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#77
02-22-2014, 11:19 AM
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Sure, if someone has a spare metal retaining ring, I'd be delighted to use that in place of mine. On the other hand, this was a "factory approved" sort of modification, which seems less objectionable than hot-rodding an old TV. If I just cut an arc out of the ring, it should still work to support a much lighter 21AXP22.
That cambric insulating cloth sounds interesting, but I'm not finding it on the AES website. 3M makes a varnished cambric insulating tape that's rated for 69KV but quite expensive. This 3M splicing tape is also good for 69KV and cheaper: http://www.grainger.com/product/3M-S...omCatalog=true If you don't remove a piece from the retaining ring, I guess the idea would be to get as much insulation as possible in the small space between the anode button and the metal ring. You could also put insulation under the retaining ring to isolate it from the bell of the CRT. As I understand the original setup, the big ring with the convergence magnets connects to ground, but the retaining ring and yoke support are left to "float" electrically. They are insulated from the CRT by the big plastic skirt, and the long retaining stays connect to the wooden cabinet with staples anchored in thick ceramic (or plastic?) washers. Phil Nelson P.S. I just remembered that I have a little jug of corona dope somewhere in my boxes of stuff. Last edited by Phil Nelson; 02-22-2014 at 01:40 PM. 
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#78
02-22-2014, 09:43 PM
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It shouldn't take much insulation. Remember that the plastic ring that is around the rim of the metal tube is less than 1/8 inch thick.
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#79
02-25-2014, 05:42 AM
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I want it! I want it!! Yes, for real, I want it!!!
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julian
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#80
02-27-2014, 12:28 AM
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I couldn't resist messing with the set a little. Steve was right, it didn't take a ton of insulation. I cut a small notch in the retaining ring and covered the edges with a few layers of this tape:
 The 21FJP22A tube survived its cross-country journey and it lights up OK. Strangely, I somehow lost signal since the last time I powered it up on the bench, when I had nice audio and I could see a video signal (with a scope) at the video amp.  No doubt it is something simple, but it's too late to investigate tonight. Anyhow, the CRT conversion was simpler than I expected. Phil Nelson P.S. No, I haven't yet played with purity adjustments or any of that other good stuff. Last edited by Phil Nelson; 02-27-2014 at 01:01 PM.
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#81
02-28-2014, 05:50 PM
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Quote:
 Injecting a video signal at the video amp gives me a faint picture.  Injecting an IF signal in the IF strip also gives a (fainter) picture.  Subbing the 6X8 and 6BQ7 tubes in the tuner changes nothing. I still get absolutely nothing from the tuner -- no static/scratching when you change channels, nada. I guess the next step is to pull the tuner and try some cleaning. I'm still at a loss to see why the signal suddenly disappeared. There are no obviously torn-loose wires, etc. I posted the Sams manual here for anyone who's curious: http://antiqueradio.org/art/RCA-CTC4-Sams-314-9.pdf I believe the schematic from my RCA field service manual is more accurate, but I don't have a scan of that. Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html
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#82
02-28-2014, 06:34 PM
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Try wiggling the IF and AGC tubes, and adjusting the AGC control. Part of the reason I shelved mine mid-resto (asside form it needing and alignment that I'm not equipped for or experienced at) was that the IF sockets in mine were intermittent and so was the AGC...I could loose all signal if it was in a bad mood on a given day.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#83
02-28-2014, 07:10 PM
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Wiggling every tube in sight got me nowhere, but after cranking up the AGC control I'm getting a healthy scratch (visual & audible) when I change channels. Maybe cleaning the tuner will help. I don't see any easy snap-off panel that can be removed. I guess you need to unsolder the connections and remove the whole tuner assembly.
Phil Nelson P.S. I did go through my usual routine of cleaning all tube pins & sockets at the start of this project. I suppose it can't hurt to re-clean the sockets in the tuner & IF, etc.
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#84
02-28-2014, 09:01 PM
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IIRC I was able to clean my tuner without electrically disconnecting it, but it has been about 3 years since I did that....I think a number of screws have to be removed to get the cover off.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#85
02-28-2014, 09:05 PM
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Sockets were the culprit in mine as well, so that makes 3. I also had an AGC pot that was smoked, that sure didn't help. I'm still trying to get my audio back, I lost it at some point and it's been on vacation ever since.
To fix the sockets, you can sort of repin them with new contacts from another socket. You have to be careful and do them one at a time in situ, but when you're done the job is worth it not to have bum connections on the PC boards.
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Evolution... 
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#86
02-28-2014, 09:20 PM
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Quote:
I'll have to test the AGC pot when I get back around to my CTC-4.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#87
03-01-2014, 04:46 PM
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Vigorous socket re-cleaning changed nothing. Next stop, Tunerville.
 Removal meant unsoldering ten connections, but they were all easily accessible. I will carefully clean the contacts with swabs and liquid DeOxit. Phil Nelson Last edited by Phil Nelson; 03-01-2014 at 05:27 PM.
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#88
03-02-2014, 03:35 AM
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If the video amp is after the tuner, signal path wise, why would a weak picture(while injecting at the control grid of the video amp) mean that the tuner was bad? Not saying it isn't, I'm just not following the sequence of events I guess.
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#89
03-02-2014, 12:55 PM
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I was just walking backward, doing a very basic check to see what sections could pass a signal. Seeing a picture when I injected video at the video amp suggested that things downstream from there were working (at least marginally). Seeing a picture when I injected an IF signal at the IF amp suggested that things downstream from there were working. So, the no-signal problem was likely between the antenna terminal and the IF strip.
The solution was simple, after all, and it turned up when I serviced the tuner. The UHF-VHF switch in back of the tuner was funky and it had stuck in the UHF position. Here is the switch working normally:  I'm not impressed with that switch, or the quality of the tuner in general, but it's all clean and operational now, and I can get a picture through the antenna input.  And now for that Wizard of Oz photo you've been waiting for!  Yah, we're a long way from a good color picture, but the CRT transplant was successful, knock on wood, and I think there's hope for the old girl, after all. Now to read up on CTC-4 setup procedures . . . . Phil Nelson Phil's Old Radios http://antiqueradio.org/index.html Last edited by Phil Nelson; 03-02-2014 at 01:20 PM.
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#90
03-02-2014, 02:58 PM
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Looks like they could have done a little more work on the design of that switch....
Movement to the right those contacts hardly get anything to stand on.... Anyway, nice job on the animated gif.... Have you not degaussed the tube yet? or not done any purity? <-- Sorry re-read above posts... Nice bright tube though.... If you come across an original tube, will you put it back in...?
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Yes you can call me "Squirrel boy" Last edited by Username1; 03-02-2014 at 03:03 PM.
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