Prinztronic X15 type I

		Home New Stuff Author Links Guest book Web-log	Adverts Bric-a-brac Calculators Components Ephemera Events	For Sale Glossary History Hit or Miss Radios Transport	Ultra Valves Wanted Metal Puzzles Caravan

Calculators: Handheld: Prinztronic X15 (type I) (Dixons)

		Size (approx):	68mm x 130mm x 23mm (max) (w,h,d) Weight 86g excluding batteries
		Power:	9V DC, a x PP3 size battery, 0.5W. Accepts adapter (DC 9V, 500mW) through left side socket three quarters of the way up. It was originally supplied with a battery.
		Case:	Slightly squeaky black matt plastic case. The top area holds a black sticker with white text for the brand and model names and sits in its own recess. The red plastic display filter is horizontally convex to give added magnification. The smooth black plastic keyboard surround is printed with white key labels. The small keys are medium travel with a positive plastic click.
		Display:	8 digit red LED with bubble lens, no ninth digit
		Features:	Basic four function with VAT and constant
		Age:	1975
		Manufacturer:	Made in Hong Kong (for Dixons), serial No. 1510 18019 (and also 1510 32829).
		Comments:	Cheaply made Radofin clone. The logic is OK but the archaic input mode, constant and percentage functions and divide by zero bug is far too much for modern users. The continuing overflow and underflow (the latter without number display) also takes a bit of getting used to. I do like the register that holds a deleted result though. The original case is soft brown plastic with open top and half-moon cut-outs either side: it is a bit of a tight fit. A later type II model was better.

Components:	1 x cpu: Square spiral logo General Instruments CZL550-RA 7519 (date code week 19 of 1975), 24 pin DIL, 0.6" width black plastic 1 x IC: ITT 7105N 7427, 16 pin DIL, 0.3" width black plastic 1 x 8 digit LED unit with individual bubble lens: Optostic 4 x transistors 1 x diode 1 x capacitor 6 x resistors 1 x transformer
Boards:	The main cpu board (Radofin 270275) sits face down rests on top of the keyboard assembly and is held in place by a couple of plastic lugs. The two are joined by 19 very long bare wires.
Construction:	Quite difficult to open as it is held together with internal lugs only. Be careful as damage may result - the plastic case is quite thin in lots of areas. I found the easiest way was to start on one of the sides, levering apart the middle whilst pushing in the front section. The back will eventually lift off. The inside of the rear is embossed with "Property of Radofin Model 15XX).

Logic comments:	No reset on switch on - you usually get a jumbled mess on start up that has be be cleared using the (C/CE) key - this is referred to in the manual
	However, a register holds the last result even after clearing - you can recall it by keying in (X)(1)(=)
	When in number input mode there is no leading zero suppression: i.e. keying in the number five result in the display showing "00000005"
	Results of calculations are shown left leading rather than today's normal right reading
	The (C/CE) key clears the last number entered whilst a second press will clear the calculator
	Input overflow is suppressed: keying in a ninth digit is ignored
	The minus sign is always held in the eighth digit, thereby limiting the display to a seven-digit negative number. Typing in "0" (-) "12345678" results in "-1234567" with no error.
	Overflows do not create an error - just keep on calculating with the most significant eight digits. If you eventually exceed 10⁸⁰ then the result is just zero. It will also hold numbers down to 10^-20 but just show zero until the calculation reaches a number > 10^-8.
	Divide by zero shows "0.0.0.0.0.X.0.8." where the "X" is a cycling, incrementing number, other numbers can be non zero depending on you input number and is not recoverable. Thus 12345678 divided by zero shows "0.2.0.4.5.X.7.8."
	The (VAT) key is a percentage key, to work out 5% of 20 then add it on key in (2)(0)(X)(.)(0)(5)(VAT)(=)(+)
	The constant (K) key works on all four functions: i.e. to add 25 to different numbers key in (2)(5)(=)(K) then (5)(+) to give "30" and (1)(0)(+ to give "35". When dividing the constant is always the divider.
	Squares can be performed by using the constant key: i.e. the square of five can be found by (5)(=)(K)(X) then the cube by (X) again etc
	Reciprocals can be performed by using the constant key: i.e. the reciprocal of five can be found by (5)(=)(K)(÷)(÷)
	No other bugs found

The box shown left measures 160mm by 80mm and is 32mm deep - big enough to accommodate the calculator and a battery. Printed in blue and black it is a double tuck-end construction. Made in Hong Kong.

The manual measures 76mm by 3082mm (when unfolded) as a one colour black fan-fold leaflet. Oddly it refers the the on/off switch on the front like the type II model, but describes the (VAT) key correctly - is there a hybrid in-between model?

Quote: "Your new portable electronic calculator is a product of high technology engineering which provides instant answers to your math problems in the home, office and classroom. Your calculator has the ability to solve complex business and scientific problems. It features an eight digit display but will not overflow. Information is never lost. The tiny MOS "chip" holds numbers from 10^-20 to 10⁸⁰."