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Calculators: Handheld: Olympia CD 81

Size (approx):

100mm x 165mm x 40mm (w,h,d)
Weight 492g including sealed batteries

Power: 6V DC using a sealed rechargeable battery pack which is integral with the battery compartment cover.  It accepts an adaptor/charger (DC 6V 0.7W, centre positive) through a socket on the right side at the far bottom.  This socket is actually contained in the battery pack.  There may have been an option to replace this with a disposable battery holder.  There is a battery low indicator.  Handy hint: if your sample, like mine, has a duff battery unit and does not operate of an adaptor, all is not lost.  With the battery unit removed join the positive lead to the right hand side lug (looking from the rear) to power it up.
Case: Large and very unusual design; the keyboard area and display push forward with every corner and edge heavily rounded.  The whole case is made from white and light grey thick gloss plastic which is obviously built to last.  The neutral, oversized display filter is slightly tilted and gives a clean bright image. Underneath the filter is printed text for the digit numbers and a reminder of the battery indicator. The Olympia logo in red and black is printed in the lower well.  The on/off switch has an aluminium panel surround which sits in  its own raised recess.  The keys are long travel, squishy and work OK.  A long white plastic carry strap fixes to the left hand side.
Display: 8 digit blue VFD with a ninth symbol cluster for negative, error and low battery indicators 
Features: Standard four functions with switched memory accumulator and one-function memory
Age: 1973
Manufacturer: Olympia Werke Ag., Wilhelmshaven / Western Germany, made in Japan.  Serial number 0904980, also 0701896.
Comments: Very high quality calculator from the early 1970s.  This appears to be exactly the same as the Panasonic 855 made by Matsushita.  Very unusual shape that looks organic with its prominent curves and quirky style - a must for everyone's collection.  Logic is OK but the lack of recovery is to be expected from such an early model.  The original case is a lovely light blue plastic with white piping on the edges.  It is a top and half-right side zipping case with Olympia printed in white on the front.  There is a gap in the zip to allow the carry strap to poke though.

Components: 1 x cpu; Texas TMS0131NC 7321 (week 21 of 1973), 28 pin DIL, 0.6" width
1 x unidentified component labelled IC 6291 737 in a 11 pin SIL package
8 x 1 digit VFD tubes with 1 x symbol cluster tube
20 x transistors
8 x diodes
6 x capacitors
31 x resistors
5 x resistor arrays
1 x transformer; CT-860 TDK
1 x fuse
Boards: The keyboard assembly (Hitachi H MCL-44 CF74104A) is attached to the front with 8 screws. It is unusual as each key has its own magnet and reed relay that switches in the proximity of a magnet. The main cpu board connects to this with a 20-way connector.  Built at no expense for easy servicing.  The display, likewise sits on the main board with its own connector.
Construction: There is a screw under the grey label just above the battery compartment.  This, however, does not help a lot.  You need to push the white front section in whilst trying to pop the lugs from any side.  This is very difficult as the case is so thick that there is very little give on the sides.  If in doubt, do not bother as you may damage your example.  Eventually the rear will lift off.

Logic comments: (C) clears the whole calculator, there being no cancel entry function that I can find
Input overflow is suppressed, inputting a ninth digit is ignored
There is automatic constant on all four functions
Negative numbers are shown by a minus sign in the far left symbol cluster thereby allowing full eight digit negative numbers
Divide by zero shows zero and a lower "E" in the far left symbol cluster and is not recoverable
Overflow shows the result and a lower "E" in the far left symbol cluster and is not recoverable
Memory store is not indicated except by the switch revealing the letter "M"
Memory is switched accumulated, when on, every (=) keystroke will add to the memory.  Use (RM) to recall the memory.
The only way to clear the memory is (0)(-)(RM)(=) or to overflow it

The top image shows both the display unit with the nine individual tubes mounted in a metal holder.

The lower image shows the main cpu board which is crammed with components.  The two green sockets connect to the keyboard and display unit - no expense spared for easy servicing.