Citizen 830R

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Calculators: Handheld: Citizen 830R

		Size (approx):	87mm(max) x 150mm x 33mm(max) (w,h,d) Weight 198g excluding batteries
		Power:	6V through 4 x AA size rechargeable battery pack. It accepts an adapter/charger (CTZ-800R, centre negative) through a socket on the top side two thirds towards the left. The on/off switch is on the left hand side and is three position DC/Off/AC. Battery compartment is accessible as any disposable battery calculator.
		Case:	Two-piece light and dark grey smooth plastic case. The green plastic display filter has a frosted border, is inset and prominently tilted. Below this are two metallic stickers printed black and sitting in their own recesses for the brand with model number and the memory switch positions. The keyboard surround is brushed aluminium panel, slightly raised. The large keys are soft touch with a soft metallic click on return.
		Display:	8 digit green VFD, with an additional symbol cluster on the left for negative, memory and error indication.
		Features:	Standard four functions with percentages, change sign, square root, squares and four function memory. Additional switch for memory accumulation.
		Age:	1976
		Manufacturer:	Citizen Business Machines Inc., made in Japan, serial number 603 81771.
		Comments:	Sturdy calculator of the familiar Citizen colour scheme that is equally home as a desktop model or a slight large hand-held. The logic appears sound enough with pretty good recovery and no obvious bugs. The original case is soft dark brown plastic with red stitching and Citizen embossed on the front. It has an open top and square cut-outs either side.

Components:	1 x cpu: NEC µPD946C R61726, (date code 1976), 28 pin DIL, 0.6" width black plastic 1 x 8 digit VFD with symbol cluster display flat face single tube: Futaba 9-ST-04 6C (March 1976) 2 x transistors 7 x diodes 7 x capacitors 8 x resistors 2 x resistor arrays 1 x transformer: DCT-31 Zebra 1 x rechargeable battery pack
Boards:	The keyboard assembly (GICO GK 132-2 830R-A PPB946 K-2 51-3-13) (date code 13 March 1976) sits above the battery compartment and is attached the the lose main board (830R-B) (second revision) below with a 14 way ribbon cable.
Construction:	Held together by internal lugs only, I found the best way was to prize of an edge, at the bottom first, then the bottom and travel up both sides. Push in the grey side as you lever out the rear with a soft blunt instrument to avoid damage. The front will easily lift off, slightly hinging from the top edge.

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, inputting a ninth digit causes an overflow error which is recoverable by dividing by ten
	Negative numbers are shown with a "-" in the far left symbol cluster thereby allowing full eight-digit negative numbers
	Overflow shows the result with "l" in the upper far left symbol cluster and is recoverable by dividing by multiples of ten
	Divide by zero shows zero and "l" in the upper far left symbol cluster and is not recoverable
	The change sign function can be used in mid number entry but not before
	Negative square roots are allowed and result in a negative number
	Memory store is indicated by a "M" in the lower far left symbol cluster
	You can switch in an automated accumulation mode for the memory which only adds the result of a multiplication or division on the press of the equals key - what's the point of that?
	Oddly enough an overflow in memory is not flagged as an error until you try and recall the memory where the shifted end result is restored

The image left shows the calculator with the front removed. A familiar layout with a GICO keyboard assembly sitting on top of the battery compartment and the main cpu board, like many Decimo et al calculators.

The cpu is underneath the top row of keys, along with most of the power supply components.