VT52s, VT61s lots of DEC and DG keyboards- return trip through Maine, MA, NY, PA, OH, IN to IL

Jon Elson elson at pico-systems.com
Tue Oct 13 22:27:10 CDT 2015

On Oct 13, 2015, at 1:22 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:

The Versatec electrostatic plotters are not the same as the VT52

>> printer, they are
>>> yet another process. WIth those the paper passes between a set of
>> electrodes that
>>> build up a charge image on the paper. I beleive the paper is specially
>> treated to
>>> make it more resistive so the charge doesn't leak away too quickly, and
>> there is
Yes, I had a bunch of Versatec 1200A's with the Tektronix 
hard copy feature.  the Versatec was the greatest graphics 
printer until laser printers came out, then they became 
instant boat anchors.  Here's the process.

There is a double-sided PC board that touches the face of 
the paper end-on, so the traces just come to the end of the 
board and make contact with the paper.  On the 1200A, that 
was a 200 DPI printer, so each side of the PC board had 100 
traces/inch, and they were interleaved, so you got to paint 
200 raster lines/inch along the axis of the paper.  The back 
side of the paper had wide electrodes that defined zones.  
One of these backplate electrodes was charged at a time to 
the opposite polarity of the front electrodes.  I seem to 
remember there were +800, -200 and -800 V power supplies.  
The raster line was written about one inch at a time across 
the page, then the next backplate was charged and the next 
inch was written, etc.  Once the whole line was written 
electrostatically on the paper, a stepper motor advanced the 
paper and the next line was written.  About an inch from the 
writing electrodes, there was a toner applicator that 
produced a fountain of this hydrocarbon-smelling solventy 
stuff with the carbon toner suspended in it.  The charge on 
the paper would attract the toner particles, and when the 
solvent dried (assisted by a blower) it pretty well stuck to 
the paper.  The paper had this awful chalky feel on the 
print side, the toner smelled like printer's ink, and when 
it was working really well, the paper came out gray with 
fairly decent print.

But, it was FAST!!!  It could print at about 1000 LPM in 
print mode, and if your computer could feed it, it could 
plot images (black and white only) at better than a page 
every 10 seconds or so.  So, it could actually run faster 
than most of today's laser printers - although the print 
quality, of course, was WAY worse.  And, with the Tek 
hardcopy board, it could hardcopy a Tek storage tube 
terminal in less than 30 seconds.

I still have some Versatec printed output, as I ran one here 
at my house for a couple years, from my MicroVAX.

We did have a TEK hard copy unit before the Versatecs.  That 
was a pretty awful unit.  it had a line-scan CRT with a 
fiber optic faceplate that exposed the image onto 
thermal-developing silver paper-film that rolled past the 
CRT.  It also made bad smells, and the paper came out brown 
with dark brown images on them.  In normal fluorescent 
lighting, the hard copies started turning totally brown 
after just a day or two.  Also, the silver paper was QUITE 
expensive, maybe close to a Dollar a page or something, even 
back in the 1970's.


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