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

tony duell ard at p850ug1.demon.co.uk
Wed Oct 14 11:46:09 CDT 2015

[Versatec paper feed motors]

> 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.

You've got me worried now...

I have  V80. Actually, it's ICL-badged, and has a GPIB adapter board at the back 
connected to the normal parallel port [1]. I was prepared to swear the motor in
that is a normal DC motor, but perhaps I have misremembered it. I really don't
want to strip it down tonight, and finding the manuals [2] Is an even bigger job.

[1] This is a really odd board. It contains about 4 chips, one is a Fairchild thing
that does the GPIB handshake, etc. Another is (IIRC) 48 pins, and is some kind
of custom interface chip. I have never found out quite how the thing responds
to GPIB data, one day I will set it up with the PERQ (which I have software to drive
it on) and my HPIB analyser and take a look... 

The GPIB cable it came with had a 'barrier box' halfway along it. This was something
more commonly used with modems in the UK (in fact when you had to rent the modem
from the GPO it was actually required in many cases). A box with 24 inverse-series pairs
of zeners and 24 fuses to mke darn sure you coudn't overvoltage any pin on the modem.
Quite why it was needed here I don't know...

[2] Still unpacking after the housemove a year ago. Need to get the bookshelves up so I 
can unpack the 100-200 boxes of books...

> >> 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

Yes, that's like the V80, but I am pretty sure on that machine the 
'fountain' is on the suction side of the pump, that is it sucks from the outer
region. When there is paper present this causes toner to flow from the
bottle up through the middle bit, then back round the outside to the pump 
and back to the bottle. Again I might be mis-remembering things...

> > 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.

Got any better ways to unclog the pump? 


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