Classification: / Procedures,
Info: Thanks to DUDEK Emil (the author of this procedure) to make the museum publish his notes.

Why Bother?
If you've got this far then you are probably already or about to become a calculator collector.
So why bother to open them up? Well to start with how about watching the development of assembly techniques,
components and their reduction in count, subtle differences in the display technology and sheer inventiveness of
the people designing everything into such a small package.

Not enough for you?
You can also track the development of the ICs, allegiances between manufacturers and IC makers and branding by other companies.
I have seen some collectors go as far as reverse engineering the circuit and even the IC which I will let them get on with.
I have some apparently identical models that are radically different inside due to revision,
and some different calculators that have exactly the same bits and pieces inside - shout copycat!

Warning
However attractive as it might appear, heed the following warning:
your collection is a part of historical research. Many of these calculators were thrown away in our "disposable-technology" world.
You may have the last surviving example of that particular model!
I know that the last thing I want to see on my examples is a score of screwdriver marks down the left hand seam of the case
coupled with cracking around the lugs - be careful - and if in any doubt - don't do it.
If you must have a look in a calculator and you want to hone your skills then buy some shabby "spare part" examples and
learn from experience.

Basic guidelines - One simple rule: the early the model, the easier to open.
Late 60s and early 70s
Consisting mostly of desktops and early portable calculators these were built as major electronic apparatus.
There reliability was doubtful so attention was paid in the design to ease of servicing.
The sale value was very high so no expense need be spared in case design; screws and brackets were often used to hold the whole thing together.
Calculators from this period can be easily opened by a couple of screws with little risk of damage. Warning: be careful to note the layout of wires and boards so that you can assemble it correctly.

Mid 70s
Mostly portable and pocket calculators still achieving a high revenue.
The smaller cases were often held together with one or two screws and a few "lugs" of plastic that latched into the opposing side.
Warning: some screws may be hidden under model labels which are impossible to peel off and replace without damaging.
Corners were beginning to be cut by letting the main board sit loose in the case.
Some from this period can be quite tricky to open so the risk of damage is greater.
Warning: lugs can very easily be broken so do not use excessive force.

Late 70s
Mostly pocket calculators that were built as cheaply as possible due to the aggressive market pricing.
They may never have been designed to be opened and repaired at all.
Most do not have screws and are held together by internal lugs only. These are very difficult to get open without doing at least minor damage to the edging.
Sometimes there are "coin slots" that help to lever the sides apart.
Occasionally there are access points in the battery compartment to help apply pressure to the front (as in some ROCKWELL models).
Warning: the plastic cases are very soft, do not use a metal screwdriver, use something softer like a wooden lollypop stick.
Often, squeezing in the sides (of either the front or rear part of the case) will make the lugs pop easily.
If you see no obvious give then don't push it! Some (like the Sinclair Oxford series) appear to be impossible;
switches and adapter sockets getting in the way just too much.

Early 80s
By now, pocket calculators were never designed to be opened for servicing and occasionally might even be permanently sealed.
To be honest there is not a lot to gain from opening these as they just consist of an IC and a display.
The ICs were not even packaged; surface mounting and covering with resins being cheaper assembly methods.


Earthing
Most collectable calculators were made with MOS or CMOS ICs and are very sensitive to static discharge.
You may be familiar with the affect of static from getting shocks on dry days when touching metal items.
Warning: most static discharges are not this large and can be so small that you didn't even notice anything.
Even a very small static discharge can completely destroy a calculator IC. Make sure that you are earthed to prevent this problem.
Connect yourself to an earthed source such as a radiator or metal water pipe with a connection that touches bare metal.
Better still get a professional anti-static wrist band and mat for your workbench which will have wires to connect to Earthing points.
Warning: do not use your household earth from your power sockets this could kill you!

Frustration Rewarded
Finally, if you can solve most of the problems, the satisfaction from cleanly opening a calculator and the knowledge you gain from examining the insides
will add a new dimension to your hobby.