21CT55 #2628 restoration
 

I'm finally beginning the restoration of my RCA 21CT55. I had intended to begin it about three years ago after I restored some vintage test equipment. Then I ran across Phil's excellent restoration web site. Then I found the Early Television Foundation site and realized my set was kinda rare. I had always thought it was special, but I had no history of early color TV development to know how few were made and that it was based on the CT100 CTC-2. Then I found Videokarma and learned how much I did NOT know about restoring old TVs. The depth and breadth of the knowledge of the members is a treasure. SteveK sent me a copy of the 21CT55 RCA Service Clinic document that is very helpful. I then decided that instead of starting with the 21CT55, I would warm-up with early B/W sets that I was extremely happy to find were actually available. I studied all of Bob Andersen's YouTube restoration videos and learned a lot. So I hunted, bought, and restored a RCA 721TS, a Dumont RA-103, and a RCA 630TS. I mixed those restorations with a Zenith 6S321 Stars-and-Stripes radio that I have used since the 60's, a 1931 Philco Model 90, 1928 Atwater Kent Model 49, and a 1924 Atwater Kent Model 20 radio. As I learned, I picked up additional test equipment along the way. Here is a picture of my restorations arranged in my living room with my 21CT55 waiting patiently. And a few pictures of the 21CT55. Its time has come. :yes:

Dave

Heh, looks like the HV cap in your blew at some point. Interesting way to make the repair, with them all arranged in a circle like that laced with dope.

Can't wait to see the "Glorious Lollipop Color"....(grin)

I was college kid at the time (1974) and could not afford the right part. It functioned ok, but had a lot of corona, hence the slathered on corona dope. I hope to find a better replacement, but I have not started searching yet.

Dave

The original gray 30KV doorknob on my CT55 also went bad. I found a suitable 40KV doorknob on ebay. Mounting was slightly different, but was easily modified to work like the original. I also see that the discharging assembly that grounds the doorknob has been removed. I installed a low RPM cooling fan on the HV cage to keep the flyback cool.

Here is a link to the restoration pages of my CT55 on my web site.

http://antiquetvguy.com/Web%20Pages/...CA-21CT55.html

Good luck and welcome to the CT55 club!

I bought this set from the service manager at Electronic Specialty Company in Charleston, WV in 1974. My dad worked there as the accountant and I worked there a couple of summers during college. The service manager told my dad that the set was originally purchased by a doctor at West Virginia University through Electronic Specialty Co. They maintained it over the years and when it blew a flyback after the CRT had been replaced the service manager got hold of it when they bought a new set. He replaced the flyback, but had not completed the rewiring. The selenium rectifiers had been replaced with diodes before I got it. I bought it for the $75 from the service manager who had lost interest in the project. I found the 30KV capacitor shorted, so the first thing I did was fix that and a couple bad filter caps. That got the set working but it did not see much use. The CRT is a 21AXP22A dated 1957. My CR-70 shows its got emissions in the good range, so I am hoping I will not see purple in the neck when I get HV to it.

It also has a few of the white peaking coils that Nick found were bad in his, so I expect to be replacing mine.

Dave

Thanks for the link Bob! All advice is very welcome. I have the shorting bar along with others bits and pieces. When I got the set it had a chipped brightness knob, was missing the fine tuning knob, the volume knob, and the channel number insert. Here is a picture of the knobs I have, and another of a new brightness knob, a knob that I think is the correct volume knob, a fine tuning knob that I hope to modify to work, and an original "spare" peaking coil the service manager said I would probably need.

Dave

Bob, thanks for the ebay tip for a capacitor. Would a 2700pF 40KV work ok as a replacement for the 2500pF 30KV?

Dave

I've done some cleaning to the chassis. I used naval jelly (thanks bandersen) for the cleaning and to treat the rusted areas. The chassis "before" picture is above, here are some "after" pictures. Also is a picture of HV capacitors that I will replace with the 40KV 2700pF door knob capacitor to replace the mess. I have not yet figured out how to clean the HV cage, any suggestions? I compared my flyback with the two Bob shows in his restoration page: http://antiquetvguy.com/Web%20Pages/...CA-21CT55.html
I think mine is the same replacement Bob is using.

Dave

Looks like the photo of the fine tuning knob in the picture (if that is what it is) is wrong. That fine tuning knob is probably for a ctc5. You need a fine tuning knob like a CT100 uses. IF has a great big hole in the center (about 1.25" dia)

RE: HV cage. If you have an electroplating shop that does tin plate, I would take it there. Zinc can also be done but it doesn't look as good as tin plate.

Otherwise a simple paint job with aluminum spray paint looks OK.

Yes, I have not been able to find one, so I bought this one in hopes of fabricating a stronger central part and attaching it to the outer part of this one. The channel changing knob will fit within the outer grip area of this fine tuning knob.

Dave

Mine also looks like his replacement, but I'm unsure if it's just that the wax melted off Bob's donut or there actually was a different one. I always figured it was original.

I was judging from the wider looking HV donut on his replacement flyback and its brightly colored lead insulators. Or maybe the old one discolored its leads when it died. Here is a shot of some numbers on one end of my flyback.

All of the original chassis mount caps tested open, leaky, or way off value. The "modern" (1977-ish) replacements that I had tacked in, way back then, all reformed nicely. I am not going to trust them, so I have started re-stuffing the old electrolytic caps with 105C caps. Here are some pictures of a few of them being re-stuffed. I have all but one of the chassis mount cans re-stuffed and I have started wiring them in. The 2700 pF door knob capacitor arrived and I think it will fit in the HV cage well.

Nice job on the re-stuffing!

I also use the same method, removing the can from the chassis and pealing back the rolled edge of the can to remove the tab ring. I much prefer this method over the method that cuts through the aluminum can above the base of the can. It's a lot more work using this method, but this method retains the original can in one piece, pretty much un-molested. And when re-installed on the chassis, it is hard to detect that it was re-stuffed.