Decimo Vatman Mini M

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Calculators: Handheld: Decimo Vatman Mini M

		Size (approx):	72mm(max) x 123mm x 20mm(max) (w,h,d) Weight 100g 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 label 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, and four function memory.
		Age:	early 1976
		Manufacturer:	Undefined manufacturer, made in Japan, serial No. 8596781
		Comments:	Compact calculator that is nice to hold with its smoothed edges but I'm not sure about brown. The "M" suffix in the name refers the the memory function. The logic is sound but the recovery with (C) is odd (rather than (CE)) and it suffers from the "negative zero bug. The original case is soft black plastic with open top and half-moon cut-outs on the front and rear. Similar designs can be seen in Same Calculator.

Components:	1 x cpu: Matsushita M58618-81P 564N, 28 pin DIL 0.6" wide 1 x 9 digit VFD with round face 1 x transistor 6 x diodes 6 x capacitors 7 x resistors 2 x resistor arrays 1 x transformer: Z800
Boards:	The keyboard assembly (171-3Y-801M) floats on top of the main cpu board and is held together with ten screws. It attached to the main cpu board via a 13-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 suppressed, keying in a ninth digit is ignored
	Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight-digit negative numbers
	Divide by zero shows "C” in the far left (ninth) digit and is recoverable using (C)
	Overflow shows the result with "C" (or “E” if negative) in the left most (ninth) digit and is recoverable using (C)
	The change sign can be used in mid-number entry
	Memory store is indicated by the decimal point of the far left (ninth) digit
	This calculator suffers from the negative zero bug; try (1)(-)(2)(=) to give "-1" the (+)(1)(=) to give "-0"

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.