Electronic calculators

The electrical part looks  like this diagram.

• Generally there is a capacitor directly over the mains connection.  It’s only purpose is to reduce electrical interference with other equipment like medium wave radio.
  This capacitor is seldom in good condition. As it may blow and spread a lot of rubish in the machine,  I always remove it.
• Next there is a capacitor which reduces sparking on the brushes/collector of the motor as well as the speed regulator.
  If it’s not in good condition you may want to replace it by a .1uF capacitor in series with a small resistor. This capacitor/resistor combination can be bought in a single housing.
  (see right picture)

The electronic calculators I bought mostly needed no repair except for replacement of rechargeable NiCad cells.
If the cells or normal batteries have been leaking,  the contacts can be cleaned with vinegar.  That generally gives satisfying results.  

NiCad cells can be replaced with modern low-leakage NiMH cells. They are available in  much larger capacity resulting in much longer charging times than originally.  However, there is a major drawback.  The old chargers don’t charge NiMh well.  (See Canon LE10)

Mechanical calculators and typewriters

Several collectors (*) helped a lot to develop the skills which enabled me to get every machine on this website in a working condition.

(*) Note: many of them present on the internet:  see Links

The very basic necessities:

• A lot of patience.
• Light to find parts which should move, but don’t.
• Good hearing to detect when something is moving where  you’re not looking.
• Some understanding how a machine is supposed to operate internally.
  That is why it helps to only gradually move to more complex machines.
• A camera to take pictures of any parts you want to temporarily loosen or  remove.

A headlight and small led light help to see what’s happening inside a machine.

Petrol mixed with a few percent of thin oil  and some small brushes help to clean the machine.

WD40 helps to loosen stuck parts.  After a successful application it’s best to remove the remaining WD40 with the above petrol mixture.

For most lubrication a reasonably thin oil is OK.
I use 5W40 motor oil for most parts.

For very small parts clock oil (Koch nr 3 or 4) seems to be fine.

For gears a multi-purpose grease is used.

Some small wrenches are used a lot: 5/16”, ¼” and 5.5mm.  Others may well be needed.

Some screwdrivers needed modification to accommodate the sometimes very narrow screw slots.