How to refurbish plotter pens?

[Mattis Lind]

A late follow up on this topic.

I got my IBM 1627 running. Actually it is not mine, it belong to my father
that got it used for his home built computer somewhere around 1977. It
became a project that never was finished... There are still some simple
drawings he did on how to interface it.

http://i.imgur.com/8JK8wwO.jpg
http://i.imgur.com/8YJA0Qb.jpg

First thing I recognized was that the Mallory FP type capacitors in this
one both measured below 1nF capacitance. A quite serious problem. It turned
out that when I pulled them apart the positive electrode was subject to
severe corrosion. It was simply cut off..

http://i.imgur.com/XUaQtPn.jpg
http://i.imgur.com/nMLoFbN.jpg

One of the stud mount 1N2547 rectifiers diodes was broken at off from its
studmount in the middle of the insulating ceramic material. Since this type
of rectifier was hard to find I replaced it with a modern part.

Then on I replaced other electrolytics that all measured marginal (after
all this machine is from 1967, 50 years old!). The two Mallory AC
capacitors which are the run capacitors for the paper feed system were
replaced as well. Not that they measure bad but I simply don't like oil
filled caps from the sixties. They might contain PCB oil. And I didn't find
a list that certified that Mallory RP-3301 is PCB free.

Then the PSU was fine and all voltages measured well.

On to the mechanics. The drum was working fine in both directions, but the
carriage was not moving in either direction. Checking the electronics
revealed that it tried to drive the stepper motor but nothing happened. It
was stuck.

The motor was removed and disassembled. There was a small gearbox on top of
the stepper motor and it turned out that the motor axis was completely
stuck.

http://i.imgur.com/O043J9J.jpg

By removing the last six screws it was possible to get the axis out by
knocking on the axis with a screwdriver handle. It turned out that there
was quite some rust in there. Cleaning, re-lubricating and new grease and
it worked quite well.

One note for others who repair these. Do not remove the big wheel that is
driven by the stepper motor and drives the carriage. It is not necessary
unless you plan to put some new grease in the gearbox. It is a small hell
to get the carriage cable back into position again..

After this the plotter moved nicely in all directions and then it was time
for serious testing with pens which bring us back to the topic of the
thread.

This plotter was supplied with non-pressurized pens. As far as I understand
there are pen holders for both varieties of pens as well as felt pens. Mine
are definitely non-pressurized.

http://i.imgur.com/ZquhQMT.jpg

As per Randys suggestion I put them into an ultrasonic cleaner and they
become much cleaner. Then onto filling them which turned out to be a
complex and a messy business..

>From what I understand there are different types of ink. The type of ink
that are used for reservoir pens or Harry Potter feathers which is more
liquid and then a thicker ink which is used in ballpoint pens. The former
is sold in small bottles the latter is not sold except for in ballpoint
refills.

The next step is to try to extract ink from the ballpoint refill and use a
ink refill syringe to push it into one of the cleaned pens. We'll see how
that works out.

The other option is to find new pens with the same diameter which can be
cut into the correct length and tip dimensions. Maybe even plastic ones
will work if they are stiff enough.

In parallell I am working on the interfacing part. As far as the
description in the manual interfacing is quite simple. Either negative
going or positive going pulses, at least 10V amplitude and more the 4us
long with less than 10us rise time. Source impedance less than 500 ohms.

A ULN2004 or similar together with some simple AVR microcontroller will
probably do it.

/Mattis

2017-02-23 8:27 GMT+01:00 Randy Dawson <rdawson16 at hotmail.com>:

> Suggestion: drop them in an ultrasonic cleaner with solvent...
>
>
> ________________________________
> From: cctech <cctech-bounces at classiccmp.org> on behalf of David Gesswein <
> djg at pdp8online.com>
> Sent: Saturday, January 28, 2017 10:34 AM
> To: cctech at classiccmp.org
> Subject: Re: How to refurbish plotter pens?
>
> On Sat, Jan 28, 2017 at 03:51:49PM +0100, Mattis Lind wrote:
> > I am about to get our IBM1627 (rebranded Calcomp 565) going but the pens
> in
> > the case is quite dry. What is the best method to refurbish those? What
> is
> > the best solvent to get the old ink out? What ink to refill with?
> >
> > https://drive.google.com/open?id=0B-rp4vyPPYu1ZjVRbnlyczV4czQ
> >
> That looks like the unpressurized ballpoint. I never tried to refill mine.
> Another option is making replacements. I found current ballpoint
> refills and cut them down. I used a dremmel with cutoff disk. Watch for
> splatters. I then stuck something in to remove 1/4" or so of the ink from
> the end. Otherwise it will come out in the pen holder and make a mess.
> The problem now is almost all refills use a larger diameter tip. I had to
> look around some before I found the proper size. I did grind one larger
> diameter one down by chucking it in a drill and grinding with the dremel.
>
>