Decimo Vatman type III

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Calculators: Handheld: Decimo Vatman (type II)


		Size (approx):	83mm (max) x 132mm x 30mm (max) (w,h,d) Weight 142g excluding batteries
		Power:	6.0V DC, 4 x AA size batteries. Also accepts adapter/charger (6V, 0.3W 3.5mm centre positive) through a top side socket on the right. Take regular alkaline or rechargeable batteries. Dry cell batteries must be removed if using an adapter - says a sticky label inside the battery compartment.
		Case:	Chunky two piece plastic case. The bottom section is light grey, top is matt black. An oversized green display filter, which is flat and almost flush, has a white printed model name and gives a bright display. The Decimo logo is black printed metallic panel that sits in its own recess. The keyboard surround is brushed aluminium and has a black printed on/off switch label. Top is slightly tilted upwards, including the back, which causes the calculator to rock, especially with no batteries to weigh it down.
		Display:	8 digit green VFD display – with a ninth used for negative and overflow indicators
		Features:	Standard four function with percentages and square root
		Age:	1975
		Manufacturer:	Not mentioned, made in Japan. Serial No. 1201425
		Comments:	Classic calculator that has a quality feel in the hand. The logic is poor with many bugs and no recovery. Imbalance on the desk is odd. For those non-UK viewers, VAT stands for Value Added Tax - the purchase tax system in the UK. The original case is soft black plastic with and open top and half-moon cut-outs.

Components:	1 x cpu; Sharp LI2006 5I2 030 (September of 1975?) 28 pin DIL, 0.6" width black plastic 1 x 9 digit VFD; single round faced tube 1 x transistor 4 x diodes 7 x capacitors 9 x resistors 2 x resistor arrays 1 x transformer: Y810
Boards:	The keyboard assembly (CA2022-03) sits on top of the battery compartment and is attached to the main cpu board below with a 16 strong wires.
Construction:	Front can be gently prized off after using the coin guide at the top. Squeeze the grey plastic sides so the lugs separate without breaking and then hinge from the bottom. You do not need to remove the three screws in the battery compartment as they hold the assembly to the back.

Logic comments:	The (CE) key is used to cancel an entry and (C) is used to clear the whole calculator
	Input overflow is suppressed inputting an ninth digit is ignored
	Negative numbers are shown with a "-” in the far left (ninth) digit, thereby allowing full eight digit negative numbers.
	There is an automatic constant on multiply and divide only.
	Overflow shows the result and “C” (or "E" if negative) in the far left (ninth) digit and is not recoverable
	Divide by zero shows zero and “C” in the far left (ninth) digit and is not recoverable
	It suffers the pseudo fixed decimal bug: key in (1)(+)(0)(.)(0)(0)(0)(=) to give "1.000" which remains a three digit decimal number until more digits are needed. If you divide this by 1 you get "1.0000000"
	If suffers the trailing zeros bug: try (1)(SQRT) to give "1.00000000" which remains as an eight digit fixed decimal number as above
	Similarly, calculations tending to zero end up with "0.0000000": try (9)(X)(%)(%)(%)(%)... repeated

	This scan shows the front removed with the hard-wired keyboard sitting above the main cpu board. Whilst the construction is similar to many Decimo calculators, the component layout varies wildly. The majority of components are hidden underneath the keyboard assembly.