10 Feb
2011
10 Feb
'11
12:14 p.m.
The weekend before last, I picked up a Gould 5010 electrostatic
printer/plotter along with some PDP8 gear.
The technology is interesting. It writes an electrostatic charge
directly on the paper, and develops with a liquid toner "fountain" as
The name I associate with that sort of thing is 'Versatec'. I have a V80
on my PERQ, itworks just like that, building up a charge image on the
paper and then passing liquid toner over it.
the paper exits the machine. Mechanically, it's
quite simple, with just
a single stepper motor to advance the paper and a pump to recirculate
the toner. According to some patents I found on the web which appear to
match the configuration of the write head, the pins are activated by a
clever coincident-current addressing scheme that avoids the need to
It's conicident _voltage_, surely. Electrostatics tends to involve
votlges rather than currnets :-). Versatec did that too, with a row of
nib electrodes under the paper and a divided backing electrode above it.
That way several 'nibs' could be driven from one driver stage.
From waht I rememebr the electorde drives in teh V80
are custom hybrid
circutis, the same for the nibs and the back electrods. The
former
drives are referneces to logic ground, the latter to a
-ve-few-hundred-volts rail. I seem to rememebr optoisolated between the
inputs of thos drives (possibly there's a shift register involved to
reduce the number odsignals that need to be passed through isolatoprs)
and the rest of the logic.
dedicate a driver to each pin.
The product line was eventually bought by Calcomp, which continued to
manufacture electrostatic plotters into the 90's. A successor company
still provides paper and toner for some models, but the 5010 is not
mentioned on the website, and I have no idea whether supplies made for
the newer models will work in the 5010.
The printer looks reasonably good on the outside. Internally, there
are a few rusted places that could use cleaning and repainting, but it
doesn't look like it's structurally or functionally compromised in that
respect. The vinyl tubing for the toner circulation, on the other hand,
has turned brittle and most of it is missing, and it looks like there
White spirit (turps substitue, etc) seems to work well for cleaning up
the toner system in thse printers. I unblocked the toner pump in muy V80
by taking it apaart, soaking the tube parts in white spirit and then
trying the suck-it-and-see method. I 'saw' that the toner tastes horrible...
has been some toner leakage/spillage at some time in
the past. Most
distressingly, the electrostatic write head is gunked up and/or
corroded, and I suspect it is no good. The printer is a free-standing
Pity it's not a V80, I actually have a spare nib PCB for that.
unit, but not particularly heavy. Two guys lifted it
into the back of a
minivan without difficulty.
Before I strip this thing for parts (it has a couple of nice power
supplies, among others), is there any interest in it? Does anyone else
have such a printer and need parts?
This sort of comment botthers me. I guess it's because I am a hardware
guy first and foremost that I find something like this printer to be as
intersting as, a failry normal computer. If nto more so. Sure it's
useless for printing, but thento be fair a PDP8 is not particularly
useful for computing these days (sure, it's fun to restore, sure it's
educational, but it's not a number-cruncher).
I think it it were mine, I would get a lot of enjoyment geting that
electrostatic printer/plotter to run again.
-tony