Mearuring a curved CRT tube

[Ummon]

What I'm really wondering here is whether a curved CRT is measured along an 'ideal plane', or if the actual curved surface of the tube is measured? Because, if it's the latter, then for example a 19" curved tube would be smaller than a 19" flat tube.

[grantspain]

a 19" curved and 19" pure flat are the same as the measure is made as dead flat on the diagonal from corner to corner
the only real time the curvature comes into play is how it affects the bezel
i.e a nanao ms8-29fan in daytona use if replaced with a wei ya 2929 will leave a gap in the bezel---which is why happ supply a bezel filler with the makvision tri sync monitor that they champion as a replacement

[Jack Burton]

Wouldn't a curved glass with a diagonal flat measurement of 19" have a slightly larger surface area than one that had a flat screen?  After all, the curved glass is taking a longer route to go between two points.

[grantspain]

Wouldn't a curved glass with a diagonal flat measurement of 19" have a slightly larger surface area than one that had a flat screen?  After all, the curved glass is taking a longer route to go between two points.

yeah but it is not important as it does not affect the size of the actual tube

[Jack Burton]

So is the glass on the other side (the side inside the tube) flat on the other side?  I'm just curious, I've never broken apart a CRT.

[Ummon]

I think it's concave, because otherwise you'd have issues due to refraction. That might imply flat tubes are convex inside, though. Hmmm.

[qrz]

So is the glass on the other side (the side inside the tube) flat on the other side?  I'm just curious, I've never broken apart a CRT.

it is the same as the face .  the reason flat crts have additional geometry circuitry, is due to the fact the electron beam will take a bit more time to reach the corners than center of screen.



some early tv crts ( < 1945 )  were round with a flat screen.   minor distortion was mostly ignored in those days.
see   http://www.earlytelevision.org/index.html

hey , a "good picture" was sometimes defined as seeing movement in the snow .   

if anyone cares,  the oldest tv i've repaired to date was a 1948 zenith.  was a very interesting set !

qrz