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Calculators: Handheld: Prinztronic Micro

Size (approx):

73mm x 105.5mm x 27mm (max) (w x h x d)
Weight 142g not including batteries.

Power: 6.0V DC using 4 x AA size batteries, 0.5W.  It does not accept an adaptor. The on/off switch on the left hand side is a press-and-slide type.  Quoted lifetime for "dry" batteries is 15 hours.
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 red display filter is raised and flat with the letters K (for constant) and B (for battery level) printed in white.  The display is clear, not too bright but has a wide angle of view.  The keys are quite squishy, rock about a bit but work well.  The battery compartment has a ribbon pull to aid battery removal.  There is a metal tag for a carry strap on the top - much better than the plastic ones you normally get.
Display: 8 digit red LED (flat dot type) with no ninth digit but separate red LEDs for constant and low battery indication.  There is an addition horizontal bar to the far right of the display.
Features: Standard four functions and constant, RPN logic.
Age: 1972 - one of the very first pocket calculators.  Listed price was 49 at the time.
Manufacturer: Dixons International, made in Japan.  Serial number D0101207.
Comments: Very early compact and solid feeling calculator with the best type of LED display.  I never did understand the battery indicator idea - just as you batteries are running low then an extra LED lights up to drain them even more!  Archaic logic and numerous bugs make it annoying to use but an early classic compact calculator all them same.  The original case is soft black plastic with a zip that covers top, side and half-bottom of the case.  The strap can be put through a gap in the top.  Very similar is shape and design to the Sharp EL-801 so I suspect they actually made it.  Inside is marvellous; extreme high density components and connecting blocks to take the whole thing apart - wow!  See a brochure.

Components: 1 x cpu: Toshiba T3103 E, 28 pin DIL  0.6" width
1 x IC; Toshiba T1271 E, 16 pin DIL 0.3" width
8 x single flat red LED display units
2 x point red LEDs and one horizontal bar red LED unit
12 x transistors
3 x diodes
36 x resistors
1 x variable resistor
4 x capacitors
0 x transformer
Boards: The keyboard assembly (2910020) is attached to the front by four screws.  A 13-way connecting block joins to the main cpu board (4073PWB-A) which also connects to the display board (4083PWB-A) via a 13-way connecting block.
Construction: Remove the screw from the top and the rear section will hinge off from the bottom.  The battery compartment has two internal tags which slot against two more on the main assembly to make contact.

Logic comments: The (C) key is used to clear the calculator there is no cancel entry function
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 "-" to the far right of the digits thereby allowing full eight digit negative numbers
There is selectable constant on multiply and divide by pressing the (K) key.  An LED lights up by the letter K to remind you.
Divide by zero shows "........" and is not recoverable
Overflow shows "........" and is not recoverable
There is a low battery indicator "B" which lights up when fresh ones are required
It suffers the trailing zero suppression bug on the result of division; key in (9)(/)(5) and you get "1.8000000" which continues into the next calculations. 
It suffers the pseudo fixed decimal bug: (1)(+)(.)(0)(0)(0)(=) gives "1.000" which remains a fixed three digit decimal unless more are needed or you use multiply or divide
It suffers the negative zero bug: (1)(+=)(2)(-=) gives "-1" now ad one: (1)(=+) to give "-0"
The logic is semi-reverse polish notation so takes a bit of getting used to; to work out 9-5 key in (9)(+=)(5)(-=) which shows "4".

manual

 The manual measures 148mm x 107mm and is printed in blue and black throughout its 16 pages.  The second half is devoted to examples, but financial calculations are shown with dollars - odd for a British calculator.  Printed in Japan.

Quote: "Our pioneering research (joke as they did not make it - Ed!) and achievement in electronic engineering have finally developed the ultra compact and efficient machine.  Newly developed the Prinztronic Micro calculator is a typical pocket-sized calculator having as many features as possible."

Quote: "Super-compact, space-age styling".

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