Some handy tips I have learned whilst restoring these machines
> Most problems you will encounter is the old oil has turned to a stiff, sticky mess and glued moving parts together.
A electronics heat controlled hot air gun is very good for softening it up so you can get it moving enough to work
some new oil in to it. In extreme cases I have found heating it by resting a soldering iron on to it has worked
> Solder is very handy for repairing broken parts (I find an electronics soldering iron and solder works fine),
with small parts you can actually form the molten solder in to shapes and it is a very handy way to build up worn
surfaces. I have even in one case managed to replace a broken gear wheel tooth in this way which worked
surprisingly well. It will of course not be as strong as the original metal but it works and also is very easy to
remove at a later date if required so doesn't cause any permanent damage to the machine.
> Water slide decal printer paper is very handy for replacing missing text/labeling etc. and also very handy for
putting the text on replacement key caps. You simply print your required text/image (if printed on an inkjet you
need to then seal it with a spray laquer), cut it out, put in some water to soften the glue and slide it in to place.
This is very good for putting the text on replacement key tops.
> Patents are a good place to find information on how the calculators work etc, you can search them at
espacenet (thanks Martin Cummins for suggesting
> With the add-lister type machines such as the Olivetti and Citizen there is a bar which a carriage slides along as
the numeric keys are pressed, I have found oiling this a very important first step as this sticking can be the cause
of a lot of issues.
> With cracked/broken plastic cases I find sinking some fine wire stainless steel mesh in to the plastic across the break
with a soldering iron makes a good/strong repair. Fine adjustment can be made by heating the area with a hot air gun.
To replace missing plastic putting some baking powder on it, dripping superglue on to this then building up more layers
> If you need to replace a drive belt search eBay for 'Round Polyurethane Conveyor Drive Belt PU Green Rough Surface