my RCA has one just like that :D

nice!

The 21AXP22A is at Scotty's and it looks like the rebuild will be attempted this week. He waits until there are several days with no predicted bad weather, since a power failure would cause problems with the oven.

I am still seeing if I can verify a list of caps for replacement. Doug drh4683 gave me a complete list, but I am still trying to locate them all and make up my order, especially a nuisance since RCA and SAMS numbered things differently.

Meanwhile, all I have accomplished is to remove the chassis and the CRT from the cabinet. I plan to remove the tubes and check them.

Any advice on cleaning the chassis would be appreciated at this point. Can this stand up to a wet cleaning, or should I not risk it? I know that is how Tektronix scopes used to be refurbished, but they also may have replaced controls or other things that I wouldn't want to risk having to replace en masse.

Congrats! You have been most definitely blessed! Can't wait to see more pics. I hope all goes well on the CRT rebuilding, my fingers are crossed.. Personally, I wouldn't do a wet cleaning unless there is no other choice. It may take more time to detail clean but it is better safe than sorry.

Clean chassis with compressed air jet and mild detergent in water soultion and a tooth brush. I would NOT use any more moisture than is necessary to spot clean with tooth brush to scrub and dry rags to wipe clean.

Did you send the original crt that lost vacuum to Scotty or did you find a dud under vacuum?

If you sent the original athat lost vacuum I would ask Scotty to seal the glass to metal seal with Vacseal prior to, and after the tube goes into the oven. It is a long shot but may help your rebuilt crt to hold vacuum.

Good Luck and let us know how the rebuild went.

Thanks for the advice. I popped for the vac-seal. Scotty looked at the tube and thinks the face and neck seals look OK - he thinks it most likely that the leak was at the metal evacuation pinch off. Of course, there is no guarantee, which I fully understand, but I am willing to risk the cash based on a reasoned examination. If it doesn't work, it's back to looking for a dud under vacuum.
I think everyone involved has their fingers crossed!

We who have attempted 15GP22 rebuilds have our fingers crossed for you!

[1] Fingers are crossed...

[2] Yes, there's something unseemly about a stream of water under pressure cleaning a valued chassis, but there have been no negatives for me so far, and I use it just as a first step before the hands-on cleaning and polishing.

Drying the wet chassis is important and I always use some combination of:

*wiping it with a cloth

*making sure the day is hot, sunny, and dry to 'bake' out the moisture (turning occasionally to get all sides and the bottom)

*and using a leaf blower to remove standing water and 'blow dry' the beast (this is the best way to remove moisture from hard-to-reach cracks and crevices).

Pete

I too use the hot water/pressure approach to cleaning a chassis. The only thing to be careful of is cardboard and paper. I've found that if the chassis is dried thoroughly, parts won't be damaged.

So for the cardboard and paper do you just wrap them up the best you can, or just avoid them? My 63 Zenith is pretty dirty looking, lots of dust. My 53 B&W Zenith is alot cleaner.

Scotty showed my some 15GP22s with obvious leak points - they look like filaments of air crossing the seal surface from outside to inside when you look from the front. Some tubes had a lot of them. No such obvious defects on the 21AX. He also tried a spark coil to see if he could get any sparking through the glass.

Testing tubes in the CTC-5, using a Realistic model 108.

I'm getting suspicious results on the 12AT7 color demods. The tester table says to use a quite low setting (4) on the "D" dial, which means a low reading for a given amount of current; that is, the tester expects a lot out of these tubes. Anyway, both demods read really low unless I increase the setting (I tried this because one of the types that could substitute requires a higher setting). Also, the reading jumps to a peak value when the button is pushed and them fades to lower values (easier to see if the "D" knob is cranked up).

Any ideas? Something wrong with the tester? A mistake in the settings table? I have tested about half the tubes and the 12AT7s are the first ones to behave this way. Found one dead 5U4 rectifier, otherwise the other tubes behave reasonably.

well, I found a couple of 12AT7's I bought last year for another project, and they test out OK! So, both in the CTC-5 were fried - must have made the color a little weak - but with the CRT dead I suppose it was dark too. So much for that recollection of it "working the last time it was turned on" :p:

I am amazed to see that Radio Shack once made an item like that. Times sure have changed, so much. Even as of the mid-70's when I started going to RS often and bought plenty of their kits and parts, I don't think they had anything close to a tube tester for sale.

Well, bad news on the rebuild of the aired 21AXP22A. Despite liberal use of Vac-Seal, and Scotty's optimistic examination of the aired tube, it did not achieve a good vacuum. Scotty reports that the gun looked OK after evacuation/baking (indicating not much air if any), but the getter flash looked abnormal, and now the tube shows internal blue glow under test. So, there's some unidentified small leak.

I'll be driving out to see it and retrieve it on Sunday. At this point it's not worth a second try without knowing where the leak is and whether it could be sealed for sure.

Sorry things are not going well, the set is worth the effort though. Hopefully you guys can figure it out or find a good AXP somewhere.

Oh dear. That IS bad news. probably does not bode well for the leaker 15GP22s, but then again, who knows? We still intend to attempt a leaker 15G, possibly on our next trip to Hawkeye.

On the bright side, let's hope there's a possibility of gaining valuable insight as to how early roundies leak.

Pete

To follow up on Petes suggestion, Wayne, you should ask Scotty if he can use his sparker (high voltage AC power supply) in an attempt to isolate where the leak is in the 21AXP22. Maybe this could lead to some insights.

He has tried it, but we will try again. I'm driving out tomorrow and will see Scotty on Sunday, so I'll have an update hext week.

Here are a couple of pix of the tube at Hawk-Eye. Scotty and I jawed a bit, and he's willing to house it for a while in case the geniuses here (you know who you are) come up with more ideas. Scotty didn't apply Vac-seal to every possible place, plus there may be other things we could do, so thinkin' it over.

The close-up with the Tesla coil shows the "blue glow" (photographs more pink) due to residual air. Scotty says the leak is big enough that he can notice a change over the last 2 days. Eventually, the HV will just make arcs between the electrodes when enough air gets in.

Just curious: cured vac-seal is evident at the glass-metal interface in your photos; did Scotty also vac-seal the faceplate?

Pete

I thought so too, but Scotty said he only did the faceplate, not the bell.

Now a question on what to do in the meantime -
What does it take to replace the metal-cone 21AxP22A with a glass 21FBP22? Can anyone describe a good way of mounting a glass tube, preferably in a way that would allow going back to the original should one appear?

I can imagine making a cradle out of straps of some kind, but if the shroud has to be removed, I'm not sure how the yoke should be supported. With the factory setup, the yoke is actually clamped to the shroud, not the neck.

21FBP22 Replacement
 

Sorry for the late reply, I've been working on my own computer system hard drive diaster since the 1st of the month. Lost all my Healey and 21CT55 photos so can feel Wain's disappointment with the CTC5. I replaced the 21AXP22s with 21FBP22s in my CTC4 and CTC2B in early 1960. They are both mounted the same with four struts running from the yoke assembly to the cabinet front structure. The 21FBP22's glass envelopes were wider than the metal coned 21AXP22s so the plastic insulating shroud had to be cut away from its front mask bell and the struts had to be lengthened and remounted to the cabinet's front wooden structure. I used screw-eyes screwed directly into the wooden front. Since I'm not a restorer, this hack was fine with me

I realize the CTC5 uses the plastic shroud to mount the yoke assembly and support the CRT. If it can't be modified maybe the strut and screw eye scheme will work for you. What do 21FB's sell for these days especially the rare-earth A version? Replacing the 21AX's with the 21FBs is the way to go, you won't be sorry..........Tom

One disadvantage of replacing a 21AXP22 with a 21FBP22 or other all glass color CRT is that you give up the superior colorimetry of the 21AXP22s phosphors.

Interesting adaptation. I also have received pix of an original RCA kit, which is somewhat different, and includes a plastic back plate for the yoke so it can be clamped and supported on-center by the CRT neck.

I don't want to hack up the cone, in case I would get a 21AXP to install later. Also, as John Folsom says, one of my main reasons for restoring the set to operation is to look at the color rendition with the original tube.

Any mechanical engineers want to join this project?

I'm new to this, so I'm not very familiar with how this board works. It seems there're a lot of very knowledgable folks here. I have an RCA CTC-11. Has run well for many years with easy fixes (replace a tube here and there, etc.) It's starting to need some caps, etc. And I'd like to replace the flyback. Where is a good source for these parts. Also, does anybody have the service manual or any service information for the CTC-11. Thanks. Dave

Hi Dave,
Welcome to the forum, It's always nice to see another TV guy join the group. I'm sure someone here has what you need. But, it would have been best for you to have started a new thread about your issue. No biggie though, I made some REAL goofs around here when I first came, still do sometimes.LOL. So, that said, just start a thread about your 11. I would like to see pics. Also, look up Moyers electronics. They might have a fly for you. Try JustRadios for caps, they are reasonable and have a good product.
Mark

I don't know how to start a new thread. I'll try it now. I guess I have to give it a title. I'll try "RCA CTC-11."

Mark:

Thanks very much. I think I was successful starting a new thread. I still don't know how to navigate well. I have pics but I don't know how to post them yet. I'll do it under the new thread when I figure it out.

Thanks, Dave

Update - I've got dibs on a 21FJP22 (glass tube), but I haven't quite figured out how to mount it. I got info on how the factory mounting kit worked, but it involves a mounting adapter for the yoke that I'm afraid I couldn't duplicate. I also got info on modifying the existing insulating cone to mount the glass tube, but I don't want to hack it up, just in case I might get a working 21AXP22A in the future. So, still scratching my head a bit. I found a 17-inch diameter poly funnel on ebay that might be possible to cut down to make a mounting collar, but it wouldn't hold the yoke.

Meanwhile, I have ordered some replacement small tubes, film caps to replace the paper caps, and new 'lytics. It's moving slow, but moving.

I wonder if a newer 21" yoke would be compatible with that chassis? I would think someone would have a spare sitting around, something from a CTC-11-16. I don't know that they changed them up any over those years.

i have a nos yolke for the later roundies. steve

sent you a PM

Update - I picked up the rebuilt 21FJP22 over the weekend. Now taking a good look at how I might mount it. It's less a question of knowing what I might want to do and more of how I can do it myself with nothing in the way of shop tools. I would not like to do it the way Tom did for a couple of reasons:
- The existing yoke mount is part of the poly cone in the CTC-5, not metal like Tom's pix;
- The example pix I have of a CTC-5 with factory kit show a metal shroud that is near the face of the tube and therefore away from the HV connector.

The shroud, which apparently is what holds the tube to the bezel, has four metal tabs that are screwed to the existing mount points for the 21AX, so the tie rods are not needed. It also has the yoke supported by the neck of the tube, so it seems the support by the cone is not needed. I tried the yoke on the 21FB neck, and while it's slightly loose, it seems like a small bit of shimming will fix that.

Now my problem is to figure out how I can fabricate the equivalent of that mounting kit.

Of course, if a good 21AXP22A would show up..... :)

Still working through cap replacements - replacing paper/wax caps with film types.

I got to the .047 600V that is across the line. I know this needs to withstand whatever mother nature and the power company might throw at it, so I'm wondering what exactly to use to replace it. Any suggestions?

I no longer replace the power line decoupling capacitors in sets. I simply remove them, along with any resistors from line to ground. I have not found operating old sets without these components causing any problems. This also seems to reduce the mild shock hazard this connection from line to chassis provides.

If you decide to replace it, go to www.justradios.com. They sell "safety capacitors" that are designed for this purpose. Of course, you could try the set without it, like has already been suggested. I've got many radios from the late '20's and early '30's with no line bypass cap and they seem to work just fine.

Thanks for the link - I just took a look and also will check them out for any others I'm missing.