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Calculators: Handheld: Commodore SR4190R

Size (approx):

80mm x 150mm x 30mm(max)  (w,h,d)
Weight 220g (including batteries)

Power: Rechargeable sealed Ni-Cd batteries from mains adapter. 3x AA, 1.5V cells (3N450AAF). Use adapter DC640, 707, 708 or 709, 6 Volts.
Case: Two-piece stippled black plastic case with chrome painted trim (the remnants of which can still be seen).  Buttons in grey, white, red, green and blue with functions in raised and painted green.  Inset red display filter.
Display: 10 digit red LED  module with bubble lens (eleventh for minus sign) plus two digit (smaller) red LED module with bubble lens (third holds minus sign) for the exponent.
Features: Over 80 functions including poisson, gaussian, integrals, derivatives, probability, hms, factorial, slope, intercept, two memories and conversions (F-C, oz-g, gal-l, m-km, BTU-J etc.)
Age: Commodore's scientific range spans 1974 to 1976.  The date codes on the chips point to 1976.
Manufacturer: Commodore, Made in England. Serial No. 130180, (label) part No. 201345-03.
Comments: With 49 keys is this a button monster or what!  The SR prefix of this period indicates a "scientific model", they used "F" for financial.  Good idea to install rechargeable batteries as this thing would have eaten power.  This is one serious calculator, although the "Made in England" means assembled at best as all the components and boards are Japanese.
Components: 1 x MPS 7200 5177 MOS cpu
2x ITT 546A-SN 7625 display driver (date code week 25 of 1976?)
1 x GHU-01A ESR-C 7643 keyboard decoder (date code week 43 of 1976?)
1 x GHU-01A ESR-B 7623 keyboard decoder (date code week 23 of 1976?)
4 x resistors
1 x diode
2 x capacitors
1 x transistor
1 x voltage regulator
Boards: Three boards; main board (Rev-A201001 ITT & Toshiba) held in by seven screws, keyboard (201 009 Commodore made in Japan 176 902) and display.
Construction: Opened with two screws on the back (lower end being hinged, one has broken on my sample).  Very densely packed inside, despite the size.  Thick ribbon cable joins the three boards.  The display board is held in place by the upper power socket and two moulded forks on the back.  Beware, once apart this calculator is very difficult to get back together again, the batteries and regulator are not held firmly on the back panel, the display is difficult to get positioned - don't do it!
Logic comments: The (C/CE) button is used to clear last entry of a number and pressed a second time to clear the whole calculator.
Overflow on number input is suppressed, typing in a nine digit number ignores the ninth digit.
An overflow error is flagged with an "E" in the eleventh (left most) digit, negative or positive.  Number is not recoverable.
Divide by zero results in a  "E" which is also not recoverable.
There is no constant on any function
There is no indication of memory store - you have to remember it.
Hours, minutes and seconds are displayed with a "-" between them.
Negative numbers are flagged by a "-" sign in the eleventh left digit