RCA Flybacks
 

Simple thread and right to the point.

Will certain RCA flybacks swap chassis to chassis?

Like for example, will a CTC20 Fly work in a CTC16 chassis? They look the same. I know these are becoming rare parts, so I'm wondering if they swap.

I do know that there are some roundie flys that can be subbed the differences are the hardware and the layout of the connections. I don't know if the flys for a 16 and 20 can be swapped but it can be done with modifications, careful mods.

You would have to match circuit voltage and current points. Frequency is the same, tunes
parts would need to be the same, you would probably have to change cap values so
you would still have a tuned circuit for the primaries & secondaries. Voltage taps would
have to be modified so the rest of the attached circuits would work.... Could be some work....

.

Simple answer: Nope. RCA flybacks aren't interchangeable. Even the CTC16 and CTC16X have different flybacks. RCA used the same style flybacks, but the inductance, resistance, and winding count are all different. See Miniman82's thread on RCA flybacks for the cross to Thordarson/Triad, and you'll see the spread.

Even Muntz copies of some RCAs used a different flyback - I researched that before obtaining a spare fly for my CTC16. Sadly, RCA quit making tube flybacks in 1979, and Thordarson and Triad were the only aftermarket makers after that, up until 1985ish, when they quit supplying the common flys (FLY277, 308, 312) for RCA sets. There is a finite quantity left, and finding them is harder now.

Well like squirrel boy said its involved but where the differences are would have to made up in several areas, cap values or resistor values. Of course fly backs are not interchangeable that's why there things to be done in order to use a fly back from one set to another, like maybe but not sure ctc11 and ctc12 . The later 60 s may have been harder or not possible at all to think about swapping flys but the early like the 11 and 12 could very well work with minor mods.

Moyers has the last stash of RCA flybacks, but no CTC16 and earlier flybacks, only CTC17X:

http://www.ebay.com/itm/RCA-115876-T.../321551989338?

I called them right after Christmas, as I had a lead on a CTC15 with a bad flyback, but they let me know that CTC16 (113382 and 115876) and earlier flybacks were all gone...

My Thordarson data shows significant winding differences between the CTC16 and CTC17 flys...

Edit: Moyers is showing one CTC38 flyback, albeit the wrong part number listed 119824 instead of the correct 119834...

Be sure and share those mods when you see them!

I was probably the one to get the last fly 305 from moyers and i wound up trading tv collector the fly for a good 7jp4. The fly305 was for my ctc16 clone in a Maggie. And yes I heard the 16x is different but I never looked into that being I don't have an x series. I have a 16 chassis that now I don't have a spare fly for and if the original goes bad I will get another early fly 70 degree fly and I will post what was done to make it work. I also have a 12 that has a new fly 273 and a 15 with a new fly as well so I won't have to worry about those. The fly273 is probably the hardest to find the others I got from moyers. The 273 I got on eBay from a lot of fly backs and I spotted the box that showed fly273 and asked about getting a pic of that one and the owner asked if I need just that one so I said yes and he took it out of the lot relisted the others and sold me that one for 10.00 . But I'll never find another I'm sure, even for that cheap.

Electronic Surplus has a bunch of Thordarson flybacks, but no RCA stuff left, sadly. eBay and ETF classifieds are where I found my flyback - for my CTC16 and a CTC38 I used to have. I have saved eBay searches for about 19 flybacks by part number, and a generic RCA High-Voltage transformer search saved as well. I haven't run across any valid stuff in a while, although bgadow has a listing that i get results from.

Cheers,

The CTC20 fly was an odd-ball. It was used in the last RCA roundie.
The big RCA distributor in town, didn't have one in stock. I had to wait for it. That was in the early 70's. :sigh:

Yup, it was based on the CTC-19, which was a wholly different chassis (full of 6GH8s) designed to drive the new 19" small-neck rectangular tube, then back-engineered to drive the old Roundie tube.

Looks like at some point someone will have to begin rewinding flybacks from burnt
out ones.... It's gotta be easier than rebuilding a picture tube..... People with good
spares should measure all important parameters like resistance, inductance, and
all that good stuff, wire diameter, and begin keeping records, so when a rewind is
attempted it can be compared to NOS specs.....

.

.

Oh. Well that buggers up the works then. Well at least I have a complete metal CTC20 then.

What usually goes bad is the donut so when they go bad why not just use the solid state hv module there are loads of them on eBay. That unit takes care of the cart voltage as well as the focus voltage, IIRC .

I don't think that is all - the donut is the primary and the secondary, so what generates the HV?

Solid State HV module - care to elaborate?

I know the Thordarson guide I have has resistance specs, maybe windings.

The achilles heel of RCA has always been the flybacks, and i made sure I had a spare lined up for any set I owned, except for a CTC76 XL100 set. As little as I run my CTC16, the only failure has been the focus coil and a seized efficiency coil.

I think what he means is why can't a modern fly back be made to work in antique sets? A solid state high voltage section instead of what the sets have now.

By dough nut I believe he means the outer HV winding. On some sets where the HV winding has been fried (and all else is fine) I've heard of some success being had in disconnecting the HV winding and driving a trippler ('solid state HV module') off the H out tube plate to get HV.

That would be quite a feat of engineering! SS yokes are quite different from tube ones, and the tube sets have things like dynamic convergence, and synch pulse windings that most SS flys lacked.....Making up for those differences and incorporating something like that into the existing circuits would be a challenge even for a team of the best of us.

There are some limits to what you could do here..... For starters, you could probably
only easily adapt tube to tube H output things, first drive coil winding voltage, which
gets you into the ball park for output voltage, same with current. And there are all
those other taps mentioned above. Tube circuit impedance's, don't forget the yoke is
also part of that circuit too.... There is lots to think about here.... Better to rewind a correct
part that has failed, than to try and re-engineer a 1/8 of a tv to fit in a part that may not
last too long when yer done....

.

The hv tripler would make the hv in place of the secondary, donut while yes the primary stayed intact. I think someone here on karma already posted that that very thing was done but don't remember who, it was awhile ago. There has to be a simpler why other then rewinding a primary not to mention a secondary, donut.

You're probably referring to this thread, where a fella in England describes how he replaced a HV winding with a tripler (although in a B&W set).
See post# 18.
http://videokarma.org/showthread.php...winding+flyack

Some translations of terms would probably help:
'Overwind' = HV secondary, 'donut', 'tire'
'EHT' (Extreme High Tension) = HV to CRT anode
'LOPT' (Line Output transformer) = Flyback xfmr.
'Line Output Valve' = Horiz. output tube

Note that he had to add some capacitance to the primary to compensate for the capacitance lost due to the missing 'donut'.

Earlier posts in the thread describe the perils and pitfalls one would encounter trying to actually rewind a flyback.

Well I didn't think there was that much involved seeing as I thought the secondary , donut only made the hv for the crt anode to have the 23 kv for the crt to conduct in the way it was designed for. I also thought the primary was responsible for certain voltages via induction as well as geometry.

It would be nice to have some concrete results - all I'm hearing is "I believe," "I think" and "I've heard"...

A schematic of the mod, a screenshot, and a narrative would be nice.

I have dug out bad HV rectifiers from potted flybacks ('twas nice to have a dentist office next door with an underused Xray machine) and I've seen an doubler added to generate HV in a Conrac color monitor with a bad (internal arcing) potted doubler. That one was in an ATE station aboard the USS Theodore Roosevelt and our NDI shop Chief did the Xraying. We used a doubler originally used in a Xerox machine, after first frying a Tektronix doubler from an oscilloscope - it didn't have the current capability. The arcing caused tearing of the raster, and with text being the primary display, it made it unusable.

To try a tripler in a tube RCA with the usual 6JE6, 6DW4, and 6BK4C would be problematic - coming off the plate of the 6JE6 would provide HV only - no horizontal sweep, and coming off the top end of the primary would add capacitance ( a tripler is all caps and diodes, with a possible resistor if a focus tap is provided) - you might be able to use a doubler in lieu of a HV rectifier if the HV is low, but regulation might cause issues - shunting a doubler would take a bit more current through the 6BK4C, and I dunno what that might do. A donut swap from a good flyback might work, but I've never seen two RCA flybacks with the same donut (PRI/SEC) schematic - I'll post the Thordarson schematics to show what I see...

RCA flybacks, as some have mentioned, provide much more than just HV - they provide Horizontal sweep to the yoke, focus voltage, sync pulses to the Chroma circuits, and convergence signals for the set. True they all operate at 15,750 Hz or so, but inductances, winding counts, and resistances all differ, making it all but impossible to easily swap out.

Seems like Tom Albrecht was experimenting with triplers, in a Philco projection set for one. Seems like he tried one in a color set too, but I can't recall the details.

And it probably worked, lol.....

A little math here guys...

A TRIPLER is NOT going to give enough HV for a color tube from the H-out line. They normally are driven with between 8-10KV, to give out about three times that. BUT the h-out pulse is around 5-6KV I believe...and that will ONLY give at BEST 18 or so KV...NOT NEARLY enough..

Now--a QUADRUPLER--MIGHT work...they get about a 7KV pulse and give out 4 times that or so.. SO driving with 6KV might give 24 or so KV..while likely WOULD be enough...

There are still a few ECG 536A and ECG 550 Quads out there floating around...

It might be a good experiment...but I am NOT sure how well it will work...if at ALL, as others have stated...regulation, geometery and all else might be a real problem...

As promised, here are the RCA Flybacks, from CTC7 to CTC31, minus the CTC12 (Fly273) and the CTC20, a FLY352, the oddest of them all.

Missing the Fly 284 that was for the CTC 9 and late 7?

...

Yeah, I'll add it and the 352. My point was to show how different the flybacks are, and how difficult it would be to adapt one to another chassis. FLY312 and 308 look close, but if you want color, you've got to use the original. I made a mistake and put the wrong fly in once, and it wouldn't even light off. Even after swapping leads (the windings have different pinouts), I could get it to light off, but with a drive line, no color, and no AGC. 'Twas a 34-dollar mistake - had to spend that to get the correct flyback after a weeks wait.

The OP is working a CTC16 with a questionable fly - and no fly except the RCA/TRIAD/Thordarson/Hallordson exact replacement will work. Me? I'd work to prove it wasn't the fly first - by checking cathode current, 6BK4 current, and the drive to the 6JE6, as well as a swap out of the tubes with known good ones. Then, start unloading - focus rectifier, boost diode, and 3A3/cup. Good drive, good 6JE6, good cathode current, and still low HV? Probably the fly, but still plenty to check.....

I was curious how the Fly 283 and 284 compare.

I had good and similar results with a nearly-failed CTC12 flyback.

I wonder if--

Your flybacks, (Line Output Transformers) are suffering a damp-coil condition like some British Bush/RBM B/W sets.

The HV Overwind was a pitch covered/wax impregnated coil in a doughnut shape, and some years of dis-use,--especially with a set stored in a damp barn or basement would allow moisture to creep into the coils via tiny cracks that appeared in the pitch/wax over the years since it was made, causing low EHT (HV) and worse still, falling EHT as the transformer warmed up, to the point the picture would expand and eventually completely disappear and the horiz-out bottle plate glow under the stress.

A period of 'cooking' the HV overwind coil by passing current through it carefully monitoring the heat in the coil to around 100-120 deg C for some hours, (I usually leave 'em overnight at this temp on the 2 or 3 Ive done) cures the issue.

Some guys have had success by storing the complete transformer in/on central-heating system hot-water storage tanks for some months...
--I prefer my method--Much quicker!

--A good coating of the insulating-varnish of your choice then seals it all up keeping the coils dry....

Ancient Rca ctc2b FTB replacement
 

Ancient Rca ctc2b FTB replacement

I've been there, done that from Nov 30, 2010 to Mar 10, 2015. Used an RCA 117426 FBT.
This FBT was used in the CTC16 and CTC20. To me it was a major effort to get it right
in 80 days, elapsed time. The result was a transplant that produced screen shots eqivalent
of my original FTB. That quality is near 1986 Sony SS comb filter quality today.

This exercise is well documented in the included VK "RCA 21ct55 #8802877 is dead" thread.
It is long technicaly and somewhat contentious but good reading.


http://www.videokarma.org/showthread.php?t=249148

Um, the 117426 was used only by the CTC20.

See the whole lineup:
http://www.videokarma.org/showpost.p...79&postcount=9

I'd hate to see someone buy a 117426, only to find it doesn't work.

if you want to try, you can find off brand flybacks (not listed above) that can be subbed. Its not easy but can be done. As an example I transplanted an entire fly tire for a Magnavox to a Sylvania. They were both RCA clones, but the Magnavox mounts the fly on the left side of the chassis (view from rear). It was still a clone circuit wise. The Sylvania was more I direct clone, both of the CTC-15 circuit.

If you review the schematics you can look for circuits that are basicly the same.

Funny thing was before I did the Swap of the Maggie fly I used some odd ball Admiral IIRC tire. The set worked but was just a bit down on horz power (the sides would not quite fill out and the HV had no head room. I tried increasing the screen current but it was really just not enough plate load from the fly. It would work fine if I bumped the line up to about 128vac. the cathode current was about 150ma max so the tire ran stone cold. I even considered just leaving it that way just to not worry about flybacks. I still have that transplanted fly somewhere as a spare for any CTC-15. Oh I think the orig fly was for a 19" Admiral portable.

That's what I like about having the tire schematic - you can match the electrical characteristics, and hope the mechanical will follow. Years ago, I tried a Muntz color flyback tire on a CTC16 with mixed results - I had HV, but the rest of the windings were either out of phase or not quite right, leaving me with no color and poor AGC. The similarities among the early colors to RCAs helps - a Philco, Packard Bell, Olympic or other clone fly might work electrically - I've just never gone that far. I've got 11 RCA tube flybacks, all for different chassis, and just dreading the day I might have to use my spare flyback for my CTC16.

On a side note, Horizontal Efficiency coils, focus coils, and Chroma coils are another area I'm stocking up on spares. Still available, but a finite supply nonetheless....

The more I read, the less and less I want to even tinker with this thing anymore. Maybe I should have stuck with Solid State, hah

21ct55 FTB replacement
 

It seems there is some concern the CTC20 I used was not used in the CTC16 and therefore not interchangeable for swaps. I checked the dc resistance of the ctc20 tire versus the ctc16 tire I have as spares. Well for all concerned, they were identical. Both flys had the same lug arrangement and the same added cores for aux signals. Only the mounting plate holes were different, but who cares! Really, if a failed ctc16 or ctc20 can be saved by drilling s few holes and rearranging some pickoff coils I certainly would go for it.

http://i677.photobucket.com/albums/v...psha0u0hl5.jpg