Prinztronic Asset

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Calculators: Handheld: Prinztronic Asset

		Size (approx):	80mm x 125mm x 28mm (w,h,d) Weight 122g excluding batteries
		Power:	6V DC, 4 x AA size batteries. It accepts an adapter (6V DC, 0.3W, centre negative) through a socket on the top side to the right. 0.3W.
		Case:	Two piece dark brown and cream matt plastic case. A neutral plastic display filter has a black border and is inset and gently tilted. Below this a black printed metallic label sits in its own recess and contains the brand and model name. The keyboard surround is matt black plastic and reminiscent of the Commodore style. The small keys are short travel with a soft click on return. Inside the battery compartment is a labelled hole for a switch to change between normal and rechargeable batteries - but this is not utilised.
		Display:	8 digit green VFD with a ninth digit for negative and error indication
		Features:	4 function calculator with percentages
		Age:	1975
		Manufacturer:	Prinztronic (Dixons), serial number. 46488, on the battery cover, made in Taiwan.
		Comments:	Palm-sized calculator that is strikingly similar to some Commodore models. The logic is quite good but my example appear to suffer from various "around zero" bugs that may be due to a malfunction. The original case is black plastic with external stitching to create very square edges, with an open top

Components:	1 x cpu: NEC µPD274C K48031 (1974 date code), 28 pin DIL, 0.6" width black plastic 1 x 9 digit VFD unit: single glass tube round face 6 x diodes 4 x capacitors 22 x resistors 1 x power supply module: Mannics DC25-2712 7517 (week 17 of 1975)
Boards:	The keyboard assembly sits lose on top of the battery compartment and is joined to the main cpu board (MK 800F) below via 15 strong wires (three of which are actually diodes). The main board is held to the rear with two plastic pillars with rubber sleeves. Component count is kept to a minimum by using a power supply module.
Construction:	Tricky to open as it is held together by internal lugs only. If you must try, use a soft blunt instrument (like a wooden stirrer) to lever off the front section whilst pushing in the rear section edge. The front will eventually lift off.

Logic comments:	The (CE) button is used to clear the last number entered and (C) clears the whole calculator
	Overflow of number input is not suppressed, keying in a ninth digit results in an overflow which is recoverable using (CE)
	There is automatic constant on all four functions
	Overflow shows the result and "C" (or "E" if negative) in the far left (ninth) digit and is recoverable using (CE)
	Divide by zero shows zero and "C" in the far left (ninth) digit and is not recoverable.
	Negative numbers are flagged by a "-" sign in the far left ninth digit thereby allowing full eight digit negative numbers
	My example suffers various around zero bugs: key in (1)(-)(1)(=) results in "-0", repeated (=) adds one, repeated (-)(1)(=) just results in "-0". This appear to be due to the negative constant function switching to positive - and may be a malfunctioning IC - can anyone verify if their model does the same?

With the front section removed you can easily see the main cpu board. Impressively small and dense, it uses an uncommon "Mannics" power supply module to keep the component count down (hence no discrete transistors. It even takes the advantage of using three of the keyboard connecting wires to hold in-circuit diodes.