On 2016-May-02, at 2:39 PM, Charles Anthony wrote: > On Mon, May 2, 2016 at 1:21 PM, Paul Koning <[email protected]> wrote: >>> On May 2, 2016, at 3:59 PM, Mattis Lind <[email protected]> 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?
