HP 7475A plotters are 'nearly' free (plus shipping) on ebay.  Search on
7475a.

Dave

Dale Botkin wrote:
>
> On Wed, 13 Nov 2002, Olin Lathrop wrote:
>
> > Back in 1980 I was right out of school and working for HP.  I wanted a way
> > to make my own circuit boards for personal projects like you guys are
> > talking about.
>
> 8< snip...
>
> I used to have an old IBM six-pen plotter (a re-labeled HP 7475, I think,
> B size flatbed).  I had excellent luck using a .5mm permanent marker that
> I found at an art store.  I had a cut-down HP felt tip plotter pen body
> that the new marker friction-fit into.  By setting the plot speed down to
> 1 or 2 inches per second, I got near perfect boards every time.  I was
> only making single sided boards, but I suppose with enough work one could
> probably get a double sided board done the same way.
>
> The plotter moved the pen in the X axis and the paper in the Y axis by
> means of a rubber lower roller and a grit-faced upper roller.  I did find
> I had to tape the PCB to a sheet of paper because the registration process
> was at high speed regardless of the plot speed you had set, and the
> rollers didn't grip the PCB material well enough to prevent slipping under
> that kind of acceleration.
>
> The pen was a common ultra-fine permanent ink pen, available in several
> colors from the local art supply joint.  Its only remarkable feature was
> that it was small enough in diameter to fit into an HP pen body that had
> the top and bottom removed so the pen gripper mechanism could hold onto
> it.  I used this setup numerous times with excellent results; the only
> reason I didn't mention it long ago is that old HP plotters are kind fo
> hard to come by any more.  I think I did mention this on the list a couple
> of years ago.
>
> Dale
>
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