Restore 21CT55 to schematic or as built?

[Zenith6S321]

Bryan, I'm located in southern MD a couple hours south of DC and Balt.

[old_tv_nut]

Originally Posted by Zenith6S321

I started comparing the convergence chassis wiring against the Sams schematic and find missing/different components. I expect this is due to running production changes.

In a later post you say the flyback was replaced - this may have required changes to the convergence chassis if the replacement flyback's windings are different. So, another vote to stick with what is in the set instead of what's in SAMs.

[Steve McVoy]

Zenith6S321, is this a set we have in our database? Could you send me a PM with your name and information on where the set came from?

Thanks.

[kx250rider]

I agree with Steve K... His experience on the early color sets is about as strong as you can get in 2011. Further, I agree that Sams is probably NOT what I'd use. I have (same as Steve) the RCA factory manuals and supplements. I doubt that your TV has any non-factory authorized changes in it; especially if it's been in your hands since '70x. If it had passed through the hands of other TV collectors, maybe I'd worry there had been switchy-changey of things. I had a 21CT55 that had been heavily modified to accept composite input, and was changed to a glass tube, and had been retrofitted with a solid-state B+ regulator. Needless to say, that became a "parts set".

Charles

[Sandy G]

You lucky Dawg...That is a VERY desirable set ! Can't wait to see "Working" pics of it & its "Glorious Lollipop Color"...(grin)

[Findm-Keepm]

Calvert or St Mary's? I'd love to see a 21CT55 live, in operation!

Cheers,

[stromberg6]

When I did my 4 & 5N, I used Sams, RCA service publications, and also noted every step of the way just what each circuit looked like as wired, and had no problems at all other than what one would expect in a restoration. Low hours set, the 4, with all factory mods. One thing I did do in the 4 was put the chroma amp circuit back to original. I believe it was wired to bypass the automatic color control circuit to allow more gain. I like it the way the engineers designed it, but to each his own.
Kevin

[reeferman]

Zen,
I can send a copy the RCA color tv field service guide should you want it.
Phil

[miniman82]

That's right, Wayne. IMO if the HV cap failed, it was probably due to internal breakdown and arcing all on it's own, but that's also likely what took out the flyback. Looking at the schematics, it appears RCA might have realized their mistake. On the CTC-4, the HV tower incorporates it's own set of resistors between the output of the HV rectifier and the shunt reg/CRT. This way even if the shunt or CRT shorts, the resistors end up sinking all the current so presumably the flyback could live. Same principle as the resistor used on sets that used the 21CYP22 CRT- shorting protection. It's probably possible to mod the 21CT55 to include this type of protection; it would not be original so purists might object, but it's cheap insurance against a failure that would destroy an irreplaceable flyback transformer. Just my 2 cents.

[Zenith6S321]

Yeah, I see what you mean in the CTC4 HV schematics. I will add moving that resistor before the regulator to my todo list. Thanks.

[Zenith6S321]

The 21CT55 RCA information that Steve K sent arrived today. Its much more detailed than the Sams And my convergence chassis wiring matches the RCA schematic, which the Sams did not. Thanks again Steve K for the information!!! Now to start recapping and checking all resistance values, cleaning contacts, cleaning 50+ years of dust, etc.... And then theres the cabinet, which I guess I will save for after the electronics are finished.