Decimo Vatman Memory

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Calculators: Handheld: Decimo Vatman Memory


		Size (approx):	not done yet 83mm (max) x 132mm x 30mm (max) (w,h,d) Weight 140g excluding batteries
		Power:	6.0V DC, 4 x AA size batteries, 0.3W. Also accepts adapter/charger (undefined) through a top side socket on the right. The on/off switch is in the middle of the top side and is a three position switch for On/Off/Charge. A note on the back sticker reminds you to only use the charge position with rechargeable batteries in place.
		Case:	Chunky two piece matt plastic case where the bottom is light grey and the top black. Oversized, wrap over green display filter has a white printed model name. It has frosted internal edges around the display and gives a very clean bright image. A black printed metallic sticker with the brand name sits in its own recess. The keyboard surround is brushed aluminium. Top is slightly tilted upwards, including the back which causes the calculator to rock, especially with no batteries to weigh it down. Keys are squishy but positive to use.
		Display:	8 digit green VFD display with a ninth digit for negative, memory and error indicators.
		Features:	Basic four function with percentages, change sign, square root and four function memory
		Age:	1975
		Manufacturer:	Decimo Electronic Handy Calculator, made in Japan, serial No. M 108492
		Comments:	Classic calculator which has a quality feel in the hand. The logic is quite poor with no recovery and various major bugs. The imbalance on the desk lets this otherwise nice design down. For those non-UK viewers, VAT stands for Value Added Tax - the purchase tax system in the UK. The original cover is soft black plastic with a flip over lid and front popper closing.

Components:	1 x cpu; Sharp LI2003 5J2 013 (September 1975), 28 pin DIL, 0.6" width black plastic 1 x 9 digit VFD; single round faced tube 2 x transistors 4 x diodes 6 x capacitors 7 x resistors 2 x resistor arrays 1 x transformer: DCT-27 Zebra
Boards:	The keyboard assembly (3002M LI2003 Gico Japan) sits on top of the battery compartment and is attached to the main cpu (D-23-TC-0) board below with a 11-way ribbon block.
Construction:	The front can be gently prized off after using the coin guide at the top. Squeeze the cream plastic sides so the lugs separate without breaking.

Logic comments:	The Clear key (C/CE) is used once to clear an input number, and a second time to completely reset the calculator
	Overflow on the input of a number is suppressed, keying in a ninth digit is ignored
	There is automatic constant on multiply and divide only
	Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	Overflow shows the result and "C" (or "E" if negative) in the far left (ninth) digit and is not recoverable
	A divide by zero shows zero and "C in the far left (ninth) digit and is not recoverable
	The change sign function can be used in mid number entry but not before
	Memory store is indicated by the decimal point of the far left (ninth) digit
	The recall memory key (RM) should really be called the (RM/CM) key as a second press clears the memory
	Overflow in memory leaves the original contents intact
	Negative square roots are not allowed and result in zero and "C in the far left (ninth) digit and is not recoverable
	It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1" now add one (+)(1)(=) to give "-0". It also suffers the divide to negative zero bug.
	It suffers the pseudo fixed decimal bug: key in (1)(+)(.)(0)(0)(0)(=) to give "1.000" which remains a fixed three digit decimal number until you need more digits or use multiply or divide

Here you can easily see the components crammed into the top of the case - the whole of the bottom being taken up by the keyboard assembly on top of the battery compartment.