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  #31  
Old 01-05-2009, 07:00 PM
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zenithfan1 zenithfan1 is offline
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I gotta agree with andy, the picture on this set is about as flawless as possible. I gave advise on the CR-70 in general, I apologize for not being more specific about this particular tube. After rereading your post Tom, I see a part I didn't pay close enough attention to. If it drops to bad on the life test, it's not the end of the world or a bad tube. At first, I thought you had a tube with a reading of 25%, not a filament drop of 25%, duh on my part. The life test is somewhat accurate but I wouldn't put too much faith in it. Any tube that tests good and equal on all three guns should be left be.
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  #32  
Old 01-06-2009, 06:22 AM
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excellent job of restoration! Congratulations.
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  #33  
Old 01-06-2009, 06:41 PM
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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
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  #34  
Old 03-30-2009, 11:09 AM
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Where Are They Now?

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

Last edited by Tomcomm; 05-30-2009 at 06:32 PM.
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  #35  
Old 03-30-2009, 12:35 PM
Steve K Steve K is offline
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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
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  #36  
Old 05-26-2009, 01:31 PM
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21FBP22 Ultor HV

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?

Last edited by Tomcomm; 05-27-2009 at 10:03 AM.
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  #37  
Old 05-26-2009, 01:52 PM
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Tom, as I think you are aware, I have a 21CT55 which has been restored. Last time I had it fired up, it needed some remedial work, and one of these days I will get back to it.
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  #38  
Old 05-26-2009, 03:49 PM
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Last edited by andy; 12-07-2021 at 01:45 PM.
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  #39  
Old 05-26-2009, 09:20 PM
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21FBP22A Ultor HV

Andy.........I used the wrong wording "the 6BD4 HV reg was running dark as expected" in describing the glow reflected from the tube's plate when running the CRT at max HV of 34KV. Obviously, it was pulling far less current and glowed less bright than it did at minimum HV setting of less than 25KV. This is typical of all shunt regulators. At all settings, it glowed brighter when the screen went black as it should.

My main concern is how much X-Ray did I absorb during the year of running 34KV with no CRT safety glass or cabinet screen glass? Is there any documented evidence that 21in CRTs running above 30KV has resulted in injury to those persons working in close proximity for extended periods of time? If so, what was the symptoms, and prognosis?
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  #40  
Old 05-27-2009, 03:26 AM
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Turn off all the lights in the room, if you glow in the dark, you're cooked.
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  #41  
Old 05-27-2009, 12:29 PM
Bill R Bill R is offline
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You are probably ok if you had all the High voltage shields in place. I was working on a GE set once with the HV cage removed. It gave me a really bad headache at first. Never did that again.
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  #42  
Old 05-27-2009, 03:31 PM
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Last edited by andy; 12-07-2021 at 01:45 PM.
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  #43  
Old 05-27-2009, 05:20 PM
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Quote:
Originally Posted by andy View Post
You shouldn't worry too much unless you spent years at close range. Has there ever been any proof that Xrays from TVs can be harmful?
Check out this site for the government's take on TV X-ray emissions:

US FDA/CDRH: CDRH Consumer Information - We Want You to Know About Television Radiation
Address:http://www.fda.gov/cdrh/consumer/TVRad.html

-Steve D.
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  #44  
Old 05-27-2009, 07:13 PM
roundscreen roundscreen is offline
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Hi Guys.
Sorry, But I do not understand this thread. Are you guys joking around?
Why would someone turn the high voltage up all the way on a vintage color set?
The high voltage should not be set over 25 kv on any round color crt made in the 60's and If the crt is something like a 21axp from the 50's it should not be set over 22 kv.if I recall correctly. Please be careful.
Ed
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  #45  
Old 05-28-2009, 10:31 AM
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No Joke Here

ED............When I first got the 21CT55 activated over a year ago, I had no way of setting the Ultor HV without a HV probe on my VTVM. I assumed the RCA engineers designed the HV portion of the CTC2B chassis to limit the HV control range to max spec for the 21AXP22 crt, somewhat above the 25KV recommended in the service manuals.Typical of my approach to design, I went for the max and left it there. Since I converted to the 21FBP22 in "64, rated at 27.5K to increase brightness, I saw no reason not to continue operating at max HV. The focus was in range and I got good convergence. Hey, it made great pictures didn't it?

Only last week when I hobbled-up a 100 to 1 HV probe and carefully calibrated it was I horrified to read 34KV Ultor or 6.5KV above RCA max spec! I immediately reduced the HV to 25KV and the screen looked terrible. I got it refocused but the convergence was way off. I then set HV to 28KV and the picture was somewhat better but convergence was still bad. Rather than getting into re convergence I simply returned HV to 34KV and posted this thread to get some expert advice. Maybe my junky HV probe is way off, but until I get a reading from a known commercial HV voltmeter I'm not going to go off screaming and mess up something that's working exceptionally well for over a year...Tom

Last edited by Tomcomm; 05-28-2009 at 11:08 AM.
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