Radofin 1660

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Calculators: Handheld: Radofin 1660

		Size (approx):	68mm x 130mm x 23mm (max) (w x h x d) Weight 84g not including batteries.
		Power:	9.0V DC using 1 x PP3 size battery. It accepts an adapter (DC 9V 500mW) through a socket on the left hand side just above the display.
		Case:	Compact model made from a two-piece brown and beige matt plastic case. A raised and grooved area sits at the top with black printed text for the brand name. The convex (magnifying) red display filter is slightly tilted and gives a clean image of the rather narrow view digits. The keyboard surround is printed with black and brown text. The keys are short travel, loud click type. They are quite loose so the whole thing rattles like a box of matches.
		.Display:	8 digit red LED (individual bubble lens) with a ninth digit for negative, memory, function and error indicators.
		Features:	Standard four functions with reciprocal, pi, square root, logs, trigs and five-function memory. 5+2 scientific display mode. The display is left leading rather than the common right reading of today’s calculators.
		Age:	1976
		Manufacturer:	Radofin Electronics Ltd., made in Hong Kong, serial number 1660 19227
		Comments:	Very cheaply made calculator similar to the Prinztronic SC1001M with a case shape familiar from other models. The logic appears OK but the lack of recovery and limited scientific mode digits let it down, but there are no major bugs.

Components:	1 x cpu: General Instruments CF596 7552 (week 52 of 1975), 28 pin DIL, 0.6" width black plastic 1 x IC: National Semiconductor DS8872N 609, 22 pin DIL, 0.3" width black plastic 1 x 9 digit LED unit with individual bubble lens 2 x transistors 0 x diodes 1 x capacitor 3 x resistors 1 x transformer
Boards:	The main cpu board (Radofin XM-141-20-A) is held over the keyboard assembly by two plastic lugs. There are very long connecting wires to the keyboard assembly which is fixed to the front also by plastic lugs and some guides.
Construction:	One of those difficult ones that is held together with nothing but lugs - if in doubt do not try as damage may result. The easiest way I found was to pop the right hand side lugs by levering out the back section. The inside rear of the case on my example is embossed with "Property of Radofin Model X-4" which I suspect refers to the plastic mould.

Logic comments:	The (C/CE) key is used to once cancel an entry whilst a second press clears 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 automatic constant on all four functions
	Divide by zero just shows “E0.” Starting in the far left (ninth) digit and is not recoverable
	Overflow just shows “E0.” starting in the far left (ninth) digit and is not recoverable
	There is indication of memory store by the bottom right vertical segment of the far left (ninth) digit.
	The higher functions are accessed by a two key system; i.e. for square root of 6-key in (6)(F)(1). An “”F” is displayed in the far left (ninth) digit to remind you of function mode.
	Negative square roots are not allowed and show “E0.” starting in the far left (ninth) digit and is not recoverable
	The scientific display mode is accessed by (F)(EEX) or automatically if the number gets bigger than eight digits. It can display a five-digit mantissa and two-digit exponent. (CN) change notation can get you back to scientific mode after (EEX).
	The memory exchange function (MEX) swaps the current display for the memory content

Radofin 1660 box

The box on the left measures approximately 75mm by 140mm and is 26mm deep, so just about accommodates the calculator. It is double tuck-end construction and printed in Orange, green, light and dark grey.

Made in Hong Kong.

manual

The black and white manual measures 74mm by 134mm and is 34 pages in total.

In English only, it gives plenty of definitions, descriptions and accuracies of functions, examples and problem functions.

Ref No. 1B-140-62-A

"This calculator will provide you with rapid, accurate solutions to a wide range of problems. It is an electronic slide rule with eight digit accuracy plus the standard calculator functions of addition, subtraction, multiplication and division. A memory stores intermediate results for easy recall. Automatic constant retains a number for repetitive operations plus integer powers of a number without need of a special key or switch."