Olympia CD51

		Home New Stuff Author Links Guest book Web-log	Adverts Bric-a-brac Calculators Components Ephemera Events	For Sale Glossary History Hit or Miss Radios Transport	Ultra Valves Wanted Metal Puzzles Clocks

Calculators: Handheld: Olympia CD 51

	Size (approx):	80mm x 138mm x 30mm (w x h x d) Weight 160g not including batteries.
	Power:	6.0V DC using 4 x AA size batteries. It accepts an adapter (6V DC) through a socket on the top side in the middle. There is a low battery warning light - which drains the batteries even quicker!
	Case:	The case is two-piece black matt plastic which is brick shaped with a rounded sides. The top end has a ridged design whilst the bottom end carries a metallic sticker with the model number. A red display filter is slightly inset with black and white printed escutcheon and letters batt. and K. The display image is a little dull on my example with good angle of view. Just below the display a metallic sticker, printed black and red with the Olympia branding, sits in its own recess. A small upper recess contains the two upper switches. The nearly flush keys are very short travel positive click type and work reasonably well.
	Display:	8 digit red LED (multi-dot flat type) with a ninth digit for negative and error indication. There are two separate single red LED below the digits, one for constant indication, one for low battery warning.
	Features:	Standard four functions with change sign, switched decimal point and switched constant. RPN logic.
	Age:	c1972-3
	Manufacturer:	Olympia Pocket Calculator, Olympia International, serial number 43130164.
	Comments:	A very solid feeling calculator with nice LED display (though a little dim). Archaic RPN logic and single LED indicators have now long gone. I’m not sure why they bothered with the constant indicator as you can see it is on from the switch. This is very similar in design to the Hanimex BCM 817. The original case is soft black plastic with a top flap that tucks in a band on the front. The band has Olympia embossed in large letters.

Components:	1 x cpu: Texas TMS0103NC B7250 (week 50 of 1972), 28 pin DIL, 0.6" width 2 x IC: Texas SN75491N 7239, 14 pin DIL, 0.3" width 2 x IC: Unknown, 14 pin DIL 0.3" width 3 x 3 digit LED flat display units 2 x individual red LEDs 8 x transistors 2 x diodes 6 x capacitors 17 x resistors 1 variable resistor 1 x transformer block
Boards:	The main cpu board sits on top of the keyboard assembly (IKs114 45218 1st ISS) fixed by two screws. A bunch of thirteen wires connects the the keyboard which is fixed to the front via 4 screws.
Construction:	There is a screw under the metallic plate on the bottom end of the calculator. If you wish to damage the plate by removal then after this the case separates fairly easily with the back lifting off its side lugs.

Logic comments:	The (CE) key is used to cancel an entry whilst the (C) key clears the whole calculator
	Input overflow is not suppressed; inputting a ninth digit causes an error - but you can still carry on calculating or you can cancel the entry using (CE)
	Negative numbers are shown with a "-” in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	There is switched constant [K] on multiply and divide by using the On/Off/K switch. This is normally OK as the (+=) key usually acts like a constant – but not in this case. To remind you that constant is switched on an individual red LED lights.
	The change sign function can be used in mid number entry
	Divide by zero shows “o” in the far left (ninth) digit and is not recoverable
	Overflow shows the result and “o” in the far left (ninth) digit and is not recoverable.
	When the batteries are low an individual red LED lights
	You can select Floating [F] decimal point, fixed [4] or [2] digit by use of an upper switch
	The logic is Reverse Polish Notation so to work out 5-2 you key in (5)(+=)(3)(-=) which shows “2”.

	The scan on the left shows the small, very dense cpu board. Two additional ICs (as well as the transformer) are underneath the black cardboard display surround. It is clearly of an early 1970 era from the large transistor and IC count. You can also see the display consisting of three units with two additional LEDs mounted underneath,