RCA 21CT55 #8802897 is Dead

[ohohyodafarted]

My 21ct55 was a steal at $975. I got very very lucky on this purchase. It had a very dead 21axp22. The crt was the original and was from what we believe was probably the first production run of 21axp22's. They used a 20 pin stem left over from production of the 15gp22's, to mount the electron gun assembly. I had the crt rebuilt at a cost of $500. Later the flyback took a crap and I was lucky that my best buddy John had a spare for me. Cabinette needed to be refinished too.

But based on the rarity of this set, I would probably say it is worth more than a working ct100 with a good crt. But that is only my opinion. I think that CT55's are vastly under appreciated. Everyone wants a ct100, of which there are many more. I think there are only about 8 or so CT55's known to exist.

Steve Kissinger paid more for his. But his was in better condition.

FYI: last year I acquired a 1st generation 21" Sylvania color set. Upon close inspection I discovered that it uses the same flyback as the 21ct55. Both sets were produced at about the same time. And both sets are equally rare.

[ws407c]

Thank's Tom , Bob for your replies I currently have 2 CTC-16 , 1 CTC-16X and a CTC-12 , 2 of which have rebuilt tubes from Scotty and perform quite nicely . I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses. I hope to find a 21CT55 someday and will keep a constant look out for one in hopes to have one as my daily watcher.Thanks again guy's !

[Robert Grant]

Originally Posted by ws407c

Thank's Tom , Bob for your replies I currently have 2 CTC-16 , 1 CTC-16X and a CTC-12 , 2 of which have rebuilt tubes from Scotty and perform quite nicely . I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses. I hope to find a 21CT55 someday and will keep a constant look out for one in hopes to have one as my daily watcher.Thanks again guy's !

In the meantime, if you find your new 21CT55 leaves you with no room for one of the 16's, let me know

[miniman82]

Originally Posted by ws407c

I wish to do some sort of black level clamp/ dc restore to one of them and am very curious as to how the CT-100/21ct55 performs as to black level responses.

FYI, I did some research into black level resto on CTC based sets (I have a 9, a 7 and a 4). I ended up running into an old service document that said black level on those chassis was reset during every blanking period when the blanking tube went into effect. So in theory no resto should be needed, but perhaps the restoration effect of the blanker is not what it should be?

[old_tv_nut]

Originally Posted by miniman82

FYI, I did some research into black level resto on CTC based sets (I have a 9, a 7 and a 4). I ended up running into an old service document that said black level on those chassis was reset during every blanking period when the blanking tube went into effect. So in theory no resto should be needed, but perhaps the restoration effect of the blanker is not what it should be?

CTC-4 and later had only partial DC restore in the luma. All chassis had DC restore in the chroma, which is necesary to prevent the color tracking drifting in the opposite direction of the most prominent color in a scene.

In the CT-100, DC restore was done on the individual R,G, and B drives, so both luminance and chroma were DC restored.

[Tomcomm]

I have an RCA schematics book that covers all chassis from CTC2 thru CTC20. I zeroed in to each schematic and examined just the circuitry from the HOT thru the FBX to the output that the FBX drives. I was amazed at the lack of similarity of all their horizontal driver circuitry! It was like each year RCA had a contest among its engineers who could make the most circuitry changes from last year! This convinced me that hobbling in a look-a-like FBX from another RCA into my CTC2B was impractical and injurious to my or any other person's mental health. I am even more convinced that John’s approach of replicating the original FBX on his pro coil winder is the only way to go.

However, I will entertain the swapping-in of a different RCA FBX into my CTC2B as a far-out “plan B” backup. Has anyone in this forum performed this swap or knows of any successful swap on a early delta-gun, magnetic converged roundy? Also, are there any RCA CTC4 thru CTC20 FBX available out there, NOS or used, besides the CTC20 at Moyer?

[Tomcomm]

Although my only roundy is a non-functional 21CT55 and I didn't watch the Rose Parade in SD or HD I still feel compelled to comment on this year's Rose Parade screen shots. The OTA screen shots on Bob's thread so far have been mostly taken from premium CTs which conform perfectively with NTSC WB IQ standards. These roundys were undoubtedly driven at their antenna terminals with quality ATSC to NTSC converters. It seems a shame the "pure restoration dictate" precludes chassis modifications which permit direct external composite video inputs at ther first video amp inputs. How many forum members are using ext-video to evaluate their CT's ability to properly demodulate composite video and process it to the CRT without the degradation of marginal RF tuner and limited bandwidth IF amplifiers?

My CTC2B chassis is not constrained by the "restoration" consideration and has never processed the deceased NTSC RF/IF programmed inputs. It has always performed as a pure composite video monitor, driven from DVD, Laser Disk, S-video VCR, C-Band Big-Dish and 4DTV Digicypher. At the time of its flyback meltdown, I was in the process of modifying it to accept Component Video which should extended its baseband luminance and chrominance to a full 5mhz or 400 lines vs the 3.3mhz or 264 lines of NTSC Composite Video. Now if only I can get a replacement flyback that would converge as good as my original CTC2B, I can proceed.
Tom

[kwyant]

John,

I am looking for gears and cams for a George Stevens 225 winding machine, can you help? I noticed a previous post with a picture of a gear and cam assortment. I have the same picture I was wanting to know if you know of any one with any of these gears and cams? I am in the process of trying to purchase some. Let me know if you can help or know of any one with gears and cams to sell.

These are the parts I am currently looking for:

1. Driver Gear - 37
2. Driven Gear - 76
3. Cam - .75
4. Idler - 1
5. A-115-T A series driver gear
6. A-111-T A series driven gear
7. Z-.600 Z series cam
8. 1:1 idler cluster
9. A-691 wire guide arm
10. A-697 nylon wire guide wheel
Thanks, Have a Happy New Year!

Ken Wyant
Current Controls Inc.
353 South Brooklyn Avenue
Wellsville, New York 14895
Phone: 585.593.1544
Facsimile: 585.593.1713
"E" mail: kwyant@currentcontrols.com

[John Folsom]

Ken, email sent. Long and short, I do not have any spare parts. George Stevens Co. still has some gears and cams available, but they are expensive. The gears for the machine are non-standard, so are not available from the usual gear sources.

[Tomcomm]

Just finished installing the new FBX sub-chassis circuitry into the CTC2B chassis. No dynamic conversion, chroma keyer, color killer, chroma blanker pulses from the FDX are connected. Focus out of range, linearity, screens, gray tracking not adjusted.

Power input is 115vac, B++ adjusted for 378v producing 860v boost, Ultor is adjusted at min of 28kv, max is well over 36kv! HOT cathode reads 128ma. The big ultor voltage with a tiny HOT current indicates I need a HOT that matches this new FBX, namely a 6JE6A replacing the original 6CB5? I have to order one and its socket & cap.

The premature screen shots indicate I’ve got a long ways to go on this one to approach this 21CT55's previous posted shots.

[andy]

...

[miniman82]

Originally Posted by Tomcomm

Ultor is adjusted at min of 28kv, max is well over 36kv! HOT cathode reads 128ma.

Read from where, the fuse like last time or an actual current reading from the tube cathode? 6JE6 is a stout tube, heavier duty than the 6CB5 (higher max ratings, anyway). I personally don't believe you're getting 30+kv at that cathode reading, unless you somehow stumbled on a combination that works better than RCA originally came up with.

If you really do want to get a better picture out of this thing by toying with the HV supply, you need to make it 'stiffer'. The electronic equivalent of horsepower vs torque, if you get what I mean. In other words, you need more current and better regulation, not more voltage. To do that you would need a flyback capable of delivering that current, or a pair of smaller ones. Then you would need a way of controlling the extra power, which would mean a pair of shunt regs. Or a better solution: heavy duty flyback, and forego the shunt style reg in favor of a feedback type of thing. Something like an extra winding on the flyback which produces a voltage which can be used to control the drive (like the GE portacolor).

[freakaftr8]

Originally Posted by miniman82

Read from where, the fuse like last time or an actual current reading from the tube cathode? 6JE6 is a stout tube, heavier duty than the 6CB5 (higher max ratings, anyway). I personally don't believe you're getting 30+kv at that cathode reading, unless you somehow stumbled on a combination that works better than RCA originally came up with.

If you really do want to get a better picture out of this thing by toying with the HV supply, you need to make it 'stiffer'. The electronic equivalent of horsepower vs torque, if you get what I mean. In other words, you need more current and better regulation, not more voltage. To do that you would need a flyback capable of delivering that current, or a pair of smaller ones. Then you would need a way of controlling the extra power, which would mean a pair of shunt regs. Or a better solution: heavy duty flyback, and forego the shunt style reg in favor of a feedback type of thing. Something like an extra winding on the flyback which produces a voltage which can be used to control the drive (like the GE portacolor).

This is where I get lost... Usually..

I mean I kinda get it but....
Im stumped.

[miniman82]

What's not to understand?

[Tomcomm]

Andy...Yes, there are two rectifiers: the one closest the FBX is the focus, the other is the EHV ultor. There is no voltage doubler, I removed it.

miniman82...I stated "HOT cathode reads 128ma" This was 128mv across a 1 ohm resistor inserted into the normally grounded HOT cathode.

You stated...."If you really do want to get a better picture out of this thing by toying with the HV supply, you need to make it 'stiffer'. The electronic equivalent of horsepower vs torque, if you get what I mean". Sorry, I don't.

My objective with this "resurrection project" is to get my CT2B operating with the minimum amount of circuit modification, not "toying" around to create the Vintage Color TV Version of Cold-Fusion!

freakafta8....I'm with you!