Sharp EL-801 Elsimini

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Calculators: Handheld: Sharp EL-801 (Elsi mini)

	Size (approx):	73mm x 105.5mm x 27mm (max) (w x h x d) Weight 172g not including batteries but including strap.
	Power:	6.0V DC using 4 x AA size batteries, 0.5W. It does not accept an adapter. The on/off switch on the left hand side is a press-and-slide type which is not very common.
	Case:	The two-piece case in smooth black plastic is practically completely spray painted silver with a black edging on the sides. An upper unpainted panel has silver printed raised text for the brand name. The purple display filter is flush and flat with the letters K (for constant) and B (for battery level) printed in white. The display is clear, not too bright but has a wide angle of view. The keys are quite squishy, rock about a bit but work well. The battery compartment comes fully out from the bottom of the calculator by pushing in tow side lugs. There is a metal tag for a carry strap on the top - much better than the plastic ones you normally get. The top side panel has a large metallic sticker with the normal details of origin.
	Display:	8 digit red LED (flat dot type) with an extra horizontal bar on the far right. There are two separate red LEDs for constant and low battery indication.
	Features:	Standard four functions and constant, RPN logic.
	Age:	c1972 - one of the very first pocket calculators
	Manufacturer:	Sharp Corporation, made in Japan. Serial number 207424X.
	Comments:	Very early compact and solid feeling calculator with the best type of LED display. I never did understand the battery indicator idea - just as you batteries are running low then an extra LED lights up to drain them even more! Archaic logic with negative zero, pseudo fixed decimal and trailing zero bugs make it annoying to use but an early classic compact calculator all them same. The strap can be put through a gap in the top. Very similar is shape and design to the Prinztronic Micro. Inside is marvellous; extreme high density components and connecting blocks to take the whole thing apart - wow!

Components:	1 x cpu: Toshiba T3103, 28 pin DIL, 0.6" width 1 x IC: Toshiba T1271, 16 pin DIL, 0.3" width 8 x 1 digit red flat LED seven segment units with no lens 1 x red LED horizontal unit 2 x individual red LEDs 12 x transistors 7 x diodes 3 x capacitors 35 x resistors 1 x variable resistor
Boards:	The primary cpu board (4073PWB-A) is attached to the display board (4083PWB-A) via a 26-way block connector and is connected to the keyboard assembly by another 13-way block connector. This modular system allows a higher "stacked" density as well as making servicing very easy.
Construction:	Undo the screw on the top side and the rear of teh calculator will easily lift off.

Logic comments:	The (C) key is used to clear the calculator there is no cancel entry function
	Input overflow is not suppressed inputting a ninth digit results in all eight decimal points alight and is not recoverable
	Negative numbers are shown with a "-" to the far right of the digits thereby allowing full eight digit negative numbers
	There is selectable constant on multiply and divide by pressing the (K) key. An LED lights up by the letter K to remind you.
	Divide by zero shows "........" and is not recoverable
	Overflow shows "........" and is not recoverable
	Interestingly, the results of a division do not have trailing zero suppression; key in (9)(/)(5) and you get "1.8000000" which continues into the next calculations.
	The logic is reverse polish notation so takes a bit of getting used to; to work out 9-5 key in (9)(+=)(5)(-=) which shows "4".
	This calculator suffers the negative zero bug. Key in (1)(+=)(2)(-=) to give “-1” the add one by (1)(+=) to give “-0”
	This calculator suffers the pseudo fixed decimal bug; key in (1)(+=)(0)(.)(0)(0)(0)(+=) and the display will show “1.000” which will remain until a calculation causes it to be exceeded.

	This scan shows the primary cpu board with the green connector blocks at the bottom to the display board and keyboard assembly. The ceramic encapsulated Toshiba IC and secondary support IC is a sure sign that it is early 1970s. By vertically mounting the components, and stacking the two boards on top of each other they achieved an amazing density of components for the time. The on/off switch is hard-wired to the left of the board.
	The secondary display board clearly shows the digits with the extra "minus sign" display unit to the right. Also note the two small pin-point LEDS to the top left and top right. A transistor driver for each digit also indicates the early 1970s date. The rivet and metal tags on the bottom left are the battery unit connectors.