Hardy 8MS

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Calculators: Handheld: Hardy 8MS

		Size (approx):	74mm x 130mm x 25-35mm (w,h,d) Weight 110g excluding batteries
		Power:	7.5V, 5 x AA size batteries. It accepts an adapter/charger (undefined) through a socket on the right side to the far top.
		Case:	The body is made from a two-piece white and light brown plastic case with the top gently sloping up in a curve. The green plastic display filter is inset and titled for desktop viewing. This filter is printed with white text for the digit numbers and sign indicator. The black plastic keyboard surround has raised boxes not unlike a Commodore. In fact this matches the Commodore-like keys and colour scheme. Just above the keys sits a brushed aluminium panel, printed with black text for the on/off switch label and the brand and model number. The keys are soft, spring and short travel and on my example the lower ones are a little unreliable.
		Display:	8 digit green VFD, with an additional ninth digit for negative and memory indication.
		Features:	Standard four functions with percentages, change sign, register exchange, square root and four function memory
		Age:	1975
		Manufacturer:	No information on the calculator other than Hardy Electronic calculator, no serial number either.
		Comments:	Quite well made mystery calculator. The five batteries are odd and consume the vast majority of space inside the case. Could this be a Commodore factory clone? The original case is soft black plastic with flip over top flap and front tuck in section. It has a belt clip at the back for mobile calculating. The logic is sound with good recovery and only let down by the pseudo fixed decimal bug.

Components:	1 x cpu: Rockwell A5901PA 7536 (week 36 of 1975), 42 pin staggered DIL, 0.6" width 1 x 9 digit VFD: flat face single tube; Futaba 9-ST-12 5G (July 1975) 1 x diode 4 x capacitors 19 x resistors 1 x sealed transformer block
Boards:	One single board for cpu components and keyboard assembly (L59AG-B Designer Miss Y. D. Yang Lyceum Labs Aug '75). This board is held in place by two plastic side lugs whilst the key assembly by 11 screws.
Construction:	Remove the single screw from the back and the rear of the case will easily lift off, hinging from the bottom.

Logic comments:	(CL) is used once to clear the last number entered whilst a second press will clear the calculator
	Input overflow is suppressed, keying in a nine digit number ignores the ninth digit
	Negative numbers are represented by a “-“ in the far left (ninth) digit thereby allowing full eight digit negative numbers
	Overflow shows the result and all decimal points alight and is recoverable using (CL)
	Divide by zero shows “0.0.0.0.0.0.0.0.” and is recoverable using (CL)
	There is automatic constant on all four functions
	Change sign can be used in mid number entry
	The (Y-X) key exchanges the previous and current registers
	Memory store is indicated by the far left (ninth) digit’s decimal point alight
	It suffers from the pseudo fixed decimal bug: key in (1)(-)(0)(.)(0)(0)(0)(=) and you get 1.000 which will remain as a fixed three digit decimal number until a multiply or divide causes otherwise.

The scan on the left shows the calculator with the rear removed. Unusually there is just one double-sided board for the keys and the cpu. This had to be done as the large battery compartment takes up most of the volume inside the case.

Very unusual to see a hand-written note etched on the bottom area:

L59AG-B
Designer Miss Y. D. Yang
Lyceum Labs Aug '75"

Pull out the assembly and this is the view from the front with the keyboard still attached. Not much in the way of components; a stack of resistors and a few other bits.