How to refurbish plotter pens? (roller-ball pens)

[Stefan Skoglund]

tor 2017-04-06 klockan 19:59 +0200 skrev Mattis Lind via cctalk: 
> 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.
> 

Ballograf in Mölndal is nowadays the only roller-ball pen producer in
sweden (Scandinavia too?) Maybe they would be amenable to sending a
bottle of ink (they are world-famous for producings roller-ball pens
with
archive-longevity inks.)

> 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