Casio FX-19

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Calculators: Handheld: Casio FX-19


		Size (approx):	89mm x 148mm x 28mm (max) (w,h,d) Weight 180g excluding batteries.
		Power:	6.0V DC, 4 x AA size batteries, 0.35W. Also accepts adapter/charger (AD-4145) through a top side socket on the left.
		Case:	Smooth plastic white base and black front. There is a large inset brushed aluminium panel around the keyboard which is printed with black and tan text. A neutral and slightly tilted plastic display filter is topped with a black printed silver sticker in its own recess. This holds the brand name and model number. The usual squishy but positive Casio keys have their own plastic escutcheons.
		Display:	10 digit blue VFD which is used as an 8 digit (plus ninth for negative) or 6+2 scientific mode (or 5+2 negative scientific mode). The tenth digit is never used.
		Features:	Four standard functions, fractions, reciprocal, square root, logs, powers, change sign, sexagesimal input, trigs, pi, statistical and four function memory. Switched Degree, Radian, Gradian and Standard Deviation modes.
		Age:	1976
		Manufacturer:	Casio Computer Co. Ltd. Made in Japan, serial number 4255420 on a sticker in the battery compartment.
		Comments:	Well built but limited scientific calculator that is let down by the restricted five digit negative mantissa, eight digits of precision and lack of error recovery. Fractions are great but they missed the display of sexagesimal numbers. Looks a bit odd with all those multi-function keys - but a big gap with one missing. Original case is soft black plastic with two top flap with popper closing. It has Casio embossed on the front and Made in Japan on the back.

Components:	1 x cpu: Hitachi HD36130 6E13 (week 13 of 1976), 28 pin DIL, 0.6" width black plastic 1 x 10 digit VFD display, round faced single tube; LD8150/E6548 2 x transistors 11 x diodes 12 x capacitors 5 x resistors 1 x transformer
Boards:	The Keyboard assembly (D8K-E4A GCMK-19EHB) is fixed to the front by nine screws and attached to the cpu board (D8K-1A) via 15 copper wires in two clusters. A small piggy-back board houses the power driving circuit. The cpu board has a square hole cut-out for the glass display vacuum pinch, but is not needed in my example.
Construction:	Remove the screw from the back and the second screw from within the battery compartment. You can then remove the front with a blunt thin instrument pocked through the latter hole. Warning - there are two lugs on the top of the front that have to be carefully levered out - high possibility of snapping them so take great care. Swing out the front to the right hand side.

Logic comments:	The Clear key (C) is used to clear an input number, the all-clear (AC) to completely reset the calculator.
	Overflow on the input of a number is suppressed, keying in an ninth digit is ignored
	The constant function is invoked for multiply and divide by a double press of the operator, squares cab be performed using (n)(X)(=)
	There is no indication of memory use - you have to remember it.
	The negative sign is to the immediate left of a number travelling into the ninth digit thereby allowing full eight digit negative numbers. In scientific mode you can display only a five digit mantissa as the tenth digit is not used. The tenth digit is never used and you cannot add an exponent to a six digit negative number.
	On overflow the display just shows "E" in the far right (first) digit and is not recoverable
	On divide by zero the display just shows "E" in the far right (first) digit and is not recoverable
	Negative square roots are not allowed and result in an error as above
	Standard scientific mode is six digits plus two exponent with one intervening extra digit for negative indication of the exponent
	The change sign function can be used in mid number entry but not before
	Scientific functions are limited to eight digits of precision only
	Degrees (or hours), minutes and seconds can be displayed and manipulated by entering (4)(^o ' ")(3)(^o ' ")(2)(^o ' ") which will display the decimal notation "4.050555555". There is no conversion to a sexagesimal display.
	Fractions can be manipulated and displayed using the (a b/c) key with a small reverse "L" separator
	Power raising shows the intermediate step of using a log so that (2)(X^y) shows "0.6931471" then (8)(=) gives "256".
	A switch allows you to change the trigonometric functions between Radians, Degrees and Gradians.
	No major bugs found.