Sovrin 438

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Calculators: Handheld: Sovrin 438 (type II)


		Size (approx):	72mm x 125mm x 20mm (max) (w,h,d) Weight 80g excluding batteries
		Power:	9.0V DC, 1 x PP3 size battery. It accepts an adaptor (9V DC 150mA) through a socket on the top side to the far right.
		Case:	Slim and slightly squeaky three-piece case made from smooth black and light grey plastic. The upper black section is raised (to accommodate the battery) and printed with white text for the brand and model number. Below this is a sloping red plastic display filter with more printed white text for the numerals. The display is bright enough but with limited viewing angle. A metallic panel serves as the keyboard surround with some black text for the on/off switch. The small keys are short travel with a loud click.
		Display:	8 digit red LED with individual bubble lens and no ninth digit
		Features:	Standard four function with percentages, sign change and four function memory
		Age:	1978
		Manufacturer:	Manufacturer is not mentioned, there is no country of origin. The serial number 814040 is on a sticker on the inside of the battery compartment
		Comments:	Cheap and cheerful calculator that has awful keys and a very limited viewing display (more than most LEDs). No information even in the manual as to where this was made - typical of the cut-throat boom years with minimum components. The original case is brown soft plastic with an open top. The logic is let down by seven digit negative numbers and the pseudo fixed decimal bug. This calculator is very similar to the earlier Sovrin 438 type1.

Components:	1 x cpu; Texas TMS0972NL KBPT 7806 (week 6 of 1978) 28 pin DIL, 0.6" width 1 x 8 digit LED display unit with individual bubble lens No other components
Boards:	The keyboard assembly is fixed to the front via four screws and the main cpu board (SPL 0062) sits loose on top, face down. The are joined by a 12-way ribbon cable.
Construction:	Held together by internal lugs only be careful not to damage this calculator if trying to open it. I found the best way was to lever the rear section away at the top and then progress down the sides. The rear section will then come away.

Logic comments:	The (CE) key is used to cancel an entry whilst (C) clears the whole calculator
	Input overflow is suppressed inputting an ninth digit is ignored
	Negative numbers are shown with a "-” in the immediate left hand digit but as there is no ninth digit to travel into you are limited to seven digit negative numbers
	There is an automatic constant on all four functions
	The change sign function can be used in mid number entry.
	Divide by zero shows a flashing “0.” in the far right (first) digit and is recoverable using (CE).
	Overflow shows the result flashing and is recoverable using (CE)
	There is no indication of memory storage - you have to remember it
	It suffers the pseudo fixed decimal bug: key in (1)(+)(0)(.)(0)(0)(0)(=) to give "1.000" which remains a three digit fixed decimal number until more digits are needed or multiply/divide is used

manual

The manual measures 115mm by 70mm and is 16 pages in black and red. In English only it gives quite a few examples and even has a section in the back for your own notes.