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

Size (approx): 68mm x 130mm x 23mm (max)  (w,h,d)
Weight 82g excluding battery

Power:

9V DC from 1 x PP3 size battery.  It accepts an adaptor (DC 9V, 500mW)  through a socket on the left side, just above the display.
Case: Two-piece matt black plastic case that feels quite light and cheap.  The top area has a black printed metallic sticker that sits in its own recess with the brand and model number.  The red plastic display filter is linearly convex to give added magnification and is flush and tilted.  The black plastic keyboard surround has white printed text for the key and switch labels.  The small keys are short travel with a prominent click (my example suffers from bounce).  When shaken the keys rattle like a box of matches.
Display: 8 digit red LED with bubble lens and no ninth digit
Features: Basic four function with percentages
Age: 1976
Manufacturer: Made in Hong Kong (for Dixons).  Serial No. 380479
Comments:

 

Cheap and cheerful with a case design that was used for many other calculators.  The logic is OK with fair recovery and only one minor "divide to negative zero" bug.  The extra magnifying affect of the display filter makes the LED display quite large.  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.  Very cheaply made calculator by Radofin with a case shape familiar from other models.  An earlier Type I model was less effective.

Components: 1 x cpu: Square spiral logo General Instruments C683 7610 (date code week 10 of 1976), 28 pin DIL, 0.6" width black plastic
1 x 8 digit LED unit with individual bubble lens: Optostic
1 x IC: IC6404 5568T, 20 pin underneath in line, 0.6" width black plastic - which may be an resistor array or display driver
2 x resistors
Boards: The main cpu board (Radofin XM 621-20-A) rests on top of the keyboard assembly and is held in place by a couple of plastic lugs.  The two are joined by 15 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.

Logic comments: The (CE) key clears the last entry whilst the (C) key will clear the calculator
Input overflow is suppressed: keying in a ninth digit is ignored
There is automatic constant on all four functions
Overflow shows the result with all decimal points alight and is recoverable using (CE)
Divide by zero shows ".......0." and is not recoverable
Negative numbers are shown with a minus sign in the immediate left digit but as there is no ninth digit to travel into you are limited to seven digit negative numbers
It suffers the divide to negative zero bug: key in (C)(-)(1)(/)(1)(0)(=)(=)... etc until you eventually get to "-0"

The box shown left measures 160mm by 80mm and is 29mm deep.  Printed in blue and black it is a double tuck-end construction.  Made in Hong Kong.