I believe you're right, Stan. I'd heard both explanations.
Actually, the geometry story doesn't pan out well if you've ever seen
one of the guns outside of the jug. the mesh is hemispherical in
shape. If it dealt with geometry, I'd expect an odd shape to
compensate for the extremes of the rectangular screen. For those who
have never seen one, it is interesting. Very, very delicate, and so
fine that when you hold it up to the light, it's like a diffraction
grating, splitting the light up into different colors. It's also so
fine that it will hold water. One little puff of air and you dimple
it permanently. I send a piece of a mesh to friend Dale Johnson
(used to work for Tek in the Dallas Service center, but at the time
was working for a company that serviced scanning electron
microscopes. He put the piece of mesh under a scope and the view was
really interesting. It's quiet obvious that it's etched and not a
woven screen that one first envisions. I don't know whatever
happened to the Polaroid of that scan that I had. It should would
make for an interesting post, but that was 25 years ago!
Sometimes, during manufacturing, a little dirt gets inside the jug
and finds its way to the mesh. The resulting display is a small spot
on the CRT that just can't be illuminated by the beam because of the
shadow effect it creates. I was rather irritated one time when a new
465B came in with that exact problem and the factory wasn't going to
honor a warranty replacement of the jug because it was "still within
all specifications of CRT anomolies". I put myself in the customer's
shoes and decided that I wouldn't put up with a something like that
in the windshield of a new car. Why should the customer put up with
a manufacturing defectlike that in his $3500 scope? We replaced the
CRT anyway and shoved the old one down factory's throat. Tek was
starting to change from a very customer-oriented organization to a
very money-conscious outfit.
And Stan, I don't know that I agree 100% about the mesh being a bad
deal compared to what the 535 had. I've never seen a burned CRT in a
scope with a mesh and you can't say that about the old ones. The
mesh diffused the beam enough that the CRT was pretty burn
resistant. To me, the ±1 digit bobble of a digital scope is far
worse to look at than the fuzzy trace of a 465.
Dean
