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Calculators: Desktop: Commodore US*10 (aka US 10)

(c) Emil Dudek 2011

Size (approx):

170mm x 226mm x 55mm(max) (w,h,d)
Weight 948g including cable and UK three-pin plug


Mains (230V 50-60Hz) power through a permanently fixed, two wire mains cable of reasonable length.  This enters the calculator on the far right of the top edge. The on/off switch is on the front, the top right.
Display: 10+1 digit orange Panaplex display, the eleventh being used  for input overflow, negative and error indication. 
Features: Standard four functions with switched constant, floating and 4/3/2 fixed decimal modes.  Semi-RPN logic.
Age: 1973
Manufacturer: Commodore, made in the USA, serial number 470926.


Chunky design with a bright display but archaic keys. The logic is reasonable - no major bugs, but the lack of recovery, especially on input overflow is annoying.

Case and Design: Made from two sections of matt black plastic.  There are cooling grills in the area of the on/switch at the top of the front.  An orange plastic display filter sits tilted and inset in its own escutcheon.   Above the display is a recessed area with a plastic logo label which has raised and silver painted lettering.  The rear has a metal "U" shaped leg that can be hinged out to increase the angle that the calculator sits.

(c) Emil Dudek 2011

Keys and Switches: Big chunky keys with long travel and a hollow loud clunk and bounce. A simple colour scheme or white blue and red is not too cluttered.  The constant key "K" is a push-on/push-off switch.  A slide switch selects between floating decimal and 2/3/4 fixed decimal points.
Construction: From underneath, remove the four screws (two large, two small) and the base section will lift off easily.
Boards: The main CPU board (US 10 300027 H MCL-45F (this last number looks to be proceeded by an Hitachi Symbol)) face down in the calculator front and doubles as the keyboard assembly. It is held to the front section with numerous screws, some in pillars some in metal brackets.  These screws have tamper-evident resin.

Components: 1 x cpu: TMS0175C  7337 (week 37 of 1973). 28 pin DIL 0.6" width black plastic
1 x 11 digit Panaplex unit
Large quantity of transistors, diodes, capacitors, resistors and a transformer.

Logic comments: (CE) is used once to cancel the last number entered and (C) to clear the whole calculator.
Input overflow is not suppressed, keying an eleventh digit creates an error state with "C" in the far left (ninth) digit and is not recoverable
The logic is semi-reverse Polish Notation (RPN): to do 5-8 key in (C)(5)(+=)(8)(-=) to give "-3"
There is switched automatic constant using (K) on multiply and divide only
Negative numbers are shown with a minus in the far left (ninth) digit thereby allowing full ten digit negative numbers
Divide by zero shows zero and an upper "n" in the far left (ninth) digit and is not recoverable
Overflow shows the result shifted and an upper "n" (or upper square box if negative) in the far left (ninth) digit and is not recoverable
A slide switch selects between floating decimal and 2/3/4 fixed decimal points
No bugs found.