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  #31  
Old 04-05-2016, 08:10 PM
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rca2000 rca2000 is offline
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But...what is the likelihood...of findng a GOOD GP22 tube--even IF it is NOS?

We ALL hear--or dream...about the tale of a whole SKID full of NOS GP22 tubes...long forgotten and waiting for their chance at glory in one of those sets..But even if there was TEN of these "NIB" tubes...how MANY of them...would actually be in VACCUM?
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  #32  
Old 04-06-2016, 02:28 PM
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dtvmcdonald dtvmcdonald is offline
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Another question is "if gassy ... is it a bad weld or a glass crack?" as the
former is fixable and the ETF will eventually be able to regun.
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  #33  
Old 04-06-2016, 05:48 PM
MRX37 MRX37 is offline
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So entertain me here...

A 15G can theoretically be regunned. The tricky part is those rare earth phosphors.

So theoretically the ETF might one day be able to build an all glass 15G replica. The phosphors might not match a real 15G but it would make a CT-100 watchable.

And I'm willing to bet that a phosphor formulation can be made to get the colors to match close enough that even CT-100 afficinados wouldn't be able to tell just by looking at it.

Last edited by MRX37; 04-06-2016 at 05:52 PM.
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  #34  
Old 04-06-2016, 06:30 PM
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I thought someone was working on removing the metal joint on a 15G and installing an anode connector
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  #35  
Old 04-06-2016, 06:38 PM
RetroHacker RetroHacker is offline
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I know there is an ongoing project to make an all glass 15GP22 - to the point of fabricating most of the parts. There is a write up about it on the Early Television website. Hasn't been any activity on it this year though - but, I mean, it is a long term, complicated project that requires a *lot* of care and a ton of research and testing.

-Ian
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  #36  
Old 04-06-2016, 07:37 PM
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Ongoing efforts to rebuild 15GP22s all involve using mostly re-claimed parts from existing tubes. Simply stated, the parts to build clone tubes no longer exist and would be very expensive to re-tool to build. Take for example the glass frontpanel and funnel, it would cost hundreds of thousands of dollars to replicate the special molds that originally produced these parts, and then you would have to get a glass company to agree to make the parts. Same is true for electron gun parts and rodding fixtures to assemble them into carefully aligned guns. Stem pins and molding fixtures to make the 20 pin base feedthrough, big dollars, as well. Phosphor deposition fixtures would also be expensive. Like Bob G. said, start up costs to produce these could run into the millions of dollars.

jr
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  #37  
Old 04-06-2016, 08:06 PM
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Quote:
Originally Posted by MRX37 View Post
So entertain me here...

A 15G can theoretically be regunned. The tricky part is those rare earth phosphors.

So theoretically the ETF might one day be able to build an all glass 15G replica. The phosphors might not match a real 15G but it would make a CT-100 watchable.

And I'm willing to bet that a phosphor formulation can be made to get the colors to match close enough that even CT-100 afficinados wouldn't be able to tell just by looking at it.
NO "rare earth" phosphors in a 15G. The avatar in this post shows original NTSC phosphors in an original 21AXP22. First generation 21AX.
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  #38  
Old 04-07-2016, 09:58 AM
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a possible rebuilt (in two years time) from etf might be around $3,000 dollars with out counting the failing rate. lets start saving for that>
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  #39  
Old 04-07-2016, 09:37 PM
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For a long time, I've wondered if it might be reasonable to make a few radical modifications to get some of these otherwise dead TV's up and running, even if it isn't authentic. There are tons of rectangular 15"- 17" tubes out there that were used in much more modern sets. It seems to me that you could modify the set to accommodate such a tube. Yes, the tube socket is different as is the deflection yoke and convergence yoke. Maybe I'm completely off base, but I somehow doubt it would be rocket science to substitute these components for the originals. Naturally, it would be important to save the original components in the off-chance that someone (like ETF) figures out how to rebuild the original CRT. I'm sure there would be some serious issues getting good geometry and convergence out of such a radical modification, but I'll bet it could be done, and still be reversible.

It's just a thought. I don't have a chassis to play with, but I think it is in the realm of possibilities. Many years ago, when I was a poor college student, I took the chassis from a Sears (Toshiba) clone of a CTC 10 and mated it with a more modern Curtis Mathis CRT and cabinet. It wasn't perfect, but it made an acceptable picture, which beat looking at a blank screen.

I have my asbestos underwear on, so fire away... :-)
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  #40  
Old 04-08-2016, 05:09 AM
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Heck, I even thought that there's got to be a way to (gulp) mount an LCD panel on the faceplate of a 15G tube to make it watchable.....either with or without using the original componentry.
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  #41  
Old 04-08-2016, 10:34 AM
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There's an old timer in the Detroit area who insists he worked on a CT-100 that was modified to use a later magnetic deflection tube. The convergence assembly and convergence yoke were replaced with parts from a later CTC-4 or 5, and the new CRT was connected to the existing 19.5 kV HT supply. The drive voltages for each gun had to be tweaked as well. He said it didn't work very well, and was really an enormous waste of time and energy.
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  #42  
Old 04-08-2016, 11:25 AM
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Even if all the electronic problems could be successfully solved, (the 15GP22 is 45 degree deflection and electrostatic convergence), very serious mechanical and aesthetic problems exist.

The large bezel visible from the front is *not* flat on the backside as are most bezels, there is a circular lip, about 3 inches deep and about 16 inches in diameter that is designed to support and insulate the ultor ring of the 15GP22. One would have to remove significant portions of the lip to install a rectangular jug or (gulp) a flat panel.

Aesthetically, it would be difficult to make the conversion look like the original...remember, the 15GP22 was produced before the process to deposit the phosphor dots on the curved inner surface of the faceplate panel was developed. What is seen from the front is a flat piece of glass with the phosphor dots deposited on it (screenprinted???)... this screen is mounted behind a metal bezel, and the whole assembly is supported *inside* the 15 inch glass faceplate panel, giving that unique appearance. Perhaps something like a porta-pottie jug behind a wooden bezel placed inside a glass 15 inch panel could replicate that appearance fairly well, but where would you get the panel? IMHO, the ugly *black eye* of a flat panel would not be a good choice, a real CRT would be much more appropriate.

I must admit that one time when the chassis was out of my set, I did slide a 9 inch Trinitron in and "enjoyed" the view for a few minutes but would never consider a retrofit, mostly for aesthetic reasions. The CT-100 is enjoyed for what it is/was, it does not have to produce a picture to earn its keep.

my 2 cents,
jr

Last edited by jr_tech; 04-08-2016 at 02:23 PM. Reason: correction, panel is closer to 15" not 16" as stated
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  #43  
Old 04-08-2016, 12:14 PM
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Agreed. Like I've said before, sometimes it's like unbolting a 13th century Norse canoe from the rafters of a museum and taking it out paddling in the Potomac. Some of them might hold water, some might not, but either way they can be appreciated for the historical significance they represent.
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  #44  
Old 04-08-2016, 04:51 PM
Tom9589 Tom9589 is offline
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As I posted earlier, The Henry Ford Museum has an 21" RCA on display with a flat screen shoe-horned into the original cabinet. It either had a 21AX or 21CY. It was not a pretty sight and was very obvious.

On the other hand, The National Center for Civil and Human Rights in Atlanta have a number of B&W sets with flat screens inside as well as one color set with a flat screen. All of these conversions looks fairly realistic.

I agree that it would be difficult to retrofit a CT-100 with anything other than a 15GP22 and make it look good.
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  #45  
Old 04-08-2016, 05:10 PM
MRX37 MRX37 is offline
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There's a store in Ferndale that has a Hallcrafter's roundie, and I did a double take until I realized they had mounted a 13" BPC TV in the cabinet
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