Kovac Pocket Memory P-81

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Calculators: Handheld: Kovac Pocket Memory (aka P-81)


		Size (approx):	77mm x 138mm x 20mm (w,h,d) Weight 112g excluding batteries.
		Power:	3V DC using 2 x AA size batteries. Also accepts adapter/charger (3V undefined) through a top side socket on the far left. The on/off switch is located on the left hand side, in line with the lower edge of the upper label.
		Case:	Slim but solid feeling calculator with a two piece case made of light grey (smooth) and black (matt) plastic. The upper sections has a black printed metallic sticker that sits in its own recess. The slightly raised but flat green display filter gives a clean bright display. The keyboard is surrounded by a brushed aluminium panel that wraps round the vertical edges. They keys are Casio-like, soft and squishy with individual plastic escutcheons and work very well.
		Display:	8 digit green VFD with a ninth digit for negative, memory and error indicators.
		Features:	Four function with percentage, change sign, square root and three function memory
		Age:	1975
		Manufacturer:	Kovac Corporation, made in Japan. Serial number 312499 on a sticker inside the battery compartment.
		Comments:	Solid enough calculator which reminds one of a Casio. The logic is OK but let down by lack of recovery and the "negative zero" and "fixed decimal" bugs. Original case is stiff black plastic with top tuck in flap.

Components:	1 x cpu: Sharp L12003 5I1 025 (1975) 28 pin DIL , 0.6"width 1 x 9 digit VFD: single glass tube, flat faced; Futaba 9-ST-10 5J (1975) 2 x transistors 3 x diodes 7 x capacitors 6 x resistors 2 x resistor arrays 1 x transformer: 151 002
Boards:	The main cpu board (111003) sits loosely on top of the keyboard assembly and is joined by a 12-way ribbon cable. There is a mini-board (holding the adapter socket, switch and a resistor) which is held in place by a plastic rivet.
Construction:	Remove the small screw from within the battery compartment. Carefully lever off the right hand side and you can pop the lugs gently. The rear section will then hinge off from the on/off switch side.

Logic comments:	The (C) key is used once to clear the last entry whilst a second press clears the whole calculator; so it is really a (CE/C) key
	Overflow on the input of a number is suppressed, typing in a ninth digit is ignored
	There is automatic constant on multiply and divide only
	Negative numbers are flagged by a minus sign in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	The change sign function can be used in mid number entry
	Divide by zero shows zero and "C" in the far left (ninth) digit and is not recoverable
	Overflow shows the result and "C" (or "E" if negative) in the far left (ninth) digit and is not recoverable
	Negative square roots are not allowed and result in zero with a "C" in the far left (ninth) digit and is not recoverable
	There is the "negative zero" bug; try (1)(-)(2)(=) to give "-1" then (+)(1)(=) will give you "-0"
	There is a fixed decimal bug, try; (0)(.)(0)(0)(0)(+)(1)(=) gives "1.000" which remains with three fixed decimals until you use multiply or divide or more are needed.
	Memory store is indicated by the decimal point of the far left (ninth) digit
	Memory cancel is performed by pressing (MR) twice; so it really is a (MR/MC) key