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
Wed Oct 14 10:01:28 CDT 2015

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.


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