For the noble gas idea to work, you have to know what the oxides will do with those gases present, and know for sure nothing bad can result as the moisture will remain because you have done nothing to deal with it. Bringing a HVAC vacuum and 90 degrees heat will cause the moisture to boil off as its boiling point is greatly reduced. Then if nothing more, you put the tube in a very thick heat sealed bag with a desiccant inside the bag of sufficient size to do some good, and then keep an eye on it as they change color with moisture (as they absorb it). How will you know if the noble gas leaks out ??

There is no reason why people here can't build a drying for storage box where you mail it to whomever needs it, and heat and vacuum the tube for storage, then bag seal it with desiccant for long term storage. You could get a local HVAC guy to run a vacuum on it.

Nice score.

Vans are nice. I couldn't even fit a 20" Zenith in the trunk of my '11 Impala today.

I have a line on a good 21FBP22, thanks to a helpful VK member.

I'm open to ideas about how to preserve this 21AXP22 in the meantime, although building vacuum chambers or bake boxes doesn't seem likely. My workshop is in an uproar during some remodeling and half its contents have already been evacuated into other parts of the house.

Phil Nelson

I don't think the phosphors are in any danger, as long as no liquid water got in there. That 15G RACS rebuild was a wreck and a half sitting around with no gun in it at all, and it's still working just fine to this day. If you wanted to be sure though you could cleave the gun out, then purge it with a slow flow of nitrogen over a few days to displace the air.

Hi Phil ,

In reading your post about not being able to easily build a vacuum chamber or bake box I got to wondering about the tube's physical position during storage . Specifically , would it make sense to store it in a position of having the screen up and the gun down , opposite of the normal way they come when new in their boxes ? (any new CRT I've ever unpacked was always "face down" in the carton)

I ask this with the idea that if there is enough moisture to rust the gun , and folks have mentioned possible phosphor damage , maybe with it stored screen facing up no moisture will be able to drip off of the gun and damage the phosphors ...

I'm not a good enough scientist to guess whether dripping is a possibility, or whether the rusting resulted from moisture in the ambient atmosphere. I could probably build a box with sturdy supports to hold it face up, if that seems important.

Whatever I do will need to be fairly low-tech. For instance, I could store it in a sealed plastic bag with some dessicant gel.

Phil Nelson

The gun isn't the problem, it's the shadow mask. If that has rusted or deformed, the tube's junk no matter how many guns you put in it. Getting the old gun out would confirm the extent of the damage, as you'll be able to see down the neck and have a look at the condition of the mask.

And yes, I can weld these tubes successfully. If there's a leak, it would be a lot easier to fix than on a 15G. With the 15G you'd have to frit treat the glass/metal joints first, then weld the metal seam of any pinholes.

Phill,

Leave it alone. Don't mess with it. Just put it in storage in your climate controlled home until such time as it may be a candidate for restoration. It is still sealed good enough that it is better than anything that you could possibly do to improve the situation.

Moisture is likely not the issue. The tube has O2 inside, and when the gun was heated via the filiment, the metal on the gun reacted with the O2 and caused oxidation of the metal in the guns elements. If the filiments had not been heated in the presence of the O2 in the tube, then it is very likely that the gun elements would not have oxidized.

Anyhow, no harm done. The gun is toast in any event and would need to be repaced or rebuilt if the tube is ever to be rebuilt after fixing the leak.

Best way to get a usable 21AXP22 is to wait for a clunker CTC5 to surface to steal the crt out of. The 5's still surface once in a while and I would personally rather have an opperational 4 than a clunker 5. The 4's have a better picture quality.. I have actually trashed a crappy 5 and made a 21AXP22 test jig from the crt, and associated cabinet components. Some day I will likely use the crt from the test jig to restore a worthy set needing a 21AXP22.

Be patient and sooner or later you will come by a decent usable 21AX for your director. I would presonally NOT do a retrofit with a glass tube. But that's JMHO, and my way of doing things. I would rather have a correct bad tube in a display set than an incorrect tube in a functioning set.

Thanks for the advice. If I can fit a glass tube non-destructively and watch the TV while I'm waiting to find the right tube, that would make me happy.

Does anyone happen to have the RCA factory manual? I have the RCA field service manual and an RCA service data supplement, but not the manual itself (Service Data 1955 no. T5). These docs (plus Sams) give me enough info to restore the set, but you never know what handy little tidbit another manual might include. I'd be happy to pay postage & a reasonable fee to borrow one for scanning.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

After replacing the electrolytic & paper capacitors, plus assorted resistors, the chassis passed the smoke test and has reasonable B+ and filament voltages. After I lay my hands on a couple of new tubes and oddball caps, I'll be ready to try more interesting experiments.

Looking ahead to when/if I get a usable 21FBP22, I gather that I'll need to fabricate a new HV lead for the CRT 2nd anode and make some provision to prevent arcing from the anode button area to nearby hardware. I'm hoping to use the same yoke and other neck whatnots, since nothing else is available. If that's a false hope, someone tell me now!

Phil Nelson

Last year there were at least two 21FBP CRTs for sale at the ETF so chances of finding one are good. Nick (AKA miniman) told me when I bought my set from him that on another CTC-4 he has for a time he had a glass tube in it and there was a scope HV lead that either worked straight up or at least had the correct plug to plug into the HV cage. I took the lazy path and used a salvaged BPC TV HV wire and carefully stripped a long section on the end of the wire, folded and soldered it until it would mesh with the female HV connector on the HV cage. and I sandwiched some thick plastic bags between the yoke and the HV connection on the CRT and the yoke.
It ain't the prettiest metal to glass CRT conversion, but it DOES work just fine.

You can do the metal to glass CRT conversion. Others have made it work in the past so there is no reason that you can't.

Tektronix scopes have the tower connection you need, but the glass tube anode does foul the yoke support causing arcing. You can try to insulate it somehow, cut the support to gain some clearance, or rig up your own crt mounting system.

Speaking of arcing, in the HV cage the 22-ohm resistor was burned and broken and the hood for the 6BK4A regulator tube was nibbled away, with evidence there had been arcing through the hood to the inside of the cage. I scrubbed the hood inside and out when I replaced the resistor and the electrolytics. Let's hope that puts an end to the fireworks.

Phil Nelson

http://antiqueradio.org/art/RCACTC-4...Unrestored.jpg

With a couple of new tubes, now I have great audio and decent sweep waveforms, plus a reasonable stair-step waveform at the video amp when I supply a color bar signal. Here's one of the horizontal waveforms:

http://antiqueradio.org/art/RCACTC-4FirstPower.jpg

Too bad my CRT is a dud!

Phil Nelson

Signs of life...I bet it makes high voltage, try it out.

Yah, it makes HV. This looks like about 19.5 KV. At the moment I'm running it from an Isotap at 110 VAC line voltage.

http://antiqueradio.org/art/RCACTC-4...ighVoltage.jpg

Had to scrounge for something to defeat the HV interlock. This cap from an old Disneyland pen did the trick!

http://antiqueradio.org/art/RCACTC-4...lockDefeat.jpg

This chassis seems very stable. I feel like I could be watching a movie tonight if I had a usable CRT. There are other things I can do in the meantime, but none of them half as fun as seeing that first image on the screen.

Phil Nelson

It really needs to be run at 117 VAC, that will stiffen it up quite a bit. Mine had the seleniums replaced with silicon diodes and a dropping resistor, so it's probably a little stronger than yours in HV production. I have mine set to around 24kv on the anode, but it will go much higher if you let it. Have you gone through the horizontal circuit setup procedure yet?

I haven't done anything besides power it up at reduced voltage and take a few readings while watching out for smoke. After the holiday, I should have time to replace the seleniums and start on all that other good stuff.

Phil Nelson

Thanks to the generosity of another VK member, I have a 21FJP22A with good emission. It arrived yesterday, in my homebrew CRT box that I shipped to him empty. He popped in the CRT and sent it back, and it arrived here in fine shape.

http://antiqueradio.org/art/RCACTC-4CRTBoxArrived.jpg

I haven't tried anything on for size yet, since the cabinet is completely disassembled, but I guess some people would cut a notch out of this retaining ring to avoid fouling the 2nd anode lead on the new CRT.

http://antiqueradio.org/art/RCACTC-4...ainingRing.jpg

It may be a while before I get to try out this CRT with the chassis. During our remodel, my workshop is packed into 100 boxes and temporarily piled in our new garage, which doesn't have power yet. Our living quarters are so crammed with overflow that I had to unpack the CRT in our front entry -- and then clear away all the mess before dinner guests arrived.

Phil Nelson

I previously posted this RCA production line photo to ETF. For those that have not seen them I'm posting them here as well. Phil, perhaps one of these is your CTC-4 "Director".

-Steve D.

Wouldn't it be cool if mine was one of those? Wonder what "adjustments" those experts are doing in the publicity photo? Checking to see if the top covers fit?

Phil Nelson

Good one Phil. The photog probably told them to look busy. Here's another photo of the CTC-4 production line I originally submitted to the ETF site.

-Steve D.

How much was the cost to ship the empty box?

Always wondered.....

SR

I cost just under $180 to FedEx the empty box coast-to-coast. It's the size that made it expensive; the shipper told me it could have weighed up to 200 pounds without increasing that charge. (UPS would have cost even more, if you're wondering). My box was about 2-3 inches taller than it really needed to be. I don't know if making it shorter would have gotten it under some size limit.

I couldn't resist setting the new tube into the cabinet and trying on the retainer ring.

http://antiqueradio.org/art/RCACTC-4...ainingRing.jpg

That anode connection is awfully close to the ring. Seems like you're asking for trouble (arcing) if you don't cut away some of the ring.

Looking ahead to when I really install it, the tube has an aquadag coating, so I guess that means fashioning a ground connection.

I don't have any use for the old insulating skirt. I wonder if it would be useful to cut away the bottom of the skirt and retain the rest (the waist, if you will) to go between this ring and the tube's neck and bell? I could even pigtail onto the old ultor connection -- which is built into the skirt -- to make the new aquadag connection. (I already cut off most of the old ultor lead to make my new anode lead.) That would mean cutting a hole in the skirt for the anode lead, of course.

On the other hand, if I butcher the skirt, I couldn't reuse it in the remote event that I run across a good 21AXP22 or have mine rebuilt . . . .

Phil Nelson

Interesting stuff.
For a dag connection use flat braided wire with a spring to pull things tight.
Anode is too close, cut out a large half moon. Insulate with a
piece of plastic with a channel, get from a 70's era Zenith. Others
may have used them, dont remember. They went on the DGS shield.

Use the large brown single wire anode connector from a Zenith tripler
like a 221-141-**. Very common & the heaviest anode I remember.
We used them for all replacements. PN's are 15-276 & 15-276-01
one has 2 holes for HV & focus divider & the other just one hole.
Most had a screw to put them on.

73 Zeno:smoke:

Sylvania published a brochure back in the late 60s about installing rare earth tubes in older receivers titled "Color Fidelity for Older Receivers". The part on CTC-4 showed a small portion of the skirt cut away from the anode area of a 21FB to allow for the connection of a compatible lead and boot. I scanned it, and have it somewhere, but not on this machine. I'll look for it tomorrow and if I find it I'll post it here. Should be an easy job to do, and will prevent arcing. I'm considering putting a 21CY in my CTC-4 but haven't yet made up my mind about that. :scratch2:
Good luck Phil!
Kevin

Phil,

When I purchased my CTC-5 Wingate, many years ago, the previous owner had already had the 21AXP22A tube replaced w/a 21FB22. RCA provided a conversion kit that allowed for the installation with a retaining ring that attached directly to the rear of the mask. No struts required and plenty of clearance room for the anode lead. I don't recall ever seeing another kit like this in other sets.

-Steve D.

Thanks, that is excellent information. I wish I could install the CRT and try to fire it up tomorrow, but with so many things packed up and no suitable place to work, that ain't gonna happen. At least I can try to collect the right materials in the meantime.

Phil Nelson

Phil,
I couldn't find the original brochure, but I did find a scanned copy in my CTC-4 binder. The scans aren't too good, but can be read. At least the recommended dimensions are given for notching the flange, along with advise about supporting the bottom of the mask assembly, as the glass tube is much more heavy than the 21AX.
Kevin

On my CTC-4 I was able to get away with not cutting the skirt and instead use a modern anode lead salvaged from a 90's BPC set and a few layers of thick plastic ziplock bag type material stuffed between the skirt and the HV suction cup. Back when I was active with that project it did not seem to allow any arcing or corona.

I feel it is best not to cut or modify any of the original mounting hardware as you never know when a good 21AXP might surface. Going with that thinking I saved the unmolested bell insulator as is from my set and refrained from cutting the HV lead to have the plug. I was able to make a decent HV plug by striping a good length of spare HV cable folding the wire neatly and tinning the strands together with solder....There are better solutions to the plug then I implemented, but my way does work.

With how perfect your set is I strongly encourage you to not do any thing permanent to mount a different type of CRT which may end up only being a temporary substitute.

Yes, I'm always in favor of the least-destructive solution. Today I laid my hands on a modern anode lead. Perhaps I will try that with some insulating layers between the anode cup and the metal ring (and one hand hovering over the power plug).

Phil Nelson

Good suggestion, Tom. I also would like to keep my 4 as original as possible. I installed a 21FB in a CTC-7 once, and used a Cool Whip top cut in half with GC high voltage putty between the halves. I wedged it between the ring and the CRT with great results, no arcing. I know Cool Whip is still available, but I don't know about the putty. I'm pretty sure a sub could be found to work. :yes:
Kevin

I tried using just a modern anode cap all by itself on my set before I had a good 21AXP22, but it would create random loud telltale 'snaps' as it would arc right through the silicone. 25kv ain't nothin to fool with, I would either cut the support you have or find a very slim anode cap and add additional insulation.

Yes, I had never lifted a metal tube before and I was startled at how much lighter it is than the glass counterpart.

I might be able to get that article through an inter-library loan (to make a better scan) if I can tell them the desired issue. As I read the first page, it is Sylvania News Technical Section, Summer-Fall 1965, volume 12, no. 2.

Phil Nelson

I think you can still buy Cambric insulating cloth from Antique Radio Supply. This stuff is great for HV insulation. I would put several layers of it under the bell and over the anode connection. This way you don't destroy anything original.

Any chance you could find a spare skirt ring from someone else's junker set to hack up and preserve your original?

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.

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.

I want it! I want it!! Yes, for real, I want it!!!

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:

http://antiqueradio.org/art/RCACTC-4...latingTape.jpg

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.

http://antiqueradio.org/art/RCACTC-4FirstLight.jpg

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.