#16
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No - the reason is because Predicta CRTs had a very short life due to a design flaw. In designing a very compact electron gun to make the neck of the CRT short, they ended up making a CRT with very poor life.
I suspect that Predictas were some of the shortest life TVs ever made, and the only ones that were run into the ground were those that had their CRTs replaced - something most owners would not do - especially on a set that was generally unreliable in other ways. My own Predicta (a Holiday) has a CRT that I got rebuilt by Metrocolor Engineering in LA in the early 1990s. It was probably the very last CRT they rebuilt. I had it done as they were basically closing their doors. They managed to short the focus grid to something else so I cannot adjust the focus. Fortunately the focus is pretty good in its unadjustable state. Last edited by Tom Albrecht; 10-26-2011 at 03:56 PM. |
#17
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I seem to recall reading on ARF that those sets had something like a 50% in waranty CRT failure rate, and that this essentially put them in such a bad state that the Ford buy out was pretty much an act of mercy.
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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 |
#18
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I figured I would add to this topic rather than continue in the CTC-4 one. This question is for Bob (ohohyodafarted) if he reads this: Bob, since the leaks in the CRT welds can be stopped (briefly) even by grease, has there been any testing of Vac-Seal? Is there a reason that product may have already been ruled out? (I would figure that if heat is the issue, is it reasonable to consider rebuilding the tube then applying the Vac-Seal as soon as it is out of the oven?)
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Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." |
#19
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Quote:
Last edited by stusnyder; 12-21-2011 at 08:25 AM. Reason: spelling |
#20
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Problem I see with applying any sealant to the rim of an AXP is that most tubes are a pretty tight fit into the plastic bezel, especially after the insulator is wrapped around it. I'd be afraid that the CRT would not physically fit into the bezel anymore after application of any goo, you'd have to be very careful how you did it.
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Evolution... |
Audiokarma |
#21
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The plus side of using the NASA stuff is it can hold up to oven temps.
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#22
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yes, but is it a good vacuum seal?
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#23
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I don't see any reason it would'nt be.. What exactly did they use to bond the glass parts to the metal in the first place?
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#24
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Sounds like the stuff NASA used was single-part? There are some amazing two-part epoxies out there right now.
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Bryan |
#25
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Well, for example, maybe it out-gases, but they don't care about that for tile adhesive.
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#26
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Whatever material you use to attempt to seal a CRT must have three propoerties:
1. It must survive the 600F oven temperatures during processing 2. It must have a thermal coefficient of expansion which matches very closely the glass/metal of the CRT 3. It must be impervious ie vacuum tight over a very long period of time. It is not easy to find a material which has all three of these properties. The most likely candidates are: 1. Nickel metal plating to seal the leaks 2. Frit glass to seal the leaks Bob and I have tested a high temperature epoxy with some success, but it has some TCE issues which may make it unsuitable. We continue to work the nickel plating and frit glass options. If anyone has any other suggestions, Bob and I would be interested in hearing them.
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John Folsom |
#27
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Quote:
A good example of what can happen if you don't heat glass uniformly is the couple of people who tried to remove cataracts from a 21FJP22 by using infra red heat lamps or a heat gun to heat the face of the crt; and by so doing created an large differential in the temperature between the front of the tube to the back of the tube, and thus causing an implosion. It is a big no-no to heat glass in a non uniform manner. In a crt rebuilding facility, the cataracts are removed by placing the entire tube in an oven and heating the entire tube in a uniform manner to a point where the PVA bonding adhesive becomes soft and then removing the safety glass while the tube is hot. Then the tube is allowed to cool in a uniform manner. When you remove a cataract in this manner, it is a fairly safe process and fairly simple.
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Vacuum tubes are used in Wisconsin to help heat your house. New Web Site under developement ME http://AntiqueTvGuy.com |
#28
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If the leaks are pores in the welds, wouldn't a metal with a liquid point of about 600F be in order? Maybe a metal used in solder like tin, lead if the kovar ring would allow it to plate the seam, sealing the holes.
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#29
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Thought about using tin plate, and I have a friend in the plating business that does tin plating who could do the work. However we decided on nickel, because nickel plating forms a self leveling homogeneous structure that is more likely to seal the leaks. Not all elements plate the same. Unfortunately my friend who does tin, does not do nickel.
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Vacuum tubes are used in Wisconsin to help heat your house. New Web Site under developement ME http://AntiqueTvGuy.com |
#30
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Quote:
No one could live with a 50% SCR, although bubble top failures exceeded historic levels for all other products. The 1960 models were much improved with a much better chassis and CRT design. HFII had a vision of Ford becoming another GM by adding a full line appliance line to compete with GM Frigidaire. Philco had new appliance plants in Indiana. Ford also wanted a fast way into the booming space industry, in which Philco had some standing. Philco's '59 and '60 TV lines had a full line of conventional looking products. The bubble tops were a product planner's scheme to differentiate Philco products on the showroom floor. They certainly did that. More bubble tops ended up in hotel rooms than living rooms. Don Last edited by Don Lindsly; 12-24-2011 at 01:50 PM. |
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