Decimo Vatman Mini S

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Calculators: Handheld: Decimo Vatman Mini S

		Size (approx):	72mm(max) x 123mm x 20mm(max) (w,h,d) Weight 104g excluding batteries
		Power:	3V DC, 2 x AA size batteries. It accepts an adapter (3V 100ma 3.5mm plug centre positive) through a socket on the bottom side on the far right.
		Case:	Made from a two-piece gloss finish brown plastic case with rounded edges and corners. There is an oversized green display filter that gives a bright display. It contains a small metal label that is printed black with the model name and sits in its own recess. A brushed aluminium keyboard surround has the power switch and higher function labels printed in black. The keys are small and squishy but work well.
		Display:	8 digit green VFD, with a ninth digit for negative, memory and error indication.
		Features:	Standard four functions with percentages, change sign, pi, square root, square, reciprocal, and four function memory.
		Age:	early 1976
		Manufacturer:	Undefined manufacturer, made in Japan, serial No. 8475753
		Comments:	Compact calculator that is nice to hold with its smoothed edges but I'm not sure about brown. The "S" suffix in the name refers the the "Scientific" functions. The logic is sound with almost good, if unconventional, but let down by poor memory overflow and negative square roots. Similar designs can be seen in Same Calculator.

Components:	1 x cpu: NEC µPD946C R5Z876, 28 pin DIL 0.6" wide black plastic 1 x 9 digit VFD with round face 1 x transistor 4 x diodes 7 x capacitors 7 x resistors 2 x resistor arrays 1 x transformer: Z800
Boards:	The keyboard assembly (GICO 51.1.29 - which is the 29th January 1976) (171-2Y-811R) floats on top of the main cpu board and is held together with ten screws. It attached to the main cpu board via a 15-way ribbon cable.
Construction:	Very difficult to lever off the front as the lugs are on the rear section and this is very rigid. Front panel eventually lifts off. I would not recommend trying for fear of damaging the calculator.

Logic comments:	(CE) is used to cancel the last number entered and (C) to clear the whole calculator.
	There is automatic constant on all four functions
	Input overflow is not suppressed, keying in a ninth digit results in an overflow which can be recovered by dividing by ten
	Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight-digit negative numbers
	Divide by zero shows zero and "C” in the far left (ninth) digit and is not recoverable
	Overflow shows the result with "C" (or “E” if negative) in the left most (ninth) digit and is recoverable by dividing by multiples of ten
	The change sign can be used in mid-number entry but not before
	Memory store is indicated by the decimal point of the far left (ninth) digit
	Overflow in memory is not indicated but when recalled the error state is flagged and the result is held in memory, shifted and recoverable by dividing by multiples of ten
	Negative square roots are allowed and result in a negative number
	Higher functions are access by a two key sequence to reduce the number of keys required. to work out the reciprocal of 10 key in (1)(0)(F)(÷)
	There is no indication of 'Function' selection, you have to remember it
	No bugs found

This scan of the inside shows the rather messy layout of components. Note that the VFD tube is mounted midway to the board to reduce the overall thickness.

At the bottom you can see the ribbon connector to the keyboard assembly.

Compare the inside of all three in this series.