Pre-war CRT in Dr Röntgen's rays

[ppppenguin]

Most CRTs are soft glass. Working on borosilicate glass (Pyrex) as used in some pre-war CRTs is much more difficult. When I arranged that 6/6 rebuild in 1986 the glassblower at Display Electronics was an old-timer who had actually worked on these tubes before WW2. He knew how to make a graded seal using 2 or 3 different grades of glass to match the original borosilicate to the new soft glass pinch. The pinch is the part that has the glass to metal seals. It would have almost impossible to save the old pinch. Making a graded seal is a very skilled job indeed. Making good glass to metal seals is a whole specialist field of its own. There's a lot about it in this book: "Barry Vyse & George Robert Jessop, The Saga of Marconi-Osram Valve: A History of Valve-making at One of the World's Foremost Enterprises, Vyse Ltd, 2000 ISBN 0-9539127-0-1"

Have a look at Glasslinger's Youtube videos. He (she?) has done some very impressive work. https://www.youtube.com/watch?v=GAMRHcbE3g0