Casio Memory-8F H-812

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Calculators: Handheld: Casio Memory-8F (aka H-812)


		Size (approx):	76mm x 138mm x 22mm (max) (w,h,d) Weight 128g including batteries.
		Power:	3.0V DC, 2xAA size, 0.2W. Also accepts adapter (AD-2S) through a socket on the top side to the far left. The on/off switch is on the left hand side in line with the word Casio.
		Case:	Three piece gloss plastic case with base in black, top in white and a third front piece in matt black. The neutral, slightly tilted and inset display filter gives a clear image. A small panel at the top has white and blue printed text for the make and model number. A similar panel surrounds the keyboard with silver text for the switch labels. The keys are the typical squishy Casio ones that work rather well.
		Display:	8 digit blue VFD with no ninth digit.
		Features:	Standard four functions with percentages, square root and three function memory. Switched floating or two digit decimal mode.
		Age:	1976
		Manufacturer:	Casio Computer Co. Ltd. Made in Japan. Serial number 6428864 on a sticker inside the battery compartment.
		Comments:	Quite large sturdy Casio that has layout of the Memory-8A. Complex case design with gentle curves and rounded corners make this in the hand well. The logic is poor with limited negative numbers, negative zero bug, no recovery and negative square roots - try again Casio! There were at least two versions of this calculator, the other using display type LD8120B on main board version C8T-1A.

Components:	1 x cpu: NEC µPD977C R63129, 28 pin DIL, 0.6" width black plastic 1 x 8 digit VFD; single tube round face, E6535A 6D (date code April 1976) 2 x transistors (one dated coded 6B4, February 1976) 5 x diodes 8 x capacitors 4 x resistors 2 x resistor arrays 1 x transformer; 4D CD1010 TDK (which would tend to imply February of 1974 - so perhaps it was old stock)
Boards:	Main board (C8U-1A) is connected by 12 copper wires to the (and sits on top of the) keyboard assembly (C8T-E4A. The latter is secured to the front by 6 screws. There is a small piggy back board module with the transformer and associated components.
Construction:	Remove the single screw from the inside of the battery compartment. Then try to pop the side lugs by pushing in the white front section. Quite difficult to do without causing damage so be very careful. The back will eventually lift off.

Logic comments:	The (C) button is used to clear last entry of a number and (AC) to clear the whole calculator.
	Overflow on number input is suppressed, keying in a ninth digit is ignored
	There is selectable automatic constant on all multiply and divide only by double hitting the operator; i.e. (3)(X)(X)(=) gives "9".
	An overflow error is flagged with an "E" in the first (right most) digit, negative or positive and is not recoverable.
	Divide by zero shows an "E" which is not recoverable.
	A round off switch and fixed two-decimal point notation is available.
	Square roots of negative numbers are allowed and result in a negative number
	Square roots are limited to seven digit precision
	Negative numbers are flagged by a "-" sign in the immediate left digit, limiting you to seven digit negative numbers. If you key in (-)(1)(2)...(8)(=), this will result in an error.
	There is no indication of memory store - you have to remember it, and (AC) clears the memory
	Memory overflow clears the memory as you have to use (AC) to recover
	It suffers the negative zero bug; key in (0)(-)(1)(=) to give "-1" then (+)(1)(=) results in "-0"