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Calculators: Handheld: Prinztronic MC100

Size (approx): 112mm x 175mm x 48mm (max)  (w,h,d)
Weight 480g excluding batteries and carry strap


9V using 6 x AA size batteries.  It accepts an adaptor (model MC100A, 0.7W)  through a three-pin socket on the top side just left of the on/off switch.  Battery life is quoted at 5 hours for manganese and 15 hours for alkaline.  The battery compartment has a black ribbon pull to aid battery removal.
Case: The main case is made from a two-piece dark blue matt plastic frame with a silver-coloured plastic piece for the keyboard surround and edging panels.  The on/off switch sits at the top front, in its own recess with white printed label text. Above the display is a black printed metallic sticker in its own recess with the brand and model number.  A green plastic display filter is inset and tilted with the case.  The large keys are long travel with a hollow plastic clunk making it like early desktop.  The left side has a sturdy metal clasp for a black woven carry strap.
Display: 8 digit green VFD  with an extra symbol cluster for display shift, negative, memory, battery low and constant indicators
Features: Standard four function with change sign, three function memory.  Semi RPN (Reverse polish notation)  logic.
Age: 1973
Manufacturer: Prinztronic, Dixons International, made in Japan, serial number D0000383.


This heavy, well built monster just about fits in the hand but is happier on the desktop.   Though Prinztronic tried to push this as a "pocket" calculator.  As well as the archaic semi-RPN input, the logic is poor, with no recovery and plenty of bugs.  However, the memory and 16 digit answers is useful. The original case is soft black padded plastic with a side-bottom-side zip that allows the front to hinge off   There is an internal plastic strap, with popper to keep the calculator in place.  There is even a hole for the carry strap, but not the charger cable.

Components: Main board:
1 x cpu: Rockwell 15340PA 7334 (date code week 34 of 1973), 42 pin staggered DIL, 0.6" width black plastic with metal cap
2 x IC: Toshiba TM4356P 3-F (June 1973), 20 pin DIL, 0.3" width black plastic
0 x transistors
10 x diodes
1 x capacitors
15 x resistors
4 x resistor arrays
Power supply board:
5 x transistors
12 x diodes
12 x capacitors
7 x resistors
1 x transformer
Boards: The main cpu board (PWBE 1116) is mounted face down on top of the keyboard assembly and held in place by two sturdy metal brackets and held by two screws.  A smaller power supply board is also held face down and held in place by a plastic bracket and two screws. These two board are connected together by a clear plastic five-way plug and socket (and a one-way one) to allow easy servicing.   Eleven wires connect the main board to the keyboard assembly.  The display tubes are held in place by another sturdy metal bracket.
Construction: Remove the two screws from the rear of the case.  Then remove the two longer screws from within the battery compartment.  This rear section can now be gently pushed upwards to remove it.

Logic comments: The (C) key is used once to the last entry whilst a second press will clear the calculator
Input overflow is not suppressed: keying in a ninth digit results in an overflow "" which is not recoverable
There is selected constant by the (K) key on multiply and divide only and it is indicated by the "K" display in the right symbol cluster.  For multiplication the constant becomes the multiplicand (first number) whilst in division the constant becomes the divisor (second number).
Double capacity calculations (up to 16 digits) are possible using multiplication and division but not with addition and subtraction.  In multiplication switch between the upper and lower digits of the product by depressing the (<->) key.  However, when you use a double capacity number to multiply another the lower eight digits are regarded as zero.  Also if you use a double capacity number as a dividend only the upper eight digits are obtained as a result.  The lower eight digits are cleared to zero but the decimal point will be in the right place.
Double capacity display is indicated by "<->" in the far right symbol cluster
This "<->" indicator is also used as a "battery low indicator
Overflow shows "" and is not recoverable
Divide by zero shows "" and is not recoverable
Negative numbers are shown with a minus sign in the right hand symbol cluster thereby allowing up to 16 digit negative numbers
The logic is semi-RPN or arithmetic, i.e. to calculate 3-4 key in (3)(+=)(4)(-=)
Memory store is indicated by a "I" displayed in the far right symbol cluster
Overflow in memory is flagged and retains the original number
The memory is not double capacity so numbers larger than eight digits, but smaller than 17 are held with no lower digits
Change sign can be used in mid number entry but not before
It suffers the negative zero bug, key in (1)(+=)(2)(-=) to give "-1" then (1)(+=) to give "-0"
It suffers the pseudo fixed decimal bug, key in (1)(+=)(.)(0)(0)(0)(+=) to give "1.000"  which remains a fixed three decimal digit number until you need more digits or use multiply or divide.
It suffers the divide to negative zero bug: key in (C)(K)(1)(+/-)(/)(1)(0)(=)(=)... etc until you eventually get to "-0"

Prinztronic MC100 manual

The manual measures 150mm by 121mm and is 40 pages in all.  The cover is half-tone blue and black whilst the inner pages are blue, black and red.  It is in English language only and printed in Japan.  It has loads of specification, examples, instruction and hints.  Did people have bigger pockets in the 1970s?


"The amazing Prinztronic MC100 incorporating one ELSI (Extra Large Scale Integration) marks another major advancement in the world of space age miniaturization.  Years of pioneering research in electronic engineering has led to the development of this most remarkable personal electronic calculator.  The Prinztronic MC100 with its memory register and double capacity mode offers maximum portability with a wide range of mathematical versatility. Calculations are carried out on the MC100 with amazing speed, efficiency and the upmost [sic] reliability."

" 'Zerosupress' system make reading figures easier."

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