be changed as desired without throwing away a bunch of cut-and-try prototypes. The engineer's bench looked like a horror movie, except that a flyback would be in the big jar instead of a human brain.

Frankenflyback!

Well now that the heat of this thread has subsided and a lot of good FBX info conveyed, I wanted to repeat portions of my initial post that described where I was coming from with my chassis-only 21CT55. Why I feel no guilt regarding my methodology in pursuit of realizing this ancient set’s picture-quality potential.

.................I decided in October 2007 to reactivate the beast after 40 years in attic storage and use it as a test bed to determine and demonstrate in photos, the picture quality this 55 year old RCA CTC2B chassis was capable of producing. As such, it was not constrained to replicate the original circuitry in every detail or even operate to the '55 RCA spec. I jacked up the +400v B++ supply to above +420v with silicon diodes and got a horz boost of almost 1KV. I intend to start reducing the CRT Ultor HV from its present 34KV to the 28KV range while doing a full convergence at each reduction level to determine if I loose ANY picture quality.

Note: All screenshots in the Photobucket below were taken at the reduced ultor of 27kv and a B++ of 420v. No abuse here. It has run at these settings from the screenshots of Nov 16, 2008 until the FBX blowup of March 21, 2010. At no time did the FBX coils get above 135 deg or the B++ fuse current above 260ma. I’ve never opened the HOT cathode to measure its current so I don’t know its value. The CRT is a 21FBP22A, the most advanced and possibly most rugged of the latest RCA roundys

Yes, I brutalized this valuable historical item but there are at least five other 21CT55 restorations on this forum alone. I believe I've succeeded in my goal of demonstrating the 21CT55's ability of displaying exceptional picture quality…………………….


That said, I realize the only reasonable chance of resurrecting this CTC2B chassis is thru the knowledge and skill of Vk member John Folsom who remains optimistic that he will produce a replica of RCA’s second color FBX, possibly this year. I am so grateful that he consented to give it a try. Truly this effort rivals the rebuilding of the 15GP22……as far as I’m concerned. Thanks John for your interest and dedication ………Tom

At no time did the FBX coils get above 135 deg or the B++ fuse current above 260ma. I’ve never opened the HOT cathode to measure its current so I don’t know its value. The CRT is a 21FBP22A, the most advanced and possibly most rugged of the latest RCA roundies


See, this is where you loose me.

Let me just preface this by saying that I don't personally care what you do to your set; it's yours, and you're free to do with it as you please. But you can't say the things you just said, while in the same breath claiming 'no abuse here'. Doesn't make any sense. As I said before, I've never encountered a schematic text that instructed techs to do anything with reading current from a fuse holder. If you want to know HOT current, you read it from the HOT cathode. Since you didn't, I can promise you that it was most certainly higher than it ought to have been. Despite your assurances that the coil never got hot (again, no 'specs' as to what is deemed 'safe' as far as temperature is concerned), it's my conclusion that running the set the way you did is what caused the failure.

I won't speculate on how 'rugged' one tube is over another. I can only tell you that the RCA manual I have in front of me has the 21AXP22 CRT operating at a 25kv ultor, maximum designed voltage being 27.5kv (see http://frank.pocnet.net/sheets/137/2/21AXP22.pdf). The 21FBP22 is designed to operate at 20-25kv, and has the same maximum ultor rating. Any time you exceed a manufacture's recommended ratings, you are asking for trouble. That's all I'm going to say about that.


the only reasonable chance of resurrecting this CTC2B chassis is thru the knowledge and skill of Vk member John Folsom who remains optimistic that he will produce a replica of RCA’s second color FBX, possibly this year.

And I hope he succeeds. I can only hope that you learn from this experience, and check HOT cathode current correctly next time. These old parts were never designed to be pushed beyond their original limits, which many will agree were probably being pushed by the factory when operated within design tolerances.

Again, no bad blood. I just hope that you look for improvements in other areas in the future, because pushing the HV high again will likely lead to the same result. Best of luck.

Tom used a word in describing his set - that word was ancient.
That is what this set is/was - ancient.
Regardless of any elevated voltages or current I am convinnced that old age claimed this flyback - 56+ years, billions/trillions of electrons flowing through 38 awg wire - it was bound to happen.
Early television engineers never designed/dreamed of ANY set lasting for decades - even the ludicrously over-built Zenith sets of the late 60's and early 70's were/are disposable items.
Same goes for countless items...cars...wristwatches...refridgerators...NOT HING is designed to last ad infinitum.

RobtWB is exactly right. Even in the day, under warranty, flyback failures were NOT an uncommon thing. It is impossible to know if Toms operation of his 21CT55 chassis at 420VDC B+ and 27KV HV hastened the demise of his flyback. But EVERY time I turn on one of my "" ancient " TVs, I fear for my flyback transformer. I certainly would NOT recommend operating a vintage color TV at the outside design maximum limits as Tom did, but these old flybacks WILL fail, even at nominal operating conditions. Just the way it is.

RobtWB is exactly right. Even in the day, under warranty, flyback failures were NOT an uncommon thing.

Tell me about it, RCA had a big problem with flybacks in the CTC101 set from around 1980. I had such a set, and yes the flyback blew up after a few years. I miss that set, it had a nice picture, with the comb filter.

Tell me about it, RCA had a big problem with flybacks in the CTC101 set from around 1980. I had such a set, and yes the flyback blew up after a few years. I miss that set, it had a nice picture, with the comb filter.

They had a recall & upgrade kit on that chassis. I put in dozens of those in the early 80s. The "IHVT KIT". Great performing chassis!

Charles

How things are (properly) designed depends on the application.
TV sets - should last a long time under moderate (home) conditions, but not cost more than people can afford. Repair or replacement is assumed rather than regular preventive maintenance.
Phone co. central office - designed to last 25 years almost certainly - assumed to be supporting an ongoing revenue stream with minimum maintenance (actually, design for minimum lifetime cost) and minimum failures. Put more money into the parts with expectation of getting it back in ongoing revenue.
High-tech mil gear - designed to extreme limits in some cases to be able to get extreme performance - needs to be ready when needed, but this may be achieved by constant maintenance in addition to basic reliability if necessary - spare no expense (compared to other categories, anyway)
Automotive electronics - toughest combination of performance, life, low maintenance, and controlled cost - auto manufacturers do NOT want any significant warranty returns of a $30,000 product for failure of a small part, and it has to meet these requirements in repeated environmental extremes.

How things are (properly) designed depends on the application.
High-tech mil gear - designed to extreme limits in some cases to be able to get extreme performance - needs to be ready when needed, but this may be achieved by constant maintenance in addition to basic reliability if necessary - spare no expense (compared to other categories, anyway)


How true! This maxim was repeated in my 22 years of Avionics Maintenance:

"Designed to last a lifetime, or until a Aviator misuses it, whichever comes first"

Guess which happened first....

Maxim these days is 'takes a high school education to fix it, college education to break it.'

lol

Automotive electronics - toughest combination of performance, life, low maintenance, and controlled cost - auto manufacturers do NOT want any significant warranty returns of a $30,000 product for failure of a small part, and it has to meet these requirements in repeated environmental extremes.

I wish that they cared about that when they made that 72 Ford Pinto I had back around 1980. Constantly breaking down. :thumbsdn:

---

I ran into a situation repairing a computer power supply that might be relevant. The power supply had the usual load of bad caps, plus an overheated inductor. It was a simple toroidal inductor with 9 turns of heavy gauge wire, so I rewound it with the same gauge wire. Within minutes of testing the power supply, the coil had gone up in smoke and got hot enough to unsolder itself, so I replaced it with a new coil and all was well.

In trying to figure out what happened, I discovered that the ferrite core had become highly conductive (as in less than 1 ohm across). This basically turned the coil into a little inductive heater. I'm not sure whether the ferrite becoming conductive caused the original failure, or if the original failure (caused by bad caps) caused the core to break down from heat. Either way, it seems like the same thing could happen to a TV flyback core, and would make rewinding impossible. It's definitely something to check.

Toroids used in SWMPs are usually made by winding a strip of a silicon steel alloy. You would measure a low resistance from one side to the other, but since the ends of the strips are open it would not act as a closed loop or turn. Yours may have shorted between one of the layers of the strip and would behave as you described.

I don't know what the core is for the RCA John Folsom is rewinding, but if it's ferrite, MO=Fe2O3 or the ilk, the ferrite has a high electrical resistivity and shouldn't suffer that type of failure.

John

---

I don't think the ferrite cores on these vintage flybacks suffer from any changes in electrical resistance with heat. I believe they were fired like a ceramic, though maybe not at that extreme of temperature. Their only weakness, literally, is their brittleness.

Powdered iron I can believe. It would be pretty strange for ferrite to change that much. Not that strange things don't happen.

However, I was surprised to see the large range of conductivity for various ferrites spanning six orders of magnitude. This table gives the properties and normal uses for ferrites and powdered iron.

http://www.ferroxcube.com/prod/assets/sfmatgra_frnt.pdf

John

Hi Tom , If you were to sell your 21ct55 how much would you ask for it ? I am looking for one of these sets in any condition and am looking to get an idea how much I might have to spend if one comes across my path. Thank's , Dave

Dave..........I assume you know the condition of mine from reading this thread? There is no cabinet so its value is strictly as a laboratory test bed for various "experimentation". Presently I"m using the CTC2B chassis to determine what's involved in making it accept Component 400 line video in addition to its present standard 270 line Composite video. This is the only roundy I have. I have no intention to ever sell it. I would suggest you inquire of VK members Steve Kissihger or Bob Galanter or John Folsom what they paid for theirs or what they think a 21CT55 should go for. Lotsa luck...........Tom

My 21ct55 was a steal at $975. I got very very lucky on this purchase. It had a very dead 21axp22. The crt was the original and was from what we believe was probably the first production run of 21axp22's. They used a 20 pin stem left over from production of the 15gp22's, to mount the electron gun assembly. I had the crt rebuilt at a cost of $500. Later the flyback took a crap and I was lucky that my best buddy John had a spare for me. Cabinette needed to be refinished too.

But based on the rarity of this set, I would probably say it is worth more than a working ct100 with a good crt. But that is only my opinion. I think that CT55's are vastly under appreciated. Everyone wants a ct100, of which there are many more. I think there are only about 8 or so CT55's known to exist.

Steve Kissinger paid more for his. But his was in better condition.

FYI: last year I acquired a 1st generation 21" Sylvania color set. Upon close inspection I discovered that it uses the same flyback as the 21ct55. Both sets were produced at about the same time. And both sets are equally rare.

Thank's Tom , Bob for your replies :thmbsp: I currently have 2 CTC-16 , 1 CTC-16X and a CTC-12 , 2 of which have rebuilt tubes from Scotty and perform quite nicely . I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses. I hope to find a 21CT55 someday and will keep a constant look out for one in hopes to have one as my daily watcher.Thanks again guy's !

Thank's Tom , Bob for your replies :thmbsp: I currently have 2 CTC-16 , 1 CTC-16X and a CTC-12 , 2 of which have rebuilt tubes from Scotty and perform quite nicely . I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses. I hope to find a 21CT55 someday and will keep a constant look out for one in hopes to have one as my daily watcher.Thanks again guy's !

In the meantime, if you find your new 21CT55 leaves you with no room for one of the 16's, let me know ;)

I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses.



FYI, I did some research into black level resto on CTC based sets (I have a 9, a 7 and a 4). I ended up running into an old service document that said black level on those chassis was reset during every blanking period when the blanking tube went into effect. So in theory no resto should be needed, but perhaps the restoration effect of the blanker is not what it should be?

FYI, I did some research into black level resto on CTC based sets (I have a 9, a 7 and a 4). I ended up running into an old service document that said black level on those chassis was reset during every blanking period when the blanking tube went into effect. So in theory no resto should be needed, but perhaps the restoration effect of the blanker is not what it should be?

CTC-4 and later had only partial DC restore in the luma. All chassis had DC restore in the chroma, which is necesary to prevent the color tracking drifting in the opposite direction of the most prominent color in a scene.

In the CT-100, DC restore was done on the individual R,G, and B drives, so both luminance and chroma were DC restored.

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?

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

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.

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.

...

Ultor is adjusted at min of 28kv, max is well over 36kv! HOT cathode reads 128ma.



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).

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?

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

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.

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

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

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".

an occational 40+kv non loaded run with no 6BK4 reg the little 3A2 EHV rect arcs across its full 2in length.


:rolleyes:

And what are you hoping to accomplish by doing that?

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".

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.

:rolleyes:

And what are you hoping to accomplish by doing that?

.

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.

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.


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.

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

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.

For me I wouldn't get obsessed with voltages, currents, et cetera. The picture displayed tells just how close you are.


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.

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.

...

I am now using a 22mf electro across the analog VOM for HOT current measurements. I corrected the posting where I measured 128ma using a DVM. It now reads 180ma at both Hot cathode and at the HV fuse. Seems reasonable since current in is current out in these simple circuits. Ultor / HV reg current only amounts to a 1 or 2ma difference if you want to be nit picking.

Glad to hear I was right.

glad to hear that tom got his set performing properly.thats what we are glad about

My pet peeve is misinformation, sorry if that anoys some of you.

i am sure the "misinformation"wasnt purposely intended to peeve you.i find tom s posts very informative,well written and enlightening.no competition here in this forum.some of us are still learning,others teach and then there is the one who knows everything.i am still learning and glad to associate with these fine fellows.
i personally dont have a pet peeve.just realize everybody has different looks,tastes,actions,etc.can you imagine a forum where everybody was the same?how would you like to talk with people just like you?it would get boring very quickly.as a matter of fact,i am bored with this post.goodnight

http://static.tvguide.com/MediaBin/Content/101018/News/Todays_News_Our_Take/2_tues/101019tom-bosley1.jpg

Don't get mad - get GLAD.

I just made a major capital equipment purchase, a Heathkit HV Probe for $39 including shipping. When used with my 1950 Heathkit VTVM I was finally able to setup my 6BK4 HV reg after I cleaned the 66m resistor with lacquer thinner. It was reading 24m with 50 years of crud on its body. Now the ultor is held at the desired 27KV constant at all brightness levels. Some important readings:
At ac in of 115vac, B++ is 424v, horz system current at fuse is only 172ma (same as HOT cathode), boost is 725v, focus is 5.5kv, Ultor is 27KV. After > 2 hours operation, the FBX primary and HV doughnut were barely "body temp", < 110F!
The last major effort will be the horz dynamic convergence system. The latest pics are with only vert convergence:

GLAD 4 UR SUCCESS:banana::banana::banana:

Those screen shots look pretty good to me.

Dummy question here: What's the reason that HOT circuits typically don't incorporate some type of current regulation circuitry? The way I understand it, is that if you loose Horizontal drive, you end up with a melt down.

Kevin

My attempt at a dummy answer--

Seems to me that the tuning of the HOT / flyback is already delicate enough under good circumstances. Adding another circuit or two for protection in the case of complete horizontal drive failure might have made the whole thing even more unreliable.

How often were there cases of complete horizontal drive failure?

Easy enough to do in the IC age (and they were probably more concerned with keeping HV/x-rays under control than protecting any circuitry)

Maybe I should have stated current limiting instead of regulation. Probably wasn't a threat back in the day when OEM parts were available. But I've heard horror stories of very early paper coupling capacitor failures on mid 50's sets.

Kevin

Those screen shots look pretty good to me.

Dummy question here: What's the reason that HOT circuits typically don't incorporate some type of current regulation circuitry? The way I understand it, is that if you loose Horizontal drive, you end up with a melt down.

Kevin

The simple answer is that anything more sophisticated than a fuse would have been way too expensive with tube technology - the simplest current comparison circuit would require at least one more tube stage. Safety shut downs became affordable with the use of transistors, and eminently affordable with ICs. Even then, there were cases of tolerance issues causing unnecessary shutdowns sometimes. With the wide tolerances on consumer tube circuits, this would have reached intolerable false failure rates.

I suppose if the HOT was self-biased, then it would not provide a large enough current spike as required. Are those running something like a class C TX output?

Kevin

I suppose if the HOT was self-biased, then it would not provide a large enough current spike as required. Are those running something like a class C TX output?

Kevin

The HOT under normal operation is either on hard, so the voltage across it is low when current is flowing; or it is completely off, so the current is zero while the voltage is high. Therefore , the power dissipated is low, because the product of (voltage x current) is low or zero. Without the drive waveform, it can be somewhere in between - this condition of having both current and voltage means that the power dissipated in the HOT goes up drastically.

So, another way to describe the HOT ckt would be like a "switching power supply", I reckon, and class "C" is not too far off.

As we know, in an SMPS, the switch transistors must be on or off, and nOT much in between..or WAY too much current--and then destruction--immediately follows.

So, another way to describe the HOT ckt would be like a "switching power supply", I reckon, and class "C" is not too far off.

As we know, in an SMPS, the switch transistors must be on or off, and nOT much in between..or WAY too much current--and then destruction--immediately follows.

:thmbsp:

oh yea. ive had my fun building DIY SMPS circuits. WEEEEEEE

especially when your not pushing the gates hard enough, you power up your circuit, works for a little bit then... KERRRPLOWWWWWW

weee yea what fun....

Of course a flyback is a type of switching power supply (having designed a couple).

And sweep tubes were commonly used in lower cost amateur SW transmitters, probably running pretty close to Class C (I think you could get 100W PEP SSB out of a 6JE6). You tuned the final to minimum current.

The HOT under normal operation is either on hard, so the voltage across it is low when current is flowing; or it is completely off, so the current is zero while the voltage is high. Therefore , the power dissipated is low, because the product of (voltage x current) is low or zero. Without the drive waveform, it can be somewhere in between - this condition of having both current and voltage means that the power dissipated in the HOT goes up drastically.

I don't see a problem with installing a bypassed cathode resisitor to limit plate current, in the event of drive signal loss. My mid 50's RCA B&W has this. But a lot of TV's don't have it. Were they too cheap to spring for a resistor and cap? What am I missing?

Kevin

Perhaps the added cost was not justified? I read that one resistor was saved in the matrix of the 21CT55, vs the CT-100. You might be surprised the lengths OEMs go to for cost reduction; some of it borders on a safety risk, especially with cars.

The resistor elimination in the 21CT55 matrix from the CT100 design was a patent dodge. RCA did not want to pay royalties on I/Q demodulation. Well, thats the story I heard. RCA was known to do almost anything to avoid paying royalties.

The resistor elimination in the 21CT55 matrix from the CT100 design was a patent dodge. RCA did not want to pay royalties on I/Q demodulation. Well, thats the story I heard. RCA was known to do almost anything to avoid paying royalties.

John. I came to the same conclusion recently. The quadrature transformers for the CTC2 and CTC2B chassis have different part numbers. They would have to be since the demodulation angle is different for R-Y demodulation than it is for I demodulation,

I do not have a CTC2B chassis to test my theory, but one must rule
out the possibility that the CTC2B chassis does not properly decode the color signal transmitted by an NTSC broadcast transmitter. The two color signals, I and Q, that are trasnmitted by NTSC standards are in quadrature. In the CTC2B the decoded chroma, Q and R-Y, are not. When a quadrature signal is encoded, it must be deconded in quadrature if crosstalk is to be minimized.

If I am right, the CTC2B chassis is inferior to the CTC2 chassis when decoding an NTSC broadcast.

Now, it is always possible that some stone has been left unturned by me. Perhaps eliminating the one insignificant-in-cost resistor in the CTC2B matrix somehow negates the not-in-quadrature problem. I don't know.

BTW: I believe it was probably Philco that RCA was dodging.

Pete

Here are preliminary comparisons of the original FBX vs the replacement FBX installed in my 21CT55. The screen is still too wide, must be the original yoke is more sensitive then the newer yokes intended to be driven by the replacement FBX. No, I wont try to find a newer yoke………..Tom

When I had to come up with a flyback for my CBS field sequential color adapter (the original was missing) I had to experiment with various things to get the replacement to work with the yoke. I also had too much width. I added an inductor paralleled by a resistor in series with the yoke. Maybe something similar would work for you:

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

Steve, thanks for your interest in my 21CT55 reactivation. The new FBX is very efficient, delivering 32kv maximum ultor and 800v boost with B++ of 398v. Fuse current is same as HOT cathode and runs at only 174ma. B++ is limited with power resistors in the power xformer hv secondary so I can select three B++ voltages with 115vac input from my Variac: Low is 374v @ 160ma HOT, Med is 395v @ 170ma HOT, High is 420v @ 182ma HOT. After running for 3 hours at Med, FBX is bearly warm at B++ of 395v. Excessive screen width is the only major problem. All RCA's CTC7 and above have no width control. They must rely on tight spec'd parts in the Horz/EHV system to give just the right over-scan.
Your experience with using inductors to load the FBX and bleed-off drive to the yoke is consistent with my Fink '57 TV engineering handbook descriptions of width controls . Most of them were shunt where yours is series dropping. I intend to try various schemes to pull mine in.
The preliminary pics I posted above were somewhat disappointing to me. I definitely have chroma leakage in the Q channel since I don't have the proper output filter values installed. Also my camera was on AUTO and bad focus. Here's some full manual pics. The first pic is a stitch of extreme crop of new vs Sony Pro. Q chroma leakage is obvious:

All RCA's CTC7 and above have no width control. They must rely on tight spec'd parts in the Horz/EHV system to give just the right over-scan.



My 7 and 9 both have a plug on the yoke you can move around to get the desired width, while my 4 has an actual switch.

my 9 has that plug also.these sets produce some of the most pleasing colors.i have it along side of my zenith space command and the 9 s flesh tones are remarkable.my xl100 and the zenith chromacolor with the 25vdmp22 are better,but not that much.love those old rcas!

The first pic is a stitch of extreme crop of new vs Sony Pro. Q chroma leakage is obvious:

What are the other 4 pics? Chroma dots on every other one? - like with and without 3.58 trap in the luma.

Of course a flyback is a type of switching power supply (having designed a couple). And sweep tubes were commonly used in lower cost amateur SW transmitters, probably running pretty close to Class C (I think you could get 100W PEP SSB out of a 6JE6). You tuned the final to minimum current.

By the way this is what the horizontal linearity or efficiency coil is for; to tune
the HOT circuit for minimum current which, at least in my B&W sets is also the best linearity. I imagine it's the same in color sets too?
Cliff

The resistor elimination in the 21CT55 matrix from the CT100 design was a patent dodge. RCA did not want to pay royalties on I/Q demodulation. Well, thats the story I heard. RCA was known to do almost anything to avoid paying royalties.

RCA was the last major mfr. to use intercarrier audio. I guess Sarnoff didn't want to lower himself to paying royalties to Motorola Inc.

Here are some later screen pics of the Ferris Day Off. The stitches are before and after FBX swap. Some are after vs Sony. With the exception of too much width, picture quality re facial color graduation and non-combfiltered fine detail, typical of my 21CT55 aka Frankenstein, has been restored. Following advice of this thread, I purchased at great expense DVD of Wizard of Oz and Blu-ray of Gone with the Wind ($10 and $12 respectively. I am now ready for the Lollipop Color of the original Technicolor. I hope I'm not disappointed………………Tom,

Looking real good Tom! :banana: Look forward to lolipop color screen shots on the old gem. 1938 "Robin Hood" is another good one for Technicolor, and I use it often with the 4.
Kevin

It's alive, Its alive! Tom you should change the title of this thread. Your 21-CT-55 is most certainly resuscitated.

-Steve D.

Please pardon my language but that thing looks goddamn awesome! You really should change the name of the thread! That chick sitting on the bricks drinkin' coffee looks hot! (that's my type:D) The detail on the CTC 2B has much better detail too! It puts the Sony to shame!! Oh yeah, did I mention that chick's hot:smsex:

My "Frankenstein" 21CT55 is now off life support and performs as good as original. The screen width is still too wide and has some video foldover that has to be tracked down and fixed. Also the chroma section is showing some color drift near the bottom of the screen occasionally. With 115vac mains, I am running B++ at 396v, boost at 790v, ultor at 27kv. Horiz system current measures 170ma at the fuse, therefore the HOT cathode is the same or less. Please lets not rehash this issue, OK!
I've been playing the "Wizard of Oz" DVD. Am very impressed with the near saturated (Lolly-Pop) screen colors. The screen looks much better than my digital cameras can capture. Seems the CTC2B video system and the 21FBP22A crt have greater brightness dynamic range then the camera's. If I run the camera's brightness down to get good pure whites (tablecloth, blouses etc) without blooming, I loose all low level dark detail in the shadows. The CRT has no problems with these scenes. I find this very disturbing and wish some VK members would drop by for direct viewing.
Anyway, this ".....death" thread is no longer relevant and I intend to go back to my original "RCA 21CT55 #8802897 is Alive!" thread. I feel good about this...........Tom

The limited dynamic range is something that plagues most digital cameras. I have done several exposures of the same scene, overexposing for shadow detail in one, underexposing for highlights in the other, and so on, and piecing the results together in photoshop. This happens a lot when trying to scan in old slides as well, particularly Kodachrome.

My camera is an old 4mpix Canon S40, Judy's is a newer 7mpix Olympus SP-550UZ. They both have dynamic range considerably less than the 21CT55/21FBP22A screen display. I wouldn't want to resort to the heroics of Photo-shop enhancement to demonstrate this ancient CTV. Maybe it's a insurmountable problem. I shoot with ISO of 200 and 1/30 sec. usually F5.6.
The resolution is set for 1024 X 768 native so I don't have to scale it down for posting. Morie is not a big problem. Any suggestions..............Tom

Part of the problem is that cameras (digital or film) that produce pleasing pictures of natural scenes have a contrast boost in the mid tones, with a gradual S-curve compression of highlights and lowlights,compared to the original scene. TV systems have this contrast boost as well. The result when photographing the screen is a double contrast boost. The raw capture of a digital camera actually has enough dynamic range, so if you can capture in raw mode and reduce the contrast in Photoshop, you may get decent results.

There is one other problem that can occur (less so on color CRTs than monochrome) - if the CRT is resolving scanning lines with dark spaces in between, this means that the average level in an area (which the eye can see quite well) is made up of bright lines and dark spaces. Both film and digital cameras have a hard time accomodating that dynamic range. The actual video variation of the bright lines ends up compressed into the highlight region of the digital sensor or film when the average is correct. For best gray scale, the focus (either CRT or camera) needs to be just not so sharp that lines with spaces are visible. Some film recording systems used a vertical spot wobble at a high frequency to just make the bright lines touch each other. Your use of reduced resolution may help by averaging nearby pixels, but it may not be a cure if some of those pixels are overexposed and some are seeing black. An alternative is to underexpose the average, then blur the lines together precisely in Photoshop (by reducing resolution), and then boost the average back to normal. This problem is similar to taking pictures of stars at night. The system really can't handle the dynamic range, but a tiny bit of defocussing changes the brightness modulation somewhat into an area modulation (brighter stars light up bigger blobs of pixels) and gives the right final impression.

So, something to try:
Shoot at highest resolution, with exposure compensated down by at least one stop;
Then reduce the resolution to average the bright and dark adjacent pixels;
Finally, increase the levels to the correct average.

Tom,

This is absolutely astounding!!! It goes to show that there are people here on VK that have a level of technical expertise that goes above and beyone anything that many of us "re-cap and refinish" restorers like myself, could possibly ever approach.

You have accomplished something that only very few on this forum could have even attempted.

Congratulations, you have my sincere admiration and respect for what you have accomplished!

My screen shots are good, but when I view the actual screens of the 21CT55 and my comb-filtered Sonys I realize my two cameras don't do them justice. Leadike and Wayne have offered possible solutions to increase brightness dynamic range of the shots, Since I don't have Photoshop I've decided to try Wayne's suggestion of processing RAW format on both cameras. This seems daunting but worth the effort. As for Bob's reply, I am most humble. I consider him the primer restorer, both in cabinetry, electronics and CRT rebuild technology. All his projects are museum pieces, including his recent 21CT55, which gives me brief pangs of guilt for what I did to mine in '64. I'll attempt to make it up with some outstanding, RAW based screen shots from my " vertical chassis table model" 21CT55 conversion....Tom

A cheaper software alternative to Photoshop is the freeware Gimp, which has a lot of pro features. Gimp works very well, it's main flaw (to me, anyway) is that the workflow is a bit clunky. That could be me just being too stuck in my ways with Photoshop, though.

Always wondered how to get BIG pics posted on this forum:


http://pic70.picturetrail.com/VOL1792/11235128/19914223/322339657.jpg

Well that works but its no bigger than the regular VK forum, only 511 X 400 pixals. maybe thats the max size of Picture Trail's URLs...........Tom. So how did Bob G get his full page??

He probably hosts them off-site.

It depends on how you link. Say that you have a picture stored on some other website. If you paste that URL into your message, you get a link that people can click to view the photo:

http://antiqueradio.org/art/Discovery.gif

If you enclose that URL in tags, the photo shows up here in its native size, which may be big or small:

http://antiqueradio.org/art/Discovery.gif

That's what results when you insert a photo using the Insert Image button at the top of the message editing box.

Displaying a super-giant photo in a message isn't a great idea. People with smaller screen resolution then have to scroll back and forth to read any text in messages on that page. For a very large photo, use the first method and give people a clickable link.

Phil Nelson

Didn't work...........

Tom-BLOWN AWAY by yr work....Good Job !

Phil.....Putting around http://pic70.picturetrail.com:80/VOL1792/11235128/19914223/322339657.jpg
produced same size picture. I'm going to try it next with PhotoBucket.

http://i677.photobucket.com/albums/vv134/tomcomm/55%20RCA%2021CT55%20TV/44.jpg

Phil....The ............. seems to work with Photobucket freebi ok! Its slightly larger than my 1024 X 768
monitor but has positioning sliders to cover entire native pic size. Hey, when I get into posting RAW camera
screenshots this is what its going to be.............Tom

Do you have vid in mod ?
Can someone link to RCA Video In adapter schematic again please ?

that looks great!convergence looks very good and the color is fantastic.beautiful picture and thanks for pic

Newvista...........Here's a tube version of the RCA external input driver for the Roundies I got from Pete D. Hope you can use it..........Tom

Thanks for that diagram, Tom (and Pete). An "Official RCA" video input mod!

Here's the complete article, which I got from John Folsom.

http://antiqueradio.org/art/BROADCAST_NEWS_0656_1.jpg
http://antiqueradio.org/art/BROADCAST_NEWS_0656_2.jpg
http://antiqueradio.org/art/BROADCAST_NEWS_0656_3.jpg
http://antiqueradio.org/art/BROADCAST_NEWS_0656_4.jpg

I built one last year.

Phil Nelson
http://antiqueradio.org/index.html

Newvista...........Here's a tube version of the RCA external input driver for the Roundies I got from Pete D. Hope you can use it..........Tom

Was just thinking your TV must have direct Vid (as well as an amazing CRT)

Thanks to you and others who posted details of this RCA Vid Input, I like the DC restoration & peaking coils.Will try building this one. Meanwhile I adapted another from the net to my CTC-5 that has a tuner problem (details on a separate post)

Since my 21CT55 is not an original RCA restoration but a "laboratory test-bed", I saw no reason to copy RCA's external video input circuitry using early '50s technology. Instead, I implemented a solid-state video op-amp that provides a "perfect" DVD quality 480 line resolution, 75ohm , 5vpp signal into the 55's 1st video amp grid. It also supplies the same 75ohm video at 1vpp to my two comb-filtered Sony monitors and a Leader waveform monitor. Two external video sources can be selected with a toggle switch, each with individual level and offset controls. Presently I run a DVD player with the DVE test disk into one input and a second DVD player with program disks or OTA HD converter into the second input. Now that the 21CT55 's PQ is at least as good as it was before the tragic FBX meltdown I intend to resume my implementation of 480 line component video processing in addition to the present 280 line composite processing, hopefully.......Tom

Thanks for that diagram, Tom (and Pete). An "Official RCA" video input mod!There will be a presentation at the ETF Convention covering both B&W and Color adapters. Wayne Abare describes his solid state adapter for B&W and I my modifications to the RCA 12AT7 circuit. Now all i need to do is write my half.


Pete

Newvista...........Here's a tube version of the RCA external input driver for the Roundies I got from Pete D. Hope you can use it..........Tom

Thanks for this link and also for the Broadcast news links posted by Phil Nelson a few messages later.

I've built a few video adaptors for various color sets but all mine have been using basic transistors.

While they work well, they are certainly not as elegant as one using an IC.

Would you share your IC adaptor schematic with the list?
Regards,
Cliff

I use a Signetics NE5539 video op amp. It drives the 1st video amp grid with at least 3vpp and also the video monitors I use for all PQ comparisons.

http://www.videokarma.org/attachment.php?attachmentid=170198&d=1303143491

You should replace those wax caps!

I use a Signetics NE5539 video op amp. It drives the 1st video amp grid with at least 3vpp and also the video monitors I use for all PQ comparisons.

Thanks very much for the NE 5539 information and schematic. There are instances where as much as 8 volts pp are needed for some sets and also opposite polarity video at that same level, so I'll be breadboarding this to see how far I can push it.
Regards,
Cliff

Hey Tomcomm,

What did you ever do about the Flyback in the 21CT55?

Thanks,
Kirk

Hey Tomcomm,

What did you ever do about the Flyback in the 21CT55?

Thanks,
Kirk

IIRC he cobbled a CTC-20 flyback in and was running that.

His hotrodding antics have slightly rubbed off on me...A while ago I acquired the quadrature transformer from a CT-100 that I want to try swapping into my 21CT55....the CT-100 was an I,Q chroma demodulator set and the CT55 was a R-Y,Q demodulator set... Supposedly the only difference was the quadrature transformer and one resistor in the matrixing... I'd kinda like to see IQ on a 21" screen and it'll be a low risk, reversible sleeper mod.

Tom: The "one resistor" means one less. A couple of values in the matrix are different. I doubt you will be able to see a difference. Only the relative noise in the colors and the (small) spurious color line caused by the different demod axes
will be different.

The difference you will see will be determined almost
entirely by differences between the types of peaking coils used
to replace the nasty white ones that self-corrode. That makes huge differences.
I spent hours and hours getting the right coils to get the sharpest and least ringy color bars. I tried a couple of the ones specified as replacements in the manual, and they were disastrously wrong.

Tom: The "one resistor" means one less. A couple of values in the matrix are different. I doubt you will be able to see a difference. Only the relative noise in the colors and the (small) spurious color line caused by the different demod axes
will be different.

The difference you will see will be determined almost
entirely by differences between the types of peaking coils used
to replace the nasty white ones that self-corrode. That makes huge differences.
I spent hours and hours getting the right coils to get the sharpest and least ringy color bars. I tried a couple of the ones specified as replacements in the manual, and they were disastrously wrong.

In my CT100, I rewound almost all of the peaking coils. It was surprisingly easy. And the frequency responses the exercise yielded resulted in an excellent ringing free picture.

Tom: The "one resistor" means one less. A couple of values in the matrix are different. I doubt you will be able to see a difference. Only the relative noise in the colors and the (small) spurious color line caused by the different demod axes
will be different.

The difference you will see will be determined almost
entirely by differences between the types of peaking coils used
to replace the nasty white ones that self-corrode. That makes huge differences.
I spent hours and hours getting the right coils to get the sharpest and least ringy color bars. I tried a couple of the ones specified as replacements in the manual, and they were disastrously wrong.

I just use the peaking coils off digikey that Nick Miniman82 recommended many years ago. Such as this (this is one of several from that list): https://www.digikey.com/en/products/detail/bourns-inc/9250a-223-rc/969835

I've heard those coils criticized by more than one person, but the people doing the criticism don't site modern off the shelf parts as being part of their better solution...I don't have time to hunt out of production borderline unobtainium, I also don't have the equipment or skills to rewind much less wind new multi-layer coils or properly characterize them or verify performance outside of eyeballing the screen (I also don't have money or time to pick that up)...So until someone comes up with a better list of current production off the shelf parts I can buy off mouser or digikey I'm going to stick with what I know works decently in both of my sets and very soon a set I'm restoring for a customer.

I just use the peaking coils off digikey that Nick Miniman82 recommended many years ago. Such as this (this is one of several from that list): https://www.digikey.com/en/products/detail/bourns-inc/9250a-223-rc/969835
.

Those or the API Delavan (Spelling?) look-alikes were what I ended up with
in all cases. Only one, the 6.8 mH one in the Q, needed a value much different than the spec. I also found them to be the best ones in my HF radio 7 to 11 pole bandpass filters.

Those or the API Delavan (Spelling?) look-alikes were what I ended up with
in all cases. Only one, the 6.8 mH one in the Q, needed a value much different than the spec. I also found them to be the best ones in my HF radio 7 to 11 pole bandpass filters.

Interesting. Is there any significant difference between the API made ones that makes them better in some circuits or is it the same either way? Do you remember what value or part you used for the 6.8mH Q coil?

I just use the peaking coils off digikey that Nick Miniman82 recommended many years ago. Such as this (this is one of several from that list): https://www.digikey.com/en/products/detail/bourns-inc/9250a-223-rc/969835

I've heard those coils criticized by more than one person, but the people doing the criticism don't site modern off the shelf parts as being part of their better solution...I don't have time to hunt out of production borderline unobtainium, I also don't have the equipment or skills to rewind much less wind new multi-layer coils or properly characterize them or verify performance outside of eyeballing the screen (I also don't have money or time to pick that up)...So until someone comes up with a better list of current production off the shelf parts I can buy off mouser or digikey I'm going to stick with what I know works decently in both of my sets and very soon a set I'm restoring for a customer.

Just to let you know how I wound my peaking coils, I used a 1megohm 1watt resistor to wind the coil on. Cut out with scissors two cardboard disc from old business cards and slipped them over the resistor to hold the windings in place. Roughly calculated the number of turns to achieve needed inductance from an on line calculator (I Googled). Bought off Amazon appropriate gauge wire small spool. Made a spool holder from a coat hanger wire C clamped to a table. Fit the end of the resistor I was using to wind the coil in my variable speed power drill. Slowly (5 turns a second) ran the drill. (There was typically around 600 turns for a 1 mH peaking coils so winding that did not take too long).

When wound, I would apply the nail lacquer I bought at Walmart to hold the windings in place. I would then take the coil and measure the inductance using a series resistor, signal generator and oscilloscope to determine the 0.707 point when the inductive reactance equals the resistance. I would tend to be a bit generous with overwinding so that I could remove turns to hit my target inductance.

I did this for almost all of the 8 or so open peaking coils in my CT100. The coils in the I and Q chroma path were fairly critical in order to get a nice flat 1MHz response for the I channel and 500kHz for the Q channel. I frequency swept the luminance and chrominance channels and they matched closely the RCA published curves. And the net result was a an extremely nice sharp picture, free from ringing.

Looking at my bunch wound coils, it would be difficult to distinguish from a new commercial replacement. And my coils looked a heck of a lot better than the original ugly white blobs.

I have used the Digi Key replacements for the failed white coils- the only difference is that I put them in Series to add up to the desired value using a L-C-R meter. I believe it is the difference in DC resistance that causes the ringing- not the coil itself. By increasing the DC resistance it minimized the undesirable ringing (you can see it on the scope) to be indistinguishable.

Great job winding your own!

Kirk

I have used the Digi Key replacements for the failed white coils- the only difference is that I put them in Series to add up to the desired value using a L-C-R meter. I believe it is the difference in DC resistance that causes the ringing- not the coil itself. By increasing the DC resistance it minimized the undesirable ringing (you can see it on the scope) to be indistinguishable.

Great job winding your own!

Kirk

Did you add series resistors or get a large assortment of coils and test them in series with each other until DC resistance and inductance matched target values?

I think I used 3.9 mH for 6.8. I did buy an assortment ane tested each one for inductance using one of those yellow meters anf for self-resonance using a frequency synthesizer, a 1 megohm scope probe, feeding the signal in through a 1 pF capacitor. I used my 5-spice simulator in the actual circuit and tried the best two
in the actual set, sweeping them (with the horizontal system fully disabled as the yoke was not connected.) I used the best looking sweeps. All looked fine when tried on actual pictures except the Q one. That one I tried by mounting the chassis behind the set and trying coils and different values oif the nominally 27 pF cap from the Q demod to ground. It a compormise between the best looking Q channel response and the problem that the best response looks terrible because its much too early ... it would need less delay in the Y delay line and the I filter, which has intentional delay in it . I have actual photos of the restult on +-I and +-Q bars posted on an earlier thread here. I will repost here. Note that the time error is obvious here ... but not on program material. Note that there is an orange bar from crosstalk on green to violet but the corresponding bar on green to violet looks more like luminance. Except for the black and white bars, Y is constant. Note that th I channel looks really good.

The Digi Key coils tended to have a lower DC resistance than the originals- Putting them in series until I had the correct inductance value worked for me.

...It a compormise between the best looking Q channel response and the problem that the best response looks terrible because its much too early ... it would need less delay in the Y delay line and the I filter, which has intentional delay in it . I have actual photos of the restult on +-I and +-Q bars posted on an earlier thread here. I will repost here. Note that the time error is obvious here ... but not on program material. Note that there is an orange bar from crosstalk on green to violet but the corresponding bar on green to violet looks more like luminance. Except for the black and white bars, Y is constant. Note that th I channel looks really good.

If by Q "best response" you mean sharpest transition, then that may correspond to wider than normal Q bandwidth and the early Q timing you have. This will result in some quadrature crosstalk of I into Q, which I think is part of what you see in the yellower left edge of the green in the violet to green transition, and the bluer left edge of the violet in the green to violet transition.

Of course, this could be confused by the presence of a slight ringing in the Q circuit response - if you see a ringing transition, it's hard to separate the Q baseband response from quadrature distortion. To separate things, you need to input a step waveform at the Q demodulator output and see that it's not ringing at the CRT.

Also, there's a question whether the chroma in the test source has wideband I and narrowband Q or is equiband.

I want to modify what I posted above.

To look for quadrature distortion, you can look at the I demodulator output during the Q (green/violet and violet/green) transitions, and vice versa.

If the source has wideband Q, it will cause quadrature distortion in the I demodulator, even in a perfect receiver. This could be a lot of what you are seeing in the transitions between green and violet (but there could also be ringing in the Q signal itself).

NTSC screwed up the Q channel color encoder specs by not including a 920 kHz trap in Q baseband (or a lower sideband trap following the Q modulator), so even with a perfect receiver, it is possible to get quadrature crosstalk from Q into I if the lower Q sideband is not strongly suppressed at the encoder. (The upper Q [and I] sideband is always strongly suppressed by sound traps.)

I reckoned the effort RCA initially went to in the CT100 was to minimize quadrature crosstalk. With the inductances I mad as described, I was able to achieve these response curves which yielded a picture free from ringing yet obtained opptimal chrman resolution.