Prinztronic 80

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Calculators: Handheld: Prinztronic 80 (possibly aka Mini 80)

		Size (approx):	81mm x 146mm x 32mm (max) (w x h x d) Weight 236g excluding batteries.
		Power:	6.0V DC using 4 x AA size batteries, 1.2W. It does not accept an adapter. The on/off switch on the left hand side in line with the display. Battery lifetime can not be very long with this power requirement. A battery compartment ribbon pull helps you to remove the batteries.
		Case:	The two-piece case in blue smooth plastic is accentuated by a shaped panel which is painted silver. This panel has a metallic, black printed label sat in its own recess with the brand and model number. The clear windowed plastic display filter is flat and flush with its own raised escutcheon. It lets in all the light so you can see the display unit. The large keys are medium travel with a metallic click on return. Each key has its own printed plastic-coated label. A constant switch has a recessed black printed metallic label. There is a metal tag for a carry strap on the top.
		Display:	8 digit orange gas discharge with a discrete red LED for negative indication
		Features:	Standard four functions with register exchange and switched constant, RPN (arithmetic) logic.
		Age:	1973
		Manufacturer:	Dixons International, made in Japan, serial number D482612
		Comments:	Very early compact and solid feeling calculator with glorious orange display - exposed to all. No power adapter is a bit of a disappointment for such a power-hungry calculator though. As you would expect the logic is pretty poor with no recovery, no input suppression and the negative zero bugs. The original case is soft black plastic with a flip over top flap and front popper closing. From the board ID it appears to be a branded Toho model.

Components:	Main Board: 1 x cpu: NEC D271D K34226, 28 pin DIL 0.6" width white ceramic with metal cap 1 x IC: NEC µPD261C K2Z046, 20 pin DIL 0.3" width black plastic 1 x 8 digit gas discharge module: Flandipak CD802 Matsushita 3D1 (April 1973 date code) 1 x point red LED 15 x transistors 8 x diodes 11 x capacitors 39 x resistors 2 x resistor arrays 1 x transformer Display driver board: 10 x transistors 1 x diode 8 x capacitors 16 x resistors
Boards:	The keyboard assembly is attached to the front by nine screws. It connects through eight coloured tied wires to the main cpu board. A small display board sits on top of the display driver board (T0H0 Mini-80) which sits above the main cpu board. These are held in place by two long screws at the top with plastic guide pillars. There is yet another piggy-back board on the main cpu board, with its own metal box shroud holding the power driving circuit. Several pieces of card insulate the boards.
Construction:	Remove the two long screws from the rear by the battery compartment and the short one on the top edge. The front section will come away easily - hinge to the right. Note the location of the carry strap tag as it will fall out easily.

Logic comments:	The (CE) key is used to clear the last number entered whilst (C) clears the whole calculator
	Input overflow is not suppressed inputting an ninth digit results in all eight decimal points alight and is not recoverable
	Negative numbers are shown with a LED to the far lower right of the digits thereby allowing full eight digit negative numbers
	There is selectable constant on multiply and divide by pressing the (K) key
	Divide by zero shows "........" and is not recoverable
	Overflow shows "........" and is not recoverable
	The (R) key is a register exchange - switching the current number for the last one entered in a chain
	The logic is reverse polish notation so takes a bit of getting used to; to work out 9-5 key in (9)(+=)(5)(-=) which shows "4".
	It suffers the negative zero bug: key in (1)(-=) to give "-1" now add one by (1)(+=) to give "-0"
	It suffers the divide to negative zero bug: switch [K] on then key in (1)(-=)(÷)(1)(0)(+=)(+=)(+=) etc to eventually give "-0"

	With the front removed you can see the display board and the display driver board underneath it. Eight transistors, eight capacitors and eight resistor pairs for the eight digits. Notice the discrete red LED on the bottom left of the display board as well. Driving components for this are underneath the display board. These two boards are joined by 16 stiff wires and they hide the CPU board which sits in the well below.
			The gas-discharge display gives this calculator an unusual orange display. Note how the digits have heavily truncated lower corners. Also, the decimal point is quit ea large horizontal stroke - perhaps trying to cover UK/USA decimal points and European decimal commas. You can also see the isolated red LED for the negative indicator meaning this number is "-12345678."