14 Apr
2024
14 Apr
'24
5:15 p.m.
On Apr 13, 2024, at 5:48 PM, Jon Elson via cctalk
<cctalk(a)classiccmp.org> wrote:
On 4/12/24 20:21, Paul Koning via cctalk wrote:
Yes, there were a number of Versatec models for different paper sizes and pixel density.
I worked with a bunch of 1200A units, they could run either roll or fanfold paper at
11" width. The paper was clay coated and felt like a dirty chalkboard. The toner
was quite smelly, some kind of paraffin oil with carbon particles suspended in it. There
was a blower to evaporate the toner solvent. The 1200A had 200 pixels/inch, so you got
2112 pixels across the page, IIRC. it applied 800 V to the writing electrodes, and
something like 400 V to the segmented backplate that was on the opposite side of the
paper. It could print text at about 1200 LPM, which was pretty fantastic for the time.
But, I am glad to not have to deal with these things anymore!
Indeed.
Meanwhile, it turns out my memory was faulty. The printer I was describing sounds a lot
like the Versatec ones you mentioned, including the funny paper and smelly toner. But it
was actually made by Varian, and the driver tells me it had 1408 pixels across the width
of the paper, so at 11 inches wide that would make it 128 PPI. I wonder if I still have a
sample page or two from that printer.
paul
On Apr 12, 2024, at 7:48 PM, Van Snyder via
cctalk <cctalk(a)classiccmp.org> wrote:
... The other was to print on its "whippet"
printer, a very fast electrostatic printer that put soot onto a thermal
paper that was then heated to "fix" it. There was a huge variac under
the printer to adjust the heater. The perfect setting was between two
windings. Too cold and the soot fell off. Too hot and it was melted and
smeared into an almost illegible mess. But it was very fast -- and only
80 columns wide. It was about the size of a KSR-33.
Different beast, but it
reminds me of an electrostatic plotter we at on the U of Illinois PLATO system. That one
was by Versatec, either 11 or 17 inches wide (I forgot), 300 dpi, pretty sure it used wet
toner. It also used a chain drive for the paper feed, which had enough backlash that
starting and stopping would produce visible irregularities in the output. So I wrote a
driver for it that did overlapped I/O to avoid that problem. (File I/O directly from a
PPU program, lots of fun!)
With that, it did an awesome job printing musical scores.