Casio Personal Mini CM-607

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Calculators: Handheld: Casio Personal-mini (aka CM-607)

Size (actual):	142.7mm x 69.0mm x 25.0mm (w,h,d) Weight 130g excluding batteries
Power:	3V DC, 2 x AA size batteries. It accepts an adaptor (AD-2S, 0.2W) through a socket on the top side just to the right of the display. Battery lifetime is quoted as 10 hours (standard Manganese) or 22 hours (alkaline). If you use a universal adaptor switch it to centre negative.
Case:	Horizontal format two-piece case in aqua-blue and white matt plastic. Inset display escutcheon in black plastic. A further inset panel has printed model number and reversed out Casio name. There are two highlighted ridges around the display area that are printed white. Large, long travel hollow sounding keys work well. Neutral display filter gives a rather dull image with odd "small zero" notation (see below).
Display:	6 digit blue VFD, with no seventh digit for additional display. A shift-display key helps out.
Features:	4 function calculator with display shift.
Age:	estimate 1975
Manufacturer:	Casio Computer Company Ltd. Made in Japan, serial No. 5148555 (on battery cover) and 4731281 (inside battery compartment). This may be a spare battery cover on my sample. Oddly enough, the information panel on the back is upside down.
Comments:	One of a range of early, solidly built horizontal calculators by Casio. The Personal-mini name was used for another similar one, but this model does have a "CM" number to identify it. Quirky logic and annoying display (often to save money) is made up by the wonderful divide by zero bug!

Components:	1 x cpu: NEC µPD178C R55566 28 pin DIL 1 x 6 digit VFD display single glass tube 2 x transistors 5 x diodes 13 x capacitors 2 x SIL resistor arrays 9 x resistors 1 x transformer: TDK CD-14202 6C
Boards:	The keyboard board (ref 6V-E4B) is fixed to the front via five screws and to the main cpu board (ref 6V-1A) by 9 stiff wires. The latter is L-shaped to avoid the battery compartment.
Construction:	Remove the single screw in the battery compartment and very gently squeeze in the white section to release the lugs one by one. Not for the faint hearted - so do not attempt if you want to keep the calculator pristine.

Logic comments:	The (C) button is used to clear last entry of a number and the (AC) to clear the whole calculator.
	Overflow on number input is suppressed, typing in a seven digit number ignores the seventh digit.
	An overflow error is flagged with the answer displayed and viewable using the shift key (>) and is not recoverable
	Negative numbers are shown by a "-" in the sixth (left) digit and during display shift in the first (right) digit. This is annoying for six digit negative numbers as you do not see the minus sign on the un-shifted display
	It does not have full 12 digit precision: the answer to 22/7 is "3.14285" (>) "000000"
	Divide by zero results in "000000" being displayed - but use the shift key to see the clock running! It is not recoverable.
	It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1" now (+)(1)(=) to give "-0"
	There is automatic constant on all functions

Note the unusual way that zero is represented - by only using the lower half of the digit.


The box on the left measures 83mm x 170mm and is 38mm deep. It is a two colour tuck end carton with no room for anything but the calculator. Printed in Japan.		The manual on the right measures 100mm x 75mm and is printed in one colour black. Halftone image suffices for the front. It has 12 fan-fold pages with basic but good instructions.