27 Dec
2006
27 Dec
'06
5:11 p.m.
Chris M wrote:
--- Chuck Guzis <cclist at sydex.com> wrote:
In the old days, the primary problem was loss of cathode emission. Cathodes
are made with a special coating (lovely stuff like barium-calcium-strontium
carbonates *) or alloy to get the electrons to fly off more readily.
Significant improvements in that area were made over the years, so it may be
that phosphor-light-emission loss occurs before cathode-electron-emission
loss these days.
The other trick in the old days was the picture tube booster, a small
autotransformer plugged in between the chassis connector and the CRT to boost
the filament voltage and run the cathode hotter. After the CRT deteriorated
further you might have it re-gunned.
(* If you look at the range of stuff that goes into a vacuum tube it's quite a
tour of the periodic table.)
In the "good old days", that's how
TV CRT's would be
recycled. Just
a new gun assembly and you're off and running. Of
course, nowadays
we just toss 'em into a toxic landfill.
I had thought the reason to go through this was so
you'd have fresh new phosphors. Them tubes get dim and
yucky after a while. But what do I know...