RCA 21CT55 B8802897 is Alive!

[holmesuser01]

I used to have a repair shop, and did home TV service for Sears for several years in the late 1980's and early '90's.

I have NEVER seen a color picture that looked as nice as the images you supplied us here on AK. Your set is incredible!

I could say that my CTC-12 looked similar, but I'd be lying a blue streak, and lightning would strike at any time.

Keep it up!

Bruce

[Tomcomm]

The RCA 21CT55 has been permanently installed in my lab, operating as a composite monitor for over a year now. It is powered-up occasionally and has retained its picture quality as posted previously:

http://s677.photobucket.com/albums/v...0TV/?start=all

I am really impressed with the awesome cabinet and chassis restoration performed by AK member Bob Galanter. His serial # B880 1131 is among the earlier production while my #880 2897 is very near the end of production. His is the 17th known survivor, mine is the 16th. What's the latest info on the other 15? Who has them? How many are operational? How many are being restored? Which ones are owned by AK members?

Seems these rare second RCA production CTVs are seldom discussed on AK except when a member starts a restoration or ends one. I welcome any replies from all 21CT55 owners or interested others, regarding their present activity and possible progress towards getting these ultimate roundies operational. I'm aware of at least six AK members that have indicated they have 21CT55s. I would greatly appreciate their replys to this request for current status information. Thanks......Tom

[Steve K]

Tom:

My 55 is in working order but still has some convergence issues. I have not had time recently to work on it but hope to get back to it shortly. I don't have the serial numbers here at work but can supply those to you later if you wish.

Steve

[Tomcomm]

When I first got my 21CT55 operational about a year ago, I replaced the two huge selenium rectifiers with a couple of 800PIV, 20A silicon diodes. This raised the 400v B++ buss from a sub normal 390v to supper normal 420v when operating from my local 115vrms mains. Everything worked OK, but I set my Powerstat down to 110vrms which lowered the B++ to 400v. It remained at 400v for all my convergence setup, picture quality evaluations and screen shots. the power transformer's surface was 124F at room temp of 77F.

I never had access to a HV probe for my VTVM so I always ran the Ultor control fully cw max. No problem with focus and the 6BD4 HV reg was running dark as expected. Last week I got two hi voltage spiral film resistors that added up to 940Meg. I was able to calibrate my VTVM to 4v on the 10v range when touching the probe to the 400v B++, indicating I now had a 100 to 1 voltage divider. I read the "boost voltage" at 980v without the probe and 9.7v with probe which translates to 970v or 1% low. I then touched the probe on the Ultor capacitor and got a reading of 34KV ! RCA specs the 21FBP22 at 27.5KV max. I checked the focus at 5800v. Sams and RCA sets the Ultor at 25KV, so I reduced mine to 25KV and had to refocus to 5200v but the convergence, both static and dynamic was way bad.

There is no X-Ray shielding or safety glass on this TV since 1964, when I destroyed the cabinet in going to vertical chassis. I wonder how much X-Ray I absorbed, if any? I could run the CRT between 25KV and 28KV but I must do a complete re convergence which is a real pain. Maybe the 34KV was causing the slight screen cutoff glow by activating the aluminized phosphor and reducing the ultimate black level in dark scenes ? Any suggestions?