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Calculators: Handheld: Rockwell 61R (aka Advanced Slide Rule)

Size (approx): 84mm x 156mm x 24mm (max)  (w,h,d)
Weight 278g including battery pack.


6V DC, 1xNi-Cd battery pack.  It accepts an adapter/charger (undefined but supplied, 6V centre positive) through top end socket in the middle.  Charging time is quoted as five hours, optimum operating time three hours.
Case: Sturdy stippled dark brown plastic case with light beige metal keyboard surround.  There is an oversized stippled neutral inset display filter with a smooth window. It has a raised Rockwell logo which along with the front edges is painted silver.  Lovely rocking titled up square keys from the earlier Unicom days and work well.  The keyboard surround is printed in dark  brown for the key and switch labels.  The model number is printed on the lower edge of the keyboard surround. 
Display: 8 digit blue VFD with an extra symbol cluster (to the far right) for negative and error indicators.
Features: Four function plus logs, trigs, powers, square root, change sign, register exchange, reciprocal, pi, data recovery and six function memory.  Degree / radian switching.
Age: 1974
Manufacturer: Rockwell International, Microelectronic Product Division, Anaheim CA 92803.  Assembled in Mexico, US and Foreign parts.  Serial number 156740.


Typical Rockwell with large display and a sturdy design helped by a strong metal keyboard surround.  The logic is very robust with good recovery and only let down by negative square roots. Original case is brown padded plastic with a flip over top flap that has a metal toggle closure at the front.  It is embossed with the word Rockwell and has an internal PVC pocket to house the manual. 

Components: 1 x cpu: Rockwell A4002 15472PA 7431 (week 31 of 1974), 42 pin staggered DIL, 0.6" width
1 x 8 digit VFD, single tube flat face module; ISE DP89A Japan 6591
1 x VFD symbol tube: line and dot display single tube, round face
3 x transistors
1 x rectifier (?): Motorola SFC 8080 341 8 pin staggered DIL 0.3" width
6 x diodes
4 x capacitors
15 x resistors
1 x resistor array (?); PE81770 7415, 14 pin DIL, 0.3" width
1 x transformer
1 x Ni-Cd battery unit (4 x AA sized batteries)
Boards: The keyboard assembly sits embedded between the metal front and a plastic middle section.  It is joined to the main cpu board via a 19-way post and socket strip.
Construction: Remove the four screws on the back.  The whole back lifts off easily.

Logic comments: (C) cancels an incorrect numerical entry, pressing a second time clears the calculator
The (DR) function allows data recovery; i.e. it cancels the current number and reverts back to the last register held.
Input overflow is suppressed, typing in nine digits ignores the ninth
There is automatic constant on all four functions
Negative numbers are shown by a minus in the far left symbol cluster thereby allowing full eight digit negative numbers.
The change sign function can be used in mid number entry
Divide by zero results in zero and a large dot in the far left symbol cluster and is recoverable by using (C)
Overflow shows the result with a large dot in the far left symbol cluster and is recoverable using (C)
Higher functions are accessed by pressing the (F) key first.  Pressing (CF)  will cancel the function mode but there is no indication
Memory store is not indicated - you have to remember it
(X<>M) exchanges the contents of the memory with the display and register exchange (<>) swaps the two numbers in an operation.
Negative square roots are not allowed, result in an error and is surprisingly not recoverable

Condition too 
poor to scan

The manual measures 68mmm by 130mm and has a full colour cover.  The 96 internal pages are printed in black and are in English only.  This is therefore an extensive manual with loads of examples and instructions.

The rear has the marketing strap line "...where science gets down to business"

? Rockwell International 1974, ref. 2520-D-62-R2-407, Litho in USA.

The scan on the left shows the main cpu board.  Note the dominating large VFD display module and the extra display tube on the left with the negative and error (the dot) symbol.

Help!  I believe the white DIL package underneath the first and second digits is an early resistor array.  I also believe that the black package in line directly above the display is a diode array (unwired bridge rectifier perhaps).  Can anyone help?

Notice also the connector to the keyboard assembly at the bottom which makes removal of the whole cpu board easy.