Dating rca post war tubes
In 1957 I was in the Drawing Office at Hammersmith, and was working on converting drawings for CSF Carcinotrons to the M-O V house standard. and the Z319 secondary emission pentode used it, too. So you now nask/scrape off the coating on the top end of the bulb . Different bulb shapes were usually based on economics. Say no more, Pat Cundy et al took over, and that was the gestation of the TT21 and its sisters.That KT66 link also shows a bulb with the grooves/scrapes where the locating micas contacted the glass. A quick splurge with a spray gun--you have an envelope carbon coated from here to eternity. It was cheaper to use one shape that was consistent with the types being made in the factory. Mike and I were both moved immediately to different sections. These are fired by rf induction during the very last stages of pumping.The U19 line was the only line handling top-cap bulbs at the time. The shapes and sizes and numbers are a reflection of life-testing showing up production problems.The girls lost some of their hourly productivity rate doing this. A single getter may look rinky-dink compared with a fat cup, or two Ds, two rings or two squares.Tetrode amplifier, triode amplifier/oscillator, gas- filled triode fire-atron! All M-O V tubes, at Hammersmith, and Gateshead, These were etched into the glass immediately after the visual inspection test. The M-O V sharp square date/type/factory marking was kosher, but there were loads of markings which looked dodgy; but were genuine. It may have been done by Hirst at Wembley, where life testing was done, or by the Dev. The production lines ran, on average, I guess, at 15seconds per tube.I remember blasting them with compressed air down a steel tube at 100psi, mounted in a "steel bullet" into a lead disc, 150mm diameter; penetration had to be no less than 6mm, and the little beggars had to test within 10% of original parameters! George Adamson, the production manager, (on these subminiatures, and the X78,and X79), a real nice guy, was always furiously one year behind becoming a member of the Institute of Production Engineers, as they raised the qualification levels every year. I handled a huge pile of returns at one point in my career, all were GEC/Osram manufacture, but the etching would have failed visual inspection at Gateshead, and looked like a kid with a white pen had drawn them! The Z77/6AM6/EF91/, for example, was running at one every 7seconds on each of three pumps, 24 hours a day at its height of production at Gateshead, as well as at Hammersmith.In addition to Hammersmith, I know that (older bottle style) KT66s were made at Shaw during WWII per Vyse & Jessop (2000), there’s even a photo of one from wartime Shaw display (p290).
I also obtained a copy of the original Williamson design brief and circuit, in its original blue duplicated form. ) Long gone now, after several house moves, and a divorce! Bryan Subject: RE: Re MOV/GEC/Osram codes and more Date: Mon, -0600Hi Bryan-Thanks again for writing me back the other day.One of your links to the KT66 showed a KT66 with a KB/L label. If the date stamp shows it to be after 1951, KB/L was CSF France! After I migrated to London, I got a copy of the Mc Graw-Hill/MIT book on Tube manufacture. In the Gateshead factory, we worked on reports from Hirst Research Centre for help if we had excessive failure rates. We used Dag80 at Gateshead on a number of trials on different types that needed rf screening or heat dissapation(disappation? N78/108, HN/LN309 spring to mind, and also the wonderful Z77(6AM6). Then they say, stuff the coating, try this carbon-coated nickel-iron or carbon-coated Ali.nickel stuff for the anodes. The carbon scraped off when the assembly is pushed in, is loose in the bulb, most falls out on the assembly line. The carbonates of strontium, barium do not like this. So, KT66s can have carbon coatings of various lengths in the bulb.CSF probably made KT66s for M-O V, too, as M-O V had a strong link with CSF, as well as RCA. There was no doubt that for heat disappation, it was the best thing, if it didn't scrape off and then contaminate the cathode coating when the electrode assembly was pushed up into the bulb. Two things can happen- the simple one is the loose blackstuff lowers the effective cathode temperature, and chemically, when combined with the rare-earth oxides a lowering of emissivity happens. A more expensive base glue in the Aquadag to make it scrapeproof, but not degas/degrade at high temperature. Some have none, using better heat radiating anode material.It has a very open construction, the cathode "seeing" a huge amount of the glass. Materials were variations of Bakelite and resin plastics. used on KT88 and TT21 types with their higher anode dissapation. I'm surprised that an E-type is available in commercial quantities, as it would have been given the prefix A when it went into production.The cheaper Dag-80 carbon coating was tried, and was a disaster; production line failure rate was huge, and life was reduced. I think that they may be bought in from another maker, and numbered slightly differently from the M-O V types. 1974 looks like the manufacture date on the pictures I've seen.