Kovac K-80D

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Calculators: Handheld(ish): Kovac K-80D (aka Tabletop mini)


		Size (approx):	135mm x 213mm x 60mm (max) (w,h,d) Weight 608g excluding batteries.
		Power:	6V DC using 4 x C size batteries. Also accepts adaptor/charger (DC 6V undefined but centre negative) through a top side socket to the far right. Regular or nickel-cadmium batteries can be used (charge when meter is red: with a quoted charge time of up to 24 hours) or alkaline rechargeable batteries (charge when meter is silver: with a quoted charge time of 16-24 hours). You can leave ordinary batteries in if the mains power is connected (but I find that hard to believe). The battery compartment has a ribbon pull to aid removal (essential) and my example has two plastic tubes to hold two C batteries each - I would be interested in confirmation that these are original, as it is quite unusual.
		Case:	Bulky calculator made from patterned dark grey and smooth light grey plastic. The top area has a black printed silver stick with the logo that sits in its own recess. there is also, in line with this, a convex battery meter which sits slightly recessed. A grey plastic display filter is sloping and slightly recessed and has white printed text for the digit numbers and symbol information. It results in a bright and flat display. The keyboard surround of brushed aluminium also sits flush in its own recessed area and has black printed text for the switch labels. The keys are large, long travel with a hollow sounding clunk. They sit slightly proud of the keyboard surround, potentially letting in a lot of dust.
		Display:	8 digit orange gas discharge (neon) display with a ninth digit for negative, input overflow and error indication
		Features:	Four standard functions with switched constant and fixed decimal modes. Semi RPN logic.
		Age:	1972, recommended retail price £59.95, Boots price (with adaptor) £39.95.
		Manufacturer:	Made in Japan, serial number 813836
		Comments:	Very solidly built calculator that really only just fits in the hand. The logic is better than expected for this era, but the lack of recovery and strange divide by zero result do let it down. A large label on the back reminds you of the calculation sequences. On my example it is very difficult to open the battery compartment. Very well built and stuffed with components as you would expect for 1972.

Components:	1 x IC: Texas Instruments TMS0105BNC 7229 (week code 29 of 1972), 28 pin DIL 0.6" width black plastic 9 x 1 digit neon gas-discharge tubes 23 x transistors 11 x diodes 19 x capacitors 67 x resistors 2 x miniature potentiometers 1 x dc-dc converter transformer 1 x miniature voltage meter
Boards:	The keyboard assembly (2927890) sits above the main board and is supported by sturdy thick plastic brackets. To lift this out remove the two screws on the corners. These are joined by 15 coloured wires.
Construction:	Remove the four screws at the rear. The front section then lifts off easily - to rest on the left as the meter wires are quite short.

Logic comments:	The (CD) key is used to clear the last entry and the (CA) to clear the whole calculator
	On power up there is no auto-reset - you have to press (CA) first as random numbers come up
	Input overflow is not suppressed, keying in a ninth digit is not entered but shows the input overflow symbol (C in the far left (ninth) digit) but you can carry on using the calculator as normal
	There is selectable constant for multiplication and division by using on/off switch in the [K] position, first register for multiplication, second for division
	Negative numbers are flagged by a minus sign in the far left (ninth) digit thereby allowing full eight digit negative numbers
	The sign change function can be used in mid number entry but is a bit erratic in my example, sometimes not allowing to you change sign of the primary register
	Overflow shows the result and "u" (or "o" if negative) in the far left (ninth) digit and is not recoverable
	Divide by zero shows zero and no indication of error and is not recoverable
	A switch is used to select fixed two/three decimal places or fully floating mode
	It suffers the divide to negative zero once bug: key in (3)(+/-)(/)(1)(0)(=)(=)(=)... etc until you get "-0", one more equals will give "0" showing the extra digit of internal precision.
	The logic is semi RPN: to do 3-6 key in (3)(+=)(6)(-=)


No so much a box as an expanded polystyrene clam shell with a paper sleeve. The sleeve measure 254mm x 183mm and is 91mm deep. Printed in halftone black and bold orange.	The manual measures 218mm x 115mm and is printed in black only with a halftone cover. The eight pages means it is quite brief, but it covers all you really need to know.

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