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Originally Posted by InsertNameHere
If delta is a higher resolution, why did CRTs become PIL, or is that just for monitors, which could be capable of a better resolution when the user is closer to the screen?
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Once the manufacturing was perfected, PIL tubes had huge advantages, especially for set makers. They could dispense with large & costly deflection/ correction yokes and all the circuitry needed to drive them. Setting up the set was made much simpler and quicker.
If you've never seen the set up for a delta tube, I'll take some pictures of my Thorn 2000 which will show you how big the yoke is and how many convergence controls there are!
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What sort of mechanical stress can implode them?
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A brick lobbed at the screen by a 15 year old youth would do it!!
I grew up in a rural village and instead of driving the 20 miles to the tip, people just dumped TV's (and everything else) in ditches & gateways. Within days, there would be a sea of broken glass once the tube got stoved in.
In order for a CRT to work, it has to be pumped out (evacuated) to a near perfect vacuum when it's made. This means that atmospheric pressure (15 pounds per square inch) is trying to crush it. If the glass gets broken, all the air rushes in at once and the forces tear the glass structure apart sending glass flying everywhere.
That's why earlier tubes needed a safety glass in front to protect the user from flying glass (and to protect the tube from impact). Then some manufacturers adopted the bonded plastic screen guard detailed above.
Early CRT's were round screen as it's a 'stronger' shape to contain the forces. It took manufacturers a while to figure out how to make rectangular tubes strong enough. The Americans had colour TV quite a few years before we did. By the time we got it, rectangular tubes were being made.
All the best
Nick