Flyback core

[Reedvoicer]

I have 2 NOS flybacks for an RCA ctc-25. One of these units has a cracked core, in two places and the other one is perfect. Can these cores be replaced if one is available? Am hoping it's that simple. I'm not a tech but have a great appreciation of tube type color tv's.

[Eric H]

I moved this here so you'll have a better chance of getting some answers.

[Findm-Keepm]

Originally Posted by Reedvoicer

I have 2 NOS flybacks for an RCA ctc-25. One of these units has a cracked core, in two places and the other one is perfect. Can these cores be replaced if one is available? Am hoping it's that simple. I'm not a tech but have a great appreciation of tube type color tv's.

The cores can be replaced, but replacements aren't made. The donut (or 'upper' secondary) is usually what goes bad - if you had a bad flyback in a set, you could use the donut off of your flyback with the cracked core, and swap the original core into it. I did this with a CTC38 flyback not too long ago. Got a NOS 119834 off ebay, only to have it destroyed by the seller's lack of packing. I swapped the donut, lower secondary windings, and filament leads from the new fly to the old core/old frame. Worked perfectly. You have to desolder the ground lead that comes out of the lower secondary from the frame first, then bend the tabs holding the frame to the core, and slide everything apart. Assembly is the reverse of the disassembly.

If you were to sell these, most of the old TV nuts here are adept at replacing flyback cores, so it wouldn't be a show-stopper, just a little extra work in replacing the flyback.

edit: ENSURE you don't lose the little gap spacers - after writing the above, I recall the spacers were gluded to the core end, and had to be peeled off. Some kind of fiber or phenolic gap spacer, but important, for sure.


Cheers,

[ctc17]

I think you sent me a message on youtube about this....? But you used the word conductive and I was trying to figure out what you meant by 'is the core conductive'. Cracked is no problem, in the video where I sub the packard bell flyback into the rca I take the core out of the bad flyback and stick it in the good one. Its just about bending some tabs and exchanging the cores. One has to be very careful and patient.

[Reedvoicer]

Hi. Yes, I did send you a message or two on YouTube about these 2 flybacks. Sorry about my wording of this question. Because one flyback has two cracks in the core I thought it would be a good idea to check the thing with an ohm meter, no doubt a pointless thing to do. It was interesting that the cracked flyback registered zero resistance - leads only a half inch apart. The other flyback registered nothing. This probably means nothing. I have only one "old" tv - an RCA CTC-25. Am told these RCA flybacks live for about ten years. Glad I have 2 nos units. I very much appreciate your videos on Youtube! Thanks for your reply.

[ctc17]

Check and adjust the cathode current and keep the flyback cool. Some people drill holes and use muffin fans, I would bend the cover it points up and leaves the thing open. Just dont sit near it of have it in a dirty/smoky environment. I have a video uploading that shows how to check cathode current.

[bgadow]

Somewhere I have a NOS GE flyback core, so at least some of them were available seperate.

[Findm-Keepm]

Originally Posted by bgadow

Somewhere I have a NOS GE flyback core, so at least some of them were available seperate.

...that's because some GE flybacks were sold as windings only, and service techs sometimes tossed the whole fly, or broke the core - oops, need a core! Flybacks EP77X22 and up were altogether, with core and windings. Previous (below EP77X22, and most ES/ET/EU part numbers) had separate winding/core part numbers. I can't recall the chassis right now, but the last GE chassis to use the core/flyback pair was the one with the 3DS3 "rubber" HV tube. The phenolic gaps were included with both the fly and the core.

GE did a similar process with some early IF/Discriminator coils. RTO-XXX and one other (heck, I forget) series were can/coil separate. If you needed the coil, replace the coil. If you needed the can AND coil, order both. The reasoning was that GE made the coils available to other TV manufacturers in the late 40's/early 50's and already had one part number for the coil, so..... JW Miller had a statement in their coil cross reference book stating that only the coil would be supplied for those GE coils. One of my Wallace Tele-aid schematic books has on it (handwritten) "Order coil only when coil only is needed" or something like that.

Don't get me started on knobs and knob springs.... GE and RCA both offered them separate from some knobs. At the distributor I worked for, we ate the small change and made sure all knobs had one when sold by pairing up the knobs and springs.

Cheers,

[wa2ise]

If the cracks are hairline, and can fit perfectly together, you could try wicking in some superglue into the cracks. Yes, it adds some amount of "airgap", but the existing gaps will be much wider, and it shouldn't be a problem.