Casio FX-39

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Calculators: Handheld: Casio FX-39


		Size (approx):	84mm x 152mm x 22.5mm (max) (w,h,d) Weight 146g excluding batteries.
		Power:	3.0V DC, 2 x AA size batteries, 0.75W. Also accepts adapter/charger (AD-4145) through a top side socket on the left. Two alkaline/manganese batteries give about 22/8.5 hours continuous operation, a fully charge Ni-Cd pack (NP-2M) about 9 hours.
		Case:	Smooth plastic white base and black top. Inset brushed aluminium panels around keyboard and above display. Neutral and slightly tilted plastic display filter gives a clean image. Logo, brand and key functions are printed in black, blue and orange. On off switch located perfectly on left side about 2cm from the top. Units switch on the right hand side front corner is also easy to use. Subtle black and grey keys with only two highlighted in orange. Squishy but positive keys.
		Display:	8 digit blue VFD with a ninth digit for negative indicators.
		Features:	Four standard functions, reciprocal, factorial, square root, squares, logs, powers, nth root, change sign, sexagesimal display, trigs, fractions, register exchange, 6-level parenthesis, pi statistical and four function memory. Switched Degree, Radian, Gradian modes. 6+2 scientific display mode.
		Age:	1978
		Manufacturer:	Casio Computer Co. Ltd. Made in Japan. Serial number 4469155 on a sticker in the battery compartment.
		Comments:	Fabulous quality calculator from a famous range. As they got it so right, this layout remained for years - well into LCD calculators. Displays fractions with a reversed "L" symbol and angle separator with "⁰". Sound logic - but annoying limited mantissa and error recovery. Supplied originally with an open topped leatherette case with Casio logo embossed on front.

Components:	1 x cpu: Hitachi HD38111A6130 8C23 (March 1978), 28 pin DIL, 0.6" width 1 x 9 digit VFD display, round faced single tube; NEC FIP9D5 No. 7M 3 x transistors 12 x diodes 9 x capacitors 5 x resistors 1 x transformer: TDK TC-15 2C1
Boards:	The Keyboard assembly is fixed to the front by five screws and attached to the cpu board (G8P-1B) via 19 copper wires in two bunches.
Construction:	Remove the single screw for the battery compartment. Still quite difficult to open. Open the lug visible to the left of the compartment by gently pushing in the brown plastic front. There are two lugs on each side that are very difficult to pop as the plastic sides are so stiff. Warning - very likely to damage it so be very careful. Hinge off the back to the right.

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, typing in a ninth digit is ignored
	The constant function is invoked for all four functions by a double press of the operator.
	There is no indication of memory use - you have to remember it.
	The negative sign is to the immediate left of a number, it can push to the ninth digit to allow 8-digit negative numbers
	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 two extra digits for negative indication
	The change sign function can be used in mid number entry but not before
	Fractions can be displayed and manipulated by entering (2)(a ^b/c)(1)(a ^b/c)(2)(a ^b/c) which will show 2½ as "2 û 1 û 2." Use (INV)(a ^b/c) to convert to decimal which is not reversible.
	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 "4.050555". Use (INV)(^o ' ") to convert the display to "4^o 3^o 2."
	Internal precision is up to eleven digits, through pi is held to ten and trigs to nine. To see the extra digits try (9)(1/X) to give "0.1111111" then (-)(0.1111111)(=) will give "1.11 x 10 ^-8)
	No major bugs found.

One colour 40pp booklet in English and Spanish. 81mm high by 119mm wide. Very detailed with lots of examples of scientific calculations

Printed in Japan