Nice LAB11 brochure.

[Charles Anthony]

On Mon, May 2, 2016 at 3:19 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:

> On 2016-May-02, at 2:39 PM, Charles Anthony wrote:
> > On Mon, May 2, 2016 at 1:21 PM, Paul Koning <paulkoning at comcast.net>
> wrote:
> >>> On May 2, 2016, at 3:59 PM, Mattis Lind <mattislind at gmail.com> wrote:
> >>>
> >>> Yet another nice color brochure.
> >>>
> >>> https://dl.dropboxusercontent.com/u/96935524/Datormusuem/lab11.pdf
> >>>
> >>> Has anyone seen a VR20 in real? Rather interesting to be able to do a
> red
> >>> and green X/Y screen based on different energy levels. Someone care to
> >>> explain how that works?
> >>
> >> See https://en.wikipedia.org/wiki/Penetron.  The idea is that there are
> >> two layers, and a high voltage beam pokes through the first to activate
> the
> >> second.
> >>
> > I'm not sure that the Penetron is what DEC was using; according to
> > http://homepage.cs.uiowa.edu/~jones/pdp8/man/vc8e.html:
> >
> > "If the CO (color) bit changes because of the value loaded, and if the
> VC8E
> > is equipped to handle this option, a timer will be started to set the DN
> > (done) bit after either 300 microseconds (green to red) or 1600
> > microseconds (red to green). These delays correspond to the time taken by
> > the VR20 display for these color changes."
> >
> > According the Penetron wiki page, additional activation energy was
> provided
> > by a "set of fine wires placed behind the screen"; whereas the VC8E
> > apparently is setting the color by timing the beam.
> >
> > So yes, it seems to be an activation energy phenomenon, but not
> > specifically the Penetron technology. My physics fu isn't good enough to
> > explain how, but I would guess at some very non-linear phosphorescence
> > response.
> >
>
> Might have had to do with the time taken to switch the HV supply (for a
> Penetron) for the different penetration levels rather than a different
> phosphor-exciting scheme. Although, is that interface even at the scan
> level relating directly to the display tube, or at a controller level where
> it might be an artifact of the controller electronics?


Context: I have never seen any of these beasts, and I am a s/w guy that
dabbles in h/w. All of my opinions herein are derived from my reading DEC
documents to write vector display emulators. I may talking through my hat
here....

http://bitsavers.informatik.uni-stuttgart.de/www.computer.museum.uq.edu.au/pdf/DEC-11-HLPMA-B-D%20LPS11-S%20Laboratory%20Peripheral%20System%20Maintenance%20Manual.pdf

"3.4.6.2 Green Mode -- ... The intensify pule is used to intensify the
point on the scope.  ... approximately 1 us."

"3.4.6.2 Red Mode -- ... 6 us."

I can't locate any VR20 documentation, so other than pulse width input to
the VR20 I am unable to speculate further; it may well be that Penetron
technology was used, but the wording of the controller made it seem to me
otherwise, but I am more than prepared to be wrong -- it is perfectly
possible that the VR20 is controlling a Penetron based on the pulse width.

-- Charles