RCA 21CT55 #8802897 is Dead

[old_tv_nut]

Originally Posted by yagosaga

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.

[Zenith26kc20]

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.

[AUdubon5425]

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.

[miniman82]

Originally Posted by AUdubon5425

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...

[AUdubon5425]

Originally Posted by miniman82

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.

Originally Posted by Red Raster

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. Hate to tell you, but not long after we draw our last breath most of our "precious treasures" will probably be scrapped for copper.

[miniman82]

Originally Posted by AUdubon5425

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?

[Red Raster]

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?

[David Roper]

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.

[Red Raster]

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.

[Red Raster]

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

[Steve McVoy]

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!)

[RobtWB]

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.

[Eric H]

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.

[John Folsom]

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.

[jeyurkon]

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