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Calculators: Handheld: Commodore Minuteman 3 Metric

Size (approx): 75mm (max) x 105mm x 27mm (max)  (w,h,d)
Weight 96g excluding batteries

Power:

6.0V DC, internal rechargeable battery. 0.2A.  Accepts adapter (undefined) through top end socket in the middle.   Adapter should be 3mm positive centre.
Case: Lovely palm-sized  white matt plastic calculator.  Keyboard surround panel in black plastic and black painted metal display surround.  The latter has a raised and silver painted logo and silver painted "on" label.  Squish but positive keys. Sticking with the red white and blue key colour scheme this compact calculator just oozes quality.  Useful conversion guide on the back panel as well as the front reminder.
Display: 8 digit LED with no lens, ninth digit for minus sign and error flags
Features: Four function plus percentages, four function memory and conversion functions.
Age: 1974
Manufacturer: Made in England.  Serial No. 020086
Comments:

 

The minuteman series was a great concept for sturdy handheld calculators.  The display was a lovely flat LED; the vertical bars being made up of four dots.  The (CE) key acts as a function key to change the operation of a number of keys - very confusing.  Original case is stiff brown plastic with flip over top and popper closing.

Components: 1 x cpu: Unknown MCS 2521A006 0174 (date code week 1 of 1974), 26 pin DIL
2 x chips: One Texas SN75492A M7413 (week 13 of 1974) and one ITT 4S1 7352 (week 52 of 1973) display drivers both 14 pin DIL
1 x nine digit red LED display
1 x transistor
3 x diodes
2 x resistors (one joined between the battery pack and adapter socket)
5 x capacitors
1 x transformer
Boards: Main CPU board is is soldered to the keyboard board underneath.  It has the reference numbers PCB 300148, ART 300349B, ASSY 300350 (with a box for a further mark).  A 17 way ribbon connector joins to the display.
Construction: Remove the two screws on the back and gently prize the calculator back away from the front.  The battery floats but all the boards are attached to the front.

Logic comments: (C) cancels an incorrect numerical entry, pressing a second time clears the calculator
Confusingly (CE) stands for Conversion Entry.
To convert imperial to metric: (1)(0)(CE)(0) converts 10 inches into centimetres
To convert metric to imperial: (3)(0)(4)(8)(CE)(M)(1) converts 3,048 metres into feet
For areas: (1)(0)(0)(CE)(=)(7) coverts 100 sq, miles into sq. kilometres
For volumes: (1)(0)(0)(0)(CE)(M)(-)(4) converts 1,000 cubic metres into cubic yards