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Calculators: Handheld: Rockwell '76 (version of the 18R)

Size (approx): 75mm (max) x 155mm x 23mm (max)  (w,h,d)
Weight 130g excluding batteries


9.0V DC, 1xPP3 size battery.  Also accepts adaptor (undefined) through top end socket on the left. There is an on/off sliding switch on the left hand side about half way up.
Case: Sturdy stippled dark blue plastic case with white keyboard surround.  The latter is printed with blue text and lines.  Red inset display cover.  Lovely lozenge-shaped keys in red have a positive click and work well.  The raised Rockwell logo and two vertical edges are painted silver.  
Display: 8 digit LED with bubble lens with no ninth digit
Features: Four function plus percentages and two function memory.
Age: 1975/6
Manufacturer: Rockwell International, Microelectronic Product Division, Anaheim CA 92803.  Unknown serial number as my example is missing its back label.


An interesting variation on this classic looking calculator made for the bicentennial anniversary of the American Revolution.  The logic is a little frustrating because of the seven digit limit to negative numbers and the pseudo fixed decimal bug.  Minimum components, late date for chip week code and apparent rev 03 reference number means this is a late model.   This is a red, white and blue version of the 18R.  This calculator was also built as the House of Fraser model 18F in a dark blue case with white buttons.

Components: 1 x cu: Rockwell B5000CB 7544 (week 33 of 1975), 42 pin staggered DIL, 0.6" width ceramic with metal cap
1 x 8 digit plus one symbol bubble lens LED module
2 x capacitors
2 resistors
That's it!
Boards: Keyboard assembly is attached to the main board by the back screws.  Nine pins self located into sockets on the main board.  Main CPU board ref 20167D67-03
Construction: Remove the four screws on the back.  Gently pull out the front keyboard which hinges up from the display surround.  Pop off the display surround by pulling it upwards. Main assembly can be removed by slightly twisting away from the on/off switch.

Logic comments: (CE/C) cancels an incorrect numerical entry, pressing a second time clears the calculator
An error results in the display lighting up all decimal points which is recoverable using of (CE/C)
Divide by zero results in "" which is recoverable using of (CE/C)
Negative numbers art shown with a minus sign to immediate left of a number, but as there is non ninth digit you are limited to seven digit negative numbers.
Input overflow is suppressed, keying in a ninth digit is ignored
There is no indication of memory store - you have to remember it
To cancel the memory, store zero
It has automatic constant on all functions
It suffers the pseudo fixed decimal bug: key in (1)(+)(2)(.)(0)(0)(=) to get "3.00" which remains a two digit fixed decimal format until more are required or you use multiply of divide