14 Oct
2015
14 Oct
'15
6:55 a.m.
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.
Only in the sense that a PDP11, or a VAX, or a PERQ, or
a <insert your favourite classic computer> is a boatanchor.
My view is that a computer is a lot more than the processor,
and that the peripherals should be preserved too. Yes the
processor runs the old software, but emulators do that too, If
you are interested (as I am) in the hardware then the peripherals
are as interesting as the processor in a lot of cases
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
That's it. IIRC that was the 'Nib electrode' in Versatec manuals.
Somewhere I have a spare one for the V80 series.
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.
It's been a long time since I looked at the manuals, but IIRC
the width of the back electrodes was half what you might
expect -- half the 'repeat distance' of the nibs. The reason was
to prevent edge effects between nibs and the adjacent back
electrodes.
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
Was it a stepper motor? I am sure mine uses a permanent magnet
DC motor. I do remember that the paper feed roller is in 2 parts
with a differential gear between them.
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
It's called the 'toner fountain' in the manuals, but it actually works
below atmospheric pressure. The results are that (a) the paper is
sucked down onto the toner fountain and (b) if the paper is torn
or runs out you don't get toner sprayed all over the machine room.
The toner is circulated by a little electromangnetic pump. The toner
system tends to block, I found that what we call 'white spirit' was a
suitable solvent to unblock it. One time I tried the old 'suck it and
see' method to get the pump valves working and found that the toner
tastes horrible!
[...]
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.
I don't have a Tektronix hard copy unit (one of the few oddball
printers I've not managed to obtain) but I am told that the paper
goes off with time, and that it unlikely there's any useable paper
left for them ;-(
-tony