VT100 flyback / geometry
ard at p850ug1.demon.co.uk
Tue Oct 9 16:12:16 CDT 2007
> First, the CRT in the VT100 is a M31-340W.
> On Mon, 8 Oct 2007, Tony Duell wrote:
> > Not according to my 1988 Philips CRT Databooks!
> > The coding is explained as follows :
> 1988 is pretty new... Did they really change the nomenclature of the
> tubes? I thought that
I have, alas, no idea if/when it was changed. I can try going back
through old books to see if anything turns up.
> > I've not seen a mgnetically-focuessed CRT since I repaired an _old_ Bush
> > TV. Old meaning System A, 405 lines. The focussing in that was controlled
> Well, System A was broadcast until the 80s ;-))
True. But system-A only TVs weren't still being made AFAIK. For a time
(late 60's, until mid 70's) we had 'dual standard' TVs over here with a
user switch to select between System A (405 lines) and System I (625
lines). There were even colour TVs that could display System A (in
monochrome only, of course).
> According to my tube books one of the newest magnetic focus CRTs for
> television sets should be the MW53-80 and MW61-80 (around 1958/1959).
> But they don't use fixed magnets, instead a focusing coil is used.
Some UK TVs did that too. Often the focus coil current was the cathode
(or anode) current of the audio output valve (!). But I've not seen one
of those for _many_ years, and certainly not in any computer-related device.
> > getting the convergence and purity right!), but nonoe of the monochrome
> > monitor service manuals I've read mention magnetic focussing. I've never
> > seen a yoke with anything other than centering rings on it.
> VT100 Series Pocket Service Guide, page 59/60.
OK, I will take a look. I am still very suprised.
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