Electronic Resources Memory Master X

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Calculators: Handheld: Electronic Resources Memory Master X

		Size (approx):	78mm x 156mm x 25mm (max) (w,h,d) Weight 124g excluding batteries
		Power:	4.5V DC using 3 x AA size batteries. It accepts an adaptor/charger (rear label states 3.3-4.65V, 200mW whilst the manual states 3.5-4.7V 20-150mA) through a socket on the top side to the far left. The on/off switch is on the left hand side just above the display. An adaptor can be used with the batteries in place. A charger can be used when the calculator is switched off.
		Case:	Made from a two-piece matt black plastic case that feels a little more solid than other Memory Masters. The top area is slightly thicker in order to accommodate the batteries. The red plastic display filter is flush and tilted and is printed with white text for the model name. The keyboard is surrounded by a brushed aluminium panel with black text for the marketing strap line. The small keys are short travel with a loud click type but work well on my example.
		Display:	8 digit red LED with individual bubble lens, and a ninth digit for negative and memory indicators.
		Features:	Standard four functions with percentages. register exchange, square root, squares, reciprocal, parenthesis, change sign and five function memory.
		Age:	1976
		Manufacturer:	No maker's name, no serial number, no model number, made in Hong Kong. The manual is credited to Electronic Resources Ltd, Hong Kong.
		Comments:	No-name calculator that boasts a better range of functions than most and is quite solidly built. However, the logic is slightly sloppy with negative square roots, the pseudo fixed decimal bug and single memory register that gets obliterated if you use the parenthesis function.

Components:	1 x cpu: Rockwell A5502PB 7550 (week 50 of 1975), 42 pin staggered DIL, 0.6" width black plastic with metal cap 1 x 9 digit red LED display unit 4 x transistors 3 x diodes 4 x capacitors 9 x resistors 1 x miniature potentiometer 1 x transformer
Boards:	The main board (751017A) is located on top of the keyboard assembly (PCB146159) and fixed by four screws into plastic posts and sturdy metal straps. The are joined by 16 soldered strong wires. The cpu board has a cut-out so that the potentiometer can be altered from the underneath.
Construction:	Remove the single screw from the rear. Then gently prize the edges apart to undo the internal poppers. The back will lift off. The keyboard area has four round cut-outs covered by the metal surround. Thus the case was used for other models.

Logic comments:	(C/CE) cancels an incorrect numerical entry, pressing a second time clears the calculator
	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 (ninth) digit thereby allowing full eight digit negative numbers
	Overflow shows the result with all decimal points alight and is recoverable using (C/CE)
	Divide by zero results in "0.0.0.0.0.0.0.0." and is recoverable using (C/CE)
	Memory store is indicated by the decimal point of the far left (ninth) digit
	You can clear the memory by using the ( "(" ) or the ( ")" ) keys as this function uses the memory to hold the temporary result
	The (M-X) key exchanges the memory with the display register
	You are allowed negative square roots which result in a negative number
	The change sign key can be used in mid entry of a number
	This calculator has the pseudo fixed decimal bug; key in (0)(.)(0)(0)(0)(+)(1)(=) and the answer will be "1.000". This fixed decimal mode remains for addition and subtraction until the result requires more precision.

The manual measures 117mm by 76mm and is 28 total pages. The cover is red and black whilst the (all English) internal pages are just black. Quite a good manual (grammar aside) with plenty of instructions and examples.

Electronic Resources Ltd, Hong Kong.

The manual states that the size of the calculator is 75mm x 140mm x 20-37mm which is obviously wrong compared with my (rougher) measurements listed above. The diagram of the calculator in the manual is obviously the correct one.

Notable quotes:
"The Memory Master is a pocket size junior slide rule, designed especially to fulfil the requirements of both the businessman and the students. [sic]"

"The calculator is automatically cleared when the power is turned ON (allow 0.5 second rest time after turning OFF before turning ON again)"