Looking for a flyback for a RCA CTC 15
 

I finally found an RCA roundie.
The good:
It looks to be a low hour set most all tubes are still originals.
The PCB's have little to no heat damage.
The cabinet is spotless looks like it is right off the show room floor.
The CRT was replaced in 1968 with a RCA Colorama checks almost NOS with a Sencore CR70.

Now for the Bad:
The flyback is burnt.

So I am looking for a replacement flyback part numbers are:
RCA 113382
Thordarson Fly 277
Triad D304

Any help in finding one would be appreciated.

Thanks
Jim

There were two types of flyback failures in those: a shorted turn which would be evident by a burned stripe around the secondary core and a burn through from the 3A3 cup to the core.

EDIT: Does the 15 have the 3A3 socket???

Back in the old days, we used to carefully scrub down the burned section from the 3A3 cap to the core and put several coats of corona dope on them. We'd do them "in frame" in the house. These would last quite a while, enough time to schedule a flyback replacement or a new TV delivery.

I haven't seen one of these in over 40 years but if it has the burn between the 3A3 and core, I'd try removing the flyback and really cleaning it up well. I'd also use the RTV that doesn't have the acetic acid in it. Might be a permanent fix.

Nothing to lose to try.

John

I think you're confusing the CTC-15 with the CTC-16. The CTC-16 and most later RCAs had the stupid design where the top cap of the HV rect was molded into the flyback tire.
The CTC-15 and earlier all had a wire running 2-3" out of the flyback to the top cap connector of the HV rect. Every RCA color chassis number has a flyback a little different from the others, but the 15 is easy to identify because it didn't use a focus rectifier tube, but instead a a selenium stick focus rect.


How have you checked your original to determine that it's bad? There some faults and methods of checking that can easily fool you into thinking the flyback is shot. I've had it happen to me before.

There was an rca tech note that said you seat the 3A3 into its socket with 1/8 th clearence. Then put the top on, and make sure its bolted down tight. Dumb design.

The focus stick I guess wasn’t ready either - they went back to a tube…

Didn’t Zenith just use a rectifier with a conventional setup? RCA seemed to make things stupid at times…

With it out of the set and on the bench the resistance from the core to the connection for the rectifier plate (3A3) measures about 200 Ohms. one side has a burn from the plate wire.

luckily one of the other members has a NOS RCA he is willing to sell.

Will post pictures when I get it in and hopefully working.

Can the CTC-15 fly be converted for tube instead of the solid state focus?

Probably, but why would you want to?
All you would need to do to use a focus tube is add a focus winding on the flyback frame using 10KV insulation rated wire.
However every heater load on the flyback increases horizontal output cathode current, reduces HV, and increases opperating temperature of the flyback...All of which are bad things to do.

On sets with tube focus I often disconnect the focus tube heater winding, leave the tube in for appearance, and stick a cheap modern 5KV PIV rated diode in. It reduces load, heat, and stress on the flyback and horizontal system, and improves focus in most cases.
I can give you a part number for a cheap modern diode if you want.

not to mention. you will be very hard pressed to find a socket for a 2av2 that wont wanna arc out, not too many original ones out there...

i may have one i will look shortly

sorry i do not have that one i have one for a ctc-20 chassis.

That fly is rare, it only works in a CTC20 chassis! 70 degree deflection.
That RCA distributor didn't even have one in stock and that was years ago!
That set was a dog anyway.

I have a Silvertone, Warwick built chassis that is one of the 15 clones, although the layout is different. I have to look at the F/B to see if it's close. The yoke is made by RCA, but not sure of the F/B. It could be similar, as it uses the same focus rectifier and I'm sure that the H/O circuit is similar.
It's strange that the 15 is the only RCA color chassis that used it and others copied it. :thumbsdn:

I'm guessing RCA went away from the solid state focus rect because the tech wasn't ready yet. Didn't they hold onto the 1V2 or 2AV2 up till the end of the tube era? Oh yeah, the 1X2 in the CTC-2 and 4 :)

If in the instance you only had a ctc15 fly when your ctc16 fly dies, and you want to adapt to the existing circuit, but this idea seems to make sense as well. Part number? I found this on Mouser https://www.mouser.com/ProductDetail...BIClpyBQ%3D%3D which would probably work... Also, I assume you mount the rect somewhere on the fly phenolic?

That's the same diode I use for focus (I've even used 3-5 in series for HV rectifier duty).
The CTC-15 flys (atleast in the clones I own) did have mounting on the phenolic for the focus rect and 66M resistor. On a stock CTC-16 you could probably use the focus rect socket for one or more of the terminals.

I'd study the CTC16 and 15 schematics carefully before putting a 15 fly in a 16. IIRC the horizontal stages, their windings, and the windings for the chroma burst and H AFC circuits are different...you might need to extensively modify multiple circuits for such a swap to fully function.

IIRC all Zenith rectangles with high focus used a stick rect. Later
roundies also I think but it has been a loooong time.
I like sticks myself. No more reliable but easier to fix. Always hated doing
filament winding & sockets on tube jobs.

73 Zeno:smoke:
LFOD !

I transfered the tire from a CTC15 flyback to the frame of a burned CTC16 flyback and kept the original pulse winding assembly. Worked fine, just need to remember the short plate cap lead when lifting the cage cover!

My only experience with a tube Zenith rectangular set was one we got from a friend, that started arcing badly one day. When you're 10 and that happens and you're alone, you don't think much beyond yanking the cord out of the wall...

ISTR peeking in the back and seeing a TALL HV box. Beyond that, I don't know what was in there...

When the HV rect winding arced out, I used to just cut away the winding and use, what they referred to as a "Solid Tube".
I assured the customer that it was less expensive to do it that way. :thmbsp:

Fly 277
 

There one on ebay right now. Wants $235.

How did you get the tire off? Does the core come apart in the middle? I don’t see how you can get the tire off the core

The RCA ones come apart quite easily. Straighten the one tab at the top of the frame above the stamped numbers and pull. Sometimes there are spacers between the 2 core pieces, have to be careful to put them back.

Question on using a new silicon diode for the focus rectifier vs original tube diodes. I like the idea of removing the heater current from the flyback, is there any concern around an increased focus voltage or the change in reverse resistance?

To further "lighten" the load on the flyback is there any reason not to use a silicon diode for the HV rectifier too? Note I understand there is a line to where you should just get a modern TV, but flyback transformers are getting hard to find.

I have also seen they use to make solid state devices that plug into the tube socket but I had thought I read they are prone too fail and it is just better to keep using a tube, not sure if that is because they were selenium, wrong ratings, or just 50+ years old.

You would get a higher voltage output going to a solid state doide, not much but the regulation would be tighter given the lower resistance. 1N4007's, are good for 1Kv each and the focus is about 3 to 5Kv, add another for good measure.
You could do the anode side as well with a long string of 4007's, the only issue is the 1N4000 series of diodes are not exactly fast, the 15.734Khz horizontal might be too high for them and a failure is almost guaranteed to burn up your flyback. Personally I'd stick with the original tubes, my Magnavox T940 runs a 3CN3 for the HV, 480ma heater which comes out to be just over 1.5 watts at 3 volts. It put up with 3 of us kids and never had a flyback issue, its still running with the same HV tube today.

These are good for 5KV. https://www.mouser.com/ProductDetail...BIClpyBQ%3D%3D

I use them all the time for boost and focus in color TV. I've even strung 5+ in series as an HV rectifier substitute.