Rockwell 51R

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Calculators: Handheld: Rockwell 51R (aka Universal Converter)

		Size (approx):	84mm x 157mm x 28mm (w,h,d) Weight 270g including batteries
		Power:	6.0V DC, 4 x AA sized internal rechargeable batteries. It accepts an adapter/charger (Part No. 328R07-001 in the US) through a socket on the top side, in the middle. Warning, you may use the calculator off an the charger whilst charging but it is not to be considered an adapter and left connected indefinitely (battery degradation could occur after approximately 72 hours). Also, do not operate the calculator until you have charged the batteries for five hours. Fully charged batteries will last about three hours. Mine worked of a 4.5V centre positive adapter.
		Case:	Typical early Rockwell with the main case body being dark brown matt plastic whilst the front is made up of the neutral plastic display filter and the cream painted keyboard surround. Above the display the raised logo and brand is painted silver as are the two front edges of the case. The keyboard surround is printed with black text for key and switch labels and also on the lower edge for the "Converter" name and model number. The keys have a loud click and rock from the bottom edge like first generation Rockwell machines.
		Display:	8 digit blue VFD with a ninth symbol cluster for negative and error indication
		Features:	Standard four functions with programmable conversions, fractions, double four function memory. Switches for Imperial/USA liquid measurements, statute/nautical miles and fixed/floating decimal.
		Age:	1974
		Manufacturer:	Rockwell International Microelectronic Product Division, assembled in Mexico, US and foreign parts. Serial number 124144
		Comments:	Lovely solid Rockwell that just about converts everything into everything. Has similar keys to the early Unicom calculators (a company that they bought). The logic is sound but the fractions are a let down as they are nowhere near as good as Casio who managed to display fractions perfectly. The programmable conversion function is easy, two memories is useful but the equals key is in the wrong place. The original case is padded brown plastic, felt lined, with a large top flap that fastens to the front with a metal toggle. There is an internal PVC wallet to hold the manual. It has Rockwell embossed on the front and "Case made in the USA" on the back. In my example the rechargeable batteries still worked!

Components:	1 x cpu: Rockwell A4004PC 7442 (week 42 of 1974), 42 pin DIL 0.6" width 1 x 8 digit VFD module: single slab shaped tube with flat face; ISE DP89A 6914 Japan 1 x 1 symbol cluster VFD tube 1 x Voltage regulator (?): M SFC 8080 426, 8 pin staggered DIL 5 x transistors 4 x diodes 5 x capacitors 17 x resistors 1 x resistor array (I think): PE81170 7420, 14 pin DIL 0.3" width 1 x Ni-Cd battery pack (4 x AA sized batteries wired together): 3074 R.I. #326R04
Boards:	The main cpu board (20168D28F) sits on two plastic lug guides to the front of the case connected to the switch assembly board via a 22-way block connector. The batteries sit on top of the keyboard assembly, held loosely by two plastic lugs.
Construction:	Remove the four screws located under the rubber feet on the rear - the sticky feet come off easily. The rear section then comes off easily.

Logic comments:	The (C) key operates as a cancel entry function on the first press whilst a second press will clear the calculator
	Input overflow is suppressed, inputting a ninth digit is ignored
	Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	There is automatic constant function on all four functions
	Divide by zero shows "0.0.0.0.0.0.0.0." and a large round dot in the far left (ninth) digit and is recoverable using (C)
	Overflow shows the result with all decimal points and a large round dot in the far left (ninth) digit and is recoverable using (C)
	There is no indication of memory - you have to remember it
	Memory functions are accessed by a two or three key sequence: to add to memory one key in (M)(1)(M+). Subsequent operations default to memory one until you select memory two.
	The (CONV) key is used for one of the 112 conversions: the first key touched specifies the units being converted. To convert 25 inches into millimetres key in (2)(5)(CONV)(INCH)(MM) when "635" is displayed.
	The (K>) key is used to store a programmable conversion constant in conjunction with the (A<) and (>B) keys. If the conversion factor for Dollars to Pounds is 1.5 then key in (1)(.)(5)(CONV)(K>). Now to convert £125 into dollars key in (1)(2)(5)(CONV)(A>)(B>) to display the result in dollars.
	Fractions can be converted to decimals using the (A/O) key: To convert 5 ¾ to decimal key in (5)(A/O)(3)(A/O)(4)(=) to give "5.75". To add 3/8 and 5 ¾ key in (3)(A/O)(8)(+)(5)(A/O)(3)(A/O)(4)(=) to give "6.125".
	The F/2 switch changes between floating decimal and two-digit decimal answer mode

main board

The compact main board completely detaches as it is fixed by the lower (white) connector block. Notice the early "bath-tub" shaped VF display with the extra symbol cluster VFD tube to the left.

manual

The 4/1 manual measures 66m by 130mm and is a whopping 92 pages thick in English language only. At this size, it is stuffed with instructions, examples and conversion tables.

Quote: "You now have one of the most versatile calculators in the entire Rockwell line - one that will become more and more useful as U.S. [sic] conversion to the Metric System gets closer.

Quote: "...in a wink it will translate [sic] foreign currency into U.S. dollars.."

Quote: "Rockwell International ...where science gets down to business."