View Single Post
Old 14th Feb 2019, 3:46 pm   #23
Maarten
Dekatron
 
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,185
Default Re: CRT is brighter to one side [Hitachi CTP213]

Quote:
Originally Posted by InsertNameHere View Post
I saw a video a few days ago of someone replacing the tube in an American RCA set, or a Zenith, and he removed the front glass protective panel to clean it and had to cut through adhesive. Is this the same thing or slightly different.
That's something entirely different. Since picture tubes are high vacuum with around a metric tonne of air pressure on the screen and a bit more on the back, they were prone to violent implosion when struck by a hard object or otherwise subjected to mechanical stress. To prevent pieces of glass being ejected across the room (and into the viewers body), a separate piece of safety glass was required. Sometimes this was a flat piece of glass placed at the front of the cabinet, but US tubes tended to have a curved plate bonded to the tube. That was probably what you saw. Some time in the early to mid 1960's, it was discovered that a violent implosion could be contained by pre-tensioning the picture tube by crimping a steel band around the edge where the front and the cone of the tube are bonded, and the industry changed almost overnight. That's why you don't see separate safety glass anymore.
Maarten is offline