Commodore SR4190R

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Calculators: Handheld: Commodore SR4190R

		Size (approx):	80mm x 150mm x 30mm(max) (w,h,d) Weight 220g (including batteries) 152g (without)
		Power:	6V sealed rechargeable batteries (3 x AA-sized cells). The adapter/charger is used through a socket on the top side, in the middle. Use adapter DC640, 707, 708 or 709, 6 Volts, (centre positive).
		Case:	Large, tilted and bowed case made from textured black plastic. The heavily inset, tilted and flat red plastic display filter gives a clean bright image though with a narrow angle of view. A section at the top has a raised and (originally painted silver) brand name. Bold coloured keys in red, blue, green, grey and white are quite small, squishy and wobbly. The front outer edge was also originally painted silver but has worn on my example.
		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.) and much more. Nearly 90 functions as far as I can gauge.
		Age:	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". 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. The logic appears sound with extra precision but the lack of recovery and constant function is annoying. Remarkably, the batteries on my sample still work!

Components:	1 x MOS MPS 7200 5177 cpu, 40 pin DIL 0.6" width 2x ITT 546A-SN 7625 display driver (date code week 25 of 1976) 16 pin DIL 0.3" width 1 x GHU-01A ESR-C 7643 keyboard decoder (date code week 43 of 1976) 16 pin DIL 0.3" width 1 x GHU-01A ESR-B 7623 keyboard decoder (date code week 23 of 1976) 16 pin DIL 0.3" width 1 x 10 digit LED module with individual bubble lens 4 x resistors 1 x diode 2 x capacitors 1 x transistor 1 x voltage regulator 1 x 3AA sized Ni-Cd rechargeable battery unit: Saft OS2 124731 made in France
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!
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.

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 an eleven digit number ignores the eleventh digit.
	An overflow error is flagged with an "E" in the eleventh (left most) digit, negative or positive and 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 thereby allowing full ten digit negative numbers
	Calculations appear to be to 12 digits. Try this; "1.000000001" then (square root), which display "1", now (-)(1) gives 4.9 x EE-10
	The change sign function can be used in mid number entry
	Upper functions are accessed by a two key stroke system: use the (F) first.

	Once open you can see the complex fit inside. Everything is orientated to getting the rechargeable batteries in the top area. These fit into two guides (along with the voltage regulator) on the back. Most of the components (including the main IC) are hidden by the numerous ribbon cables.