Homebrew PCBs

In a message dated 6/18/2003 1:21:55 PM Central Standard Time, 
gmanca101@... writes:

> I have an HP 7475A
> plotter that will never plot in alignment.

That kind of plotter may be fine for plotting graphics on PAPER, but I'd 
never consider one for plotting something that required the mechanical resolution 
of a PCB, particularly a double- or multi-sided one!  

If your need is "professional enough" that you require plotter-drawn artwork, 
then you must simply go BUY what you need!  

If your need is avocational, and/or only very occasional, the use of 
manually-applied Bishop Graphics PC-component patterns to 0.1" grid paper is not yet 
considered a mortal sin!  

An acquaintance who worked for a large chemical firm GAVE me a like-new 7475 
that his employer was "throwing out"!  I removed the cover to clean it with 
solvent, and dust-out the innards, and I saw that it moved the paper with RUBBER 
ROLLERS, and the quill across the page with a RUBBER "timing belt" with 
considerable "wiggle and flop".  And both of those axes were moved by little DC 
servo-motors with "shaft encoders" and custom "electronics".  This may have been 
an acceptable mechanism for moving a felt-tip pen about on smooth paper, but 
NOT for plotting something like PCB art!  NO way!  Now I grant you, I DID 
repeat the buillt-in Demo-Plot on the same sheet of paper, and it repeated all 
probably within 0.01", or even better---hard to tell, running a PEN about over 
paper!  I put an ad on e-bay, and sold it to an artist in a State far, far away 
in a few hours!   NO regrets!  

Jan Rowland


[Non-text portions of this message have been removed]