Caltronic 606

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Calculators: Handheld: Caltronic 606

		Size (approx):	83mm x 154mm x 25mm (w,h,d) Weight 170g excluding batteries
		Power:	9V DC, 1 x PP3 size battery. Also accepts adapter through top side socket on the left.
		Case:	Brick shaped two piece black plastic case with stuck on aluminium panels on the front and sides. Concave (horizontally only) keys have adhesive plastic labels - never going to be reliable. The "5" appears wrongly placed. The keyboard is a sealed unit so I could not rotate it without a lot of de-soldering - which has never been done. Either this is an escaped reject or it was supposed to be like that. Maybe the user put them on at purchase time and did it wrong. Logo is painted on in a dot-matrix style font and survived well. First switch is on/off, second is choice between 2 decimal points or none. Fabulous!
		Display:	6 digit red LED with bubble lens
		Features:	Basic four function with percentages.
		Age:	1973 - very early LED pocket calculator
		Manufacturer:	No manufacturers' name. Serial No. 137132, Made in Hong Kong.
		Comments:	Judging by the date code on the cpu, the 6-digit LED and the "up to two" decimals this is a very early LED model. The left arrow key allows you to see up to 13 digit answers by "switch-over" to the 6 most significant digits. I would like to know more about this one - so if anyone can help? Two or none decimal switch is also unusual. Buttons are hollow sounding put positive enough.

Components:	1 x cpu, Mostek MK5012P 7252 (week 52 of 1972?) in 40 pin DIL 2 x 3 digit bubble lens LED display 22 x transistors 28 x diodes 51 x resistors 14 capacitors
Boards:	The main board is fixed by four screws (which also go through the keyboard's board). The display is attached via an array of strong wires and a further two screws. The keyboard assembly is also attached via string array of "U" shaped wires. The only ID on the main board is "613A", whilst the keyboard PCB has "Ramsgate Inc, Eveleth, Minn. USA, MKR 102C".
Construction:	Opened by undoing two screws at the back, the whole back half lifts easily off. The keyboard assembly is a sealed unit soldered onto a board.

Logic comments:	There is no way to cancel entry, only clear the calculator by use of (C)
	The really neat (left arrow) key allows you to see up to a 12 digit answer by shifting the most significant bits
	Input overflow is caused by inputting the 13th digit; display will show "0.0.0.0.0.0." - it is not recoverable.
	My model never actually shows a negative sign!
	In two decimal point mode there is no trailing zero suppression, the display will start with "0.00"