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#47
06-11-2015, 03:43 PM
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Quote:
For a few million $ start up costs the Chinese can probably run off all the 7JP4's and 3Kp4's we could ever need. We could do a Kickstarter campaign to raise funds. 
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#49
06-16-2015, 09:07 AM
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The issues with reproducing vintage CRTs (or other vacuum tubes) are multiple, and interdependent.
Most of the people who actually designed and built these things are at very least long since retired, if they are still walking the earth at all. A LOT of the process documentation (the "secret sauce" if you will) was landfilled when the production lines shut down decades ago. The RCA Vacuum Tube Design books are a good overview, but not complete. Many detailed formulas for phosphors, cathode coatings, etc. were the highly prized "IP" of the day, and were never made public. Most of the process machinery met the same fate as the documentation--landfilled or cut up for scrap metal. When manufacturers stopped building tubes, the specialized supply chain that fed the factories shut down immediately afterward. The exotic metal alloys, ultrahigh purity chemicals, specialized tooling, etc. that were needed to make QUALITY tubes suddenly had no market and just disappeared from availability. Many of these problems could be overcome with money, of course. But unless you are able to guarantee a consistent, ongoing demand for tubes, it will be difficult to get manufacturers (even in China) to gear up to go into production of the needed materials OR the finished products. Even the audio tubes that are still in production don't ship enough units to justify the supply chain commitment needed to truly reproduce the vintage stuff. And the musical instrument and high-end audio tube market FAR outstrips the potential market for reproduction 7JP4s...
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#50
06-17-2015, 01:57 AM
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I fear that N2IXK paints an accurate picture. Some parts aren't quite so bleak. Glassblowing skills are likely to exist for the foreseeable future. Glass to metal seals are also likely to stay aroiund. Some vacuum devices, such as photomultipliers, are still made in significant quantities, mainly for scientific research. I don't think Hamamatsu are ceasing production any time soon. Hot cathodes are still used but in specialist devices and small quantities.
Bringing all that together in the right form for making CRTs is another matter. Also there is little or no hope of making pressed (as against blown) CRTs from scratch as the tooling would be hugely expensive. All rectangular CRTs are pressed as were the later round ones. In the US, Ebeam and Thomas still exist but I don't think either is interested in our business. In the UK there's a company near London who I've spoken to. They are confident about being able to make blown CRT envelopes, can also do the glass/metal seals, but have no gun capability at all. Also in the UK Brimar (not sure how related they are to the original Brimar compnay) are still refurbing military and avionic CRTs. I don't think they're interested in us either. That leaves the excellent work being done at ETF and the German company whose cpabilities are currenty being explored. http://www.forum.radios-tv.co.uk/vie...hp?f=5&t=11174 The arts of CRT making aren't quite dead yet.
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#51
06-17-2015, 08:21 AM
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Ahh, the story of our CRTS was written a LONG time ago in a nursery rhyme that is now SO strangely apropos & prescient-"All the Kings horses, & all the King's men, couldn't put Humpty-Dumpty back together again.."
__________________
Benevolent Despot
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#52
06-25-2015, 10:13 AM
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Indeed, Sandy G. Very sad reflection on our times.
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