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  #31  
Old 10-26-2010, 06:02 PM
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Possible FBX Solution

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?
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  #32  
Old 10-26-2010, 06:09 PM
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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.
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  #33  
Old 10-26-2010, 08:12 PM
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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.
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  #34  
Old 10-26-2010, 08:17 PM
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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.
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  #35  
Old 10-26-2010, 08:29 PM
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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
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  #36  
Old 10-26-2010, 10:51 PM
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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.
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  #37  
Old 10-26-2010, 11:30 PM
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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.
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  #38  
Old 10-27-2010, 07:43 AM
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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?
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  #39  
Old 10-27-2010, 08:42 AM
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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
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  #40  
Old 10-27-2010, 09:41 AM
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Quote:
Originally Posted by John Folsom View Post
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.

Last edited by old_tv_nut; 10-27-2010 at 09:44 AM. Reason: another idea
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  #41  
Old 10-27-2010, 09:55 AM
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Giulio Maiocco Giulio Maiocco is offline
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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...
Attached Images
File Type: jpg lopt1.jpg (62.3 KB, 108 views)
File Type: jpg lopt2.jpg (53.7 KB, 84 views)
File Type: jpg rewind1.jpg (130.6 KB, 88 views)
File Type: jpg rewind2.jpg (69.9 KB, 65 views)
File Type: jpg rewind3.jpg (88.8 KB, 86 views)
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  #42  
Old 10-27-2010, 10:01 AM
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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?
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  #43  
Old 10-27-2010, 10:08 AM
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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?
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  #44  
Old 10-27-2010, 10:41 AM
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Giulio Maiocco Giulio Maiocco is offline
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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
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  #45  
Old 10-27-2010, 12:21 PM
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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.
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