Wanted: TRS-80 PC-2 Pocket Computer Plotter pens

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Thu Apr 17 18:56:57 2003

> Please post the source, if you find one. I have an Atari plotter
> and a Commodore plotter (model 1520) that use the same mechanism
> and the same pens.

There seem to be 2 types of mechanism -- the 4" (or so) one used in the
Atari, Commodore 1520, Radio Shack CGP115, Sharp MZ730 (I think -- it's
one of the MZ700s), etc, and the 2" (or so) one used with the Sharp
PC1500 and TRS-80 PC2. Apart from the obvious changes for the different
width (frame and platten roller) they are identical.

I believe they're made by Alps. I have the exploded diagrams and parts
lists for the 4" one, but the motor gears are not shown as a separate
part :-(

>
> What I could _really_ use is a source of the gear that fits directly

Couldn't we all!. This is a major problem with these plotters -- the
plastic seems to have been the wrong type, or the hole was made too small
(thus stressing the plastic too much when the gear was fitted) or
something. I think _all_ my plotters (a 1520, a CGP115, another
CGP115-like thing with the PSU internal, a couple of Sharp units for the
PC1500) have at least one broken gear.

> on the X and Y motor shafts. I have tried going to local RC car and
> model train shops, but they don't carry gears. This thread has come
> up before, but I still don't know how to sit down and accurately
> determine the physical characteristics of these gears to the
> satsifaction of a mail-order gear vendor. I can mic the shaft, I
> can count teeth, but the rest eludes me.

I will have to look up the exact procedure (the standard rules-of-thumb
may not apply in this case). It shouldn't be too hard to figure out...
Maybe then I should try and make either a brass replacement (which would
outlast the rest of the machine), or a lantern pinion type of thing (which
would have the advantage of not needing a special milling cutter to
make, but which strictly would need different shape teeth on the gear it
meshes with. That probably doesn't matter though).

-tony
Received on Thu Apr 17 2003 - 18:56:57 BST