Decimo Vatman Mini

		Home New Stuff Author Links Guest book Web-log	Adverts Bric-a-brac Calculators Components Ephemera Events	For Sale Glossary History Hit or Miss Radios Transport	Ultra Valves Wanted Metal Puzzles Caravan

Calculators: Handheld: Decimo Vatman Mini

		Size (approx):	72mm(max) x 123mm x 20mm(max) (w,h,d) Weight 102g excluding batteries
		Power:	3V DC, 2 x AA size batteries. It accepts an adapter (3V 100ma, 0.2W 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 sits flat and flush and 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 and error indication.
		Features:	Standard four functions with percentages, and square root.
		Age:	early 1976
		Manufacturer:	Undefined manufacturer, made in Japan, serial No. 8317867
		Comments:	Compact calculator that is nice to hold with its smoothed edges but I'm not sure about brown. The logic is sound but poor error recovery and negative square root lets it down. 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: NEC µPD940C R59076, 28 pin DIL, 0.6" width 1 x 9 digit VFD unit: single tube round front: Itron DP9544 Japan 1 x transistor 5 x diodes 7 x capacitors 8 x resistors 2 x resistor arrays 1 x transformer
Boards:	The keyboard assembly (GICO 50?-10-13) (date code 13 Oct 1975) sits loose on top of the main cpu board and is connected via 12 strong wires. The whole assembly sits loose in the calculator.
Construction:	It is very difficult to prize apart the case that is held together by internal lugs only. You need to push the rear section sides in to pop the lugs but damage is very likely so I would not recommend it. Eventually the front can be lifted off.

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 causes an overflow and is not recoverable
	Negative numbers are shown with a "-" in the immediate left hand digit, travelling into the far left (ninth) digit thereby allowing full eight-digit negative numbers
	Divide by zero shows zero and "E” in the far left (ninth) digit and is not recoverable
	Overflow shows the result with "C" (or “E” if negative) in the far left (ninth) digit and is not recoverable
	Memory store is indicated by the decimal point of the far left (ninth) digit
	Negative square roots are allowed and result in a negative number

This scan shows the front of the case removed and the keyboard assembly hinged out of the way.

Quite a compact assembly with the tall components bent over. As the display tube has no mounting brackets or guides it can easily sit at an angle as the tension created by the connecting wires is considerable.

Compare the inside of all three in this series.