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#91
11-24-2014, 01:21 AM
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Excellent news.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did." 
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#93
11-28-2014, 06:23 PM
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Re-using a cathode After its been in air
Apparently it IS possible....
But--At all times the cathode is down to air--it MUST be kept above 100 deg C, as its moisture that damages it, not the air itself.... The Heater could be used for this...... I was reading something about Electron Microscope cathodes and the issues they had with them and their longevity/changing/re-using them etc.... Whether its worthwhile/worth the risk, going to the trouble of breaking a tube open to use its gun in a rarer tube by doing this--that would be up to the rebuilder/owner of the tubes....
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#94
11-29-2014, 02:55 AM
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I don't thhink an oxide cathode (as used in all CRTs we are likely to encounter) will survive being down to air. Pure tungsten and thoriated filaments may well do better but these were superseded in receiving valves in the 1920s. Now only used in some transmitting and high power valves.
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#95
11-29-2014, 03:18 PM
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The article was very specific....
60/40 Thorium/Barium Oxide Coated Cathodes--as used in the majority of CRT's--and certain Electron-Microscopes..... The art was to keep them hot therefore attack from moisture eliminated.
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#96
12-07-2014, 05:05 AM
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#97
12-07-2014, 10:34 AM
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Very good.
Has the shipment from RACS arrived?
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#98
12-11-2014, 02:55 PM
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Quote:
Filament life in an EM is typically 50 hours or so and the vacuum equipment is designed for easy filament replacement using simple tools. The short life is also a function of cycling EM filaments by exposure to air at lower vaccum (poor vacuum) 10-4 torr to 10-7 torr conditions without the use of getters or baking. LN2 (liquid nitrogen) traps are somtimes used to help remove water vapor. Unlike the EM, a CRT design typically requires complex sophisticated equipment to replace the cathode emitter and gun assemblies need to flashed with getters. Assembly also requires baking to outgas everything inside the envelope - mainly to drive off water vapor and dissolved gases quickly. However, the payoff, if done right, is an extremely high vacuum 10-8 torr or better, with continuous getter activity over the service life of the CRT, which in some cases can be decades - if you get all your sealing surfaces air tight! That's a big 'if' with frit and glass to metal seals. Most SEM and TEM (scanning and transmission electron microscopes) use solid tungsten wire filaments. The wire is bent sharply to form a tip to form the cathode emitter. For smaller spot sizes and higher brightness (more electron emission) EMs can use LaB6 (Lathanum Hexaboride) emitters. The LaB6 has a unique ability to physically have a sharp tip compared to a tungsten filament that when heated has a fairly low work function for very fine stream of electrons. In this configuration, a single crystal of LaB6 is supported and heated by the tungsten wire. Heat from the tungsten wire causes the LaB6 to emit thermionic electrons. As an fyi. Pure tungsten and LaB6 cathode filament heaters are often held by posts of MO and RE for support. The tungsten wire is spot welded to the substrate posts, which also acts as conductors for the filament current used to drive up the temperature of the tunsgten. As used in electron microscopes they are typically stored at atmosphere and long term storage. They are not affected by temperature or humidity. It's not required to keep them in a desiccator. Tungsten and LaB 6 will rapidly outgas when gradually heated initially prior to bringing the emitter up to full operating termperature. That process may take several hours. Here's a link to various emitters used in electron microscopes (SEM and TEM) https://www.google.com/search?q=lab6...Q&ved=0CCoQsAQ
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#99
12-12-2014, 03:19 AM
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Excellent news.. I'm glad everything arrived undamaged..
__________________
Looking for an all tube or hybrid color TV set from the late 1960s, early 1970s that's in a steal cabinet..
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#100
12-12-2014, 12:47 PM
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Hi to All,
RACS shipment to the ETF: For those who haven't seen Steve's photo on the ETF site, here is the first photo of the container's content which arrived at the ETF on Dec 11th. (Thanks! Steve for the pix and all the hard work to make this happen). The 2 page listing displayed below list the content. The numbers refer to pallet numbers and carton numbers, not the quantities of stuff inside. If an exhaustive listing had been required, for instance for gun models, etc. the manifest would have been 20-30 pages long. Total weight of the shipment was close to 4 metric tons. Come to the 2015 Convention! you will see everything with your very own eyes. Best Regards to all and Merry Christmas, jhalphen Paris/France
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#101
12-14-2014, 07:27 AM
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The equipment is at the Museum. Thanks to Jerome for all his help.
We have just started inventorying the stuff, but so far the biggest pleasant surprise is hundreds of cathodes and about a hundred filaments that are perfect for our color and black and white rebuilds.
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#103
12-17-2014, 01:47 AM
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Very nice to hear that the equipment has arrived safely at the museum.
"Return to USA of RCA non-processed CRTs". This sounds like the answer to the question I first asked last February in this post: http://www.videokarma.org/showpost.p...6&postcount=11
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#104
12-17-2014, 07:11 AM
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Hi Chris,
indeed, this line item describes the 10x 15GP22's sent by Molnar/Galanter/Folsom jr/Kubbe to RACS. I have asked Steve, as he unpacks the shipment, to make it a priority to check the condition of the returned tubes and inform their owners. No news yet, but 4 tons is a lot of stuff to unpack. From memory, 4 tubes were processed, some had up to 5 frit applications + oven passes to try to solve the Anode ring leakage. Also from memory, one tube has a new gun installed, is under vacuum, and from RACS's quote before the shipment left France, the Getter was still silver. The gun was not activated because if the tube leaked, the gun could be retrieved without having to replace again the Cathode and Filament. Best Regards jhalphen Paris/France Last edited by jhalphen; 12-17-2014 at 07:18 AM.
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#105
12-17-2014, 07:33 AM
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We are still unpacking. There are 6 tubes in a crate which we haven't inspected yet. Of the 4 in boxes, one has a broken face and the other 3 look fine.
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