2 May
2016
2 May
'16
3:19 p.m.
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:
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?
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.