Genesonic 3683

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Calculators: Handheld: Genesonic 3683


		Size (approx):	77mm x 152mm x 9-20mm (w,h,d) Weight 98g excluding batteries
		Power:	9.0V DC, 1 x PP3 size battery. It accepts an adapter (undefined, 9V DC centre negative) on the top edge to the far right
		Case:	Wedge shaped calculator made form a two piece matt black plastic case narrowing to quite a thin point. The red plastic display filter is flat , flush and tilted to give a bright but limited angle of view. Below this is a metal panel with black lines and text for the brand name and model number. The keys are large (scrabble-tile like) with a very short travel and loud positive click. On my example they suffer moderate bounce problems. The on/off switch label is embossed on the matt black plastic keyboard surround.
		Display:	8 digit red LED with bubble lens and no ninth digit
		Features:	Standard four function with percentages
		Age:	1976
		Manufacturer:	No details, made in Hong Kong, serial number H182081 on a sticker inside the battery compartment.
		Comments:	Slim calculator with lovely , if unreliable, keys. Very similar to German Privileg models like the Privileg 85. The logic appears sound but let down by a negative zero bug and seven digit negative numbers. The overflow state is odd as it throws away the least significant eight digits of the answer.

Components:	1 x cpu; General Instruments C-683 7620 (week 20 of 1976), 28 pin DIL, 0.6" width black plastic 1 x IC: National Semiconductor NS DS8865N 606 (week 6 of 1976), 18 pin DIL, 0.3" width black plastic (likely display driver) 1 x 8 digit red LED module with individual bubble lens 0 x transistors 1 x capacitor 9 x resistors
Boards:	The main board doubles as the keyboard assembly and is attached to the front with five screws.
Construction:	Quite difficult to open as it is held together by internal lugs only. I found the best way was to pop the top edge, then work down the sides with a wooden lollipop-stick - pressing in the front piece sides. Be very careful as it is easy to damage you calculator. The rear will eventually hinge off from the bottom.

Logic comments:	The (C/CE) is used to clear an input number whilst a second press will completely reset the calculator
	Overflow on the input of a number is suppressed: keying a ninth digit is ignored
	There is automatic constant on all four functions
	The negative sign is shown in the immediate left hand digit but as there is no ninth digit to travel into you are limited to seven digit negative numbers
	Overflow shows the result shifted by eight digits and all decimal points alight and is recoverable using (C/CE). This is a bit annoying as you can end up with the answer being a single digit having lost the other eight.
	A divide by zero error shows ".......0." and is not recoverable.
	It suffers the divide to negative zero bug: key in (1)(-)(=)(=)(/)(1)(0)(=)(=)(=) etc until you get "-0". The last real number to be displayed drops the leading zero to show as "-.0000001"

This image shows the calculator with the back removed. You can see the nearly full length single board that doubles as the keyboard assembly and main cpu board.

It is surprising to see such a late LED calculator with secondary IC driver for the display: obviously the GI IC could not drive the high current directly.

Compare it to the inside of the Privileg 85.