On 10/14/2015 08:55 AM, tony duell wrote:
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.
Yes, absolutely, on the Versatec 1200A. I put those motors
in a milling machine. Big, round case stepper motors, with
a ghastly resistor-transistor drive.
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 1200A did not have any mechanism for negative pressure
that I know of. The fountain was in the middle, then there
was a larger, rectangular region around it that returned the
fluid to the container. You could activate the pump while
the lid was open, with a button on the machine. The toner
would not overflow even with the paper away from the
fountain. Now, there was ONE way to make it spill. If you
opened or closed the lid while the drain space around the
fountain was still filled, the drying blower would spray
some of the toner. So, when the paper tore or some other
mishap occurred, you had to wait 10 seconds or so before
opening the cover.
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!
How could you do that??? Just the smell of the stuff should
have been adequate warning.
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 ;-(
The fact that the paper turned brown within a day or so just
sitting on the desk makes me think there would certainly be
no paper remaining usable for this printer. The same type
of system was used for some years after for making medical
quick copies on ultrasound and similar machines. Usually,
these were on about 5" wide paper, though.
Jon
