The Bowmar MX75, which was made in 1974 is an ambivalent device: On the
one hand, it has got a vintage looking soapbox-like case and is internally
constructed in an old-fashioned way, otherweise it already offers state-of-the-art
calculation power with the four basic arithmetic operations, standard entry
logics and accumulating memory.
For a pocket calculator of 1974, it is inconvinient, that the large
double-sided boards looks like manually designed and populated and even five
ICs were used. There's at first the CPU, a Rockwell A1030PE, made in
may 1974, two ICs DM8895N and two ICs, maybe display driver, DM75494N, all
made in april 1974.
Furthermore, a lot of diodes, resistors, transistors, a handful of
tantal capacitors and even a coil were soldered - such a opulent
assembly was no longer usual in 1974.
The design is classical, almost vintage: With a maximum height of
3.7cm and a size of approx. 12 x 8cm, the calculator indeed looks like a
soapbox and is certainly too big for a shirt pocket. A large part of responsibility
for the height has go the large PCB, which fills the case in full size, then the
three AA cells below, which shall guarantee five hours of continuous
operation, and the angled LED display, which has rather large numbers because
of its large magnifying glass.
Not much responsibility on the height has got the Klixon keyboard, with is
connected by a nine pin socket and is extremely pleasantly to use. Hardly any
other keyboard can compete with a Klixon keyboard: The pressure point
is excact and accompanied by a click, and it can be quicky used without bouncing.
Unfortunately since this type of keyboard was expensive, these keyboards were
not often used.
|inside and batteries|
The MX75 offers the four standard calculation functions, which were
useual these days. It has also got an adding memory function, which can
be enabled and disabled by a switch below the display and read and deleted
by two keys. If the MX75 is in calculator mode, on the display there's
a slash visible:
|display in memory mode|
Empty batteries lead to a "L"
at the first position; Division by zero and overflow are
indicated with a "C" on the left:
|display on errors and overflow|
|Display||8+1 digit LED|
|Number of keys ||20|
|Entry logic (classification) ||ALG (BCBA)|
|1 + 0.000 = ||1.000 (the correct value would be 1.)|
|0 / 0 = ||Error |
|Power supply ||3xAA (internal)|
|Size||12 x 8 x 3.7cm|
|Original Price||DM 398.--|