On Wed, 13 Nov 2002, David Minkler wrote:

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

Ah.  Stupid me, I hadn't even looked.  Last time I did look for one was
several years ago, and they were hard to find then -- but eBay was barely
a startup at that time.  You can do this with any of that series of HP
plotters, I think I also used a 7470 at the time.

I can't tell you guys how nice this setup works, though.  The pens I found
are only a couple of bucks each, and I could go from layout to complete,
etched & drilled board in about an hour for a simple project.  Lines were
very clean, you just have to remember you simply can't do 8 mil lines with
4 mil spacing or anything crazy.  I did have traces between DIP pads with
no problems.

I didn't realize they were so common and cheap.  Wow.  This beats the hell
out of trying to modify an ink jet, trust me.  The standard pen body can
be used as a holder, just cut off the top, remove the guts, cut off the
tip just at the end of the large taper and slide in an ultra-fine marker.
All you have to be careful of is that you load the pen manually and bypass
the cover interlock switch so you can plot with the flip-up smoked cover
open to clear the tall pen.  Set the plot speed to 1IPS, plot a reverse
image and Presto!  Nearly instant PCB.  Only difficulty might be large
copper areas like ground planes, I seem to recall that doesn't work too
well and will require some manual touching up prior to etching.

Dale

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