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Re: Thick face plates
At 10:52 PM 4/25/95 -0700, Julius Friede wrote:
>Does anybody have any opinions regarding the thick face plate tubes on 3C's=
Yes. In general they seem to be a *good thing* for the following reasons:
1. Low flare characteristics which were considered to be an early plus for=
the URSA when it first appeared on the scene.
2. Crapola on the tube face is placed way outside the focal plane of the=
gate and thus contributes a slight shading error rather than a well=
focussed blotch followed by an inverse afterimage caused by the parallax=
error between the light emission at the phosphor and pickup of the tube=
dirt by the burn cell.
3. The positive electrostatic charge which would tend to accumulate on the=
outside face of the thin face CRT, and hence attract further dirt, seems to=
be minimised on the thick faceplate tube.
4. We no longer need a tube blower to constantly blow ionised air over the=
CRT face ( if you know anyone who wants to buy these from Editel, let me kn=
5. The phosphor appears to be set back further from the 45 degree mirror,=
necessitating a larger patch for the same scanned area on the film, and=
therefore less apparent tube grain. ( The same effect can be gained by=
moving a std. tube back in the cradle). I leave the drawbacks of the larger=
patch to be explained by the folks who use Metaspeed (try running at 100fps=
to see what I mean).
Possible drawbacks are:
1. Separation of the faceplate glass button from the rest of the CRT, on=
tubes manufactured in this fashion. (Rob L. and I had this happen with a TE=
tube in the middle of a session a year or so ago!)
2. Lack of flare "coma" around the CRT spot could tend to exaggerate tube=
phosphor grain, i.e. the result of the spot having a smaller half-amplitude=
3. Reduced light output. Anyone at Brimar, Tube Enhancements or New Century=
care to give us exact comparison figures on this?
4. Theoretically some dispersion of the light could occur ( i.e. the glass=
acting like a prism and smearing the spot into its spectral components). I=
have no evidence of this, but include it to be contentious.
Hope this gives you food for thought. Feedback, especially argumentative,=
welcome from other readers :-)=20