Casio J-1

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Calculators: Handheld: Casio J-1 (aka J-811)

		Size (approx):	98mm (max) x 159mm x 25mm (max) (w,h,d) Weight 152g excluding batteries
		Power:	3V DC, 2 x AA size battery, 0.25W. Also accepts adaptor AD-2S through top side socket on the left.
		Case:	Large desk-top sized calculator that just about fits in the hand. Two-piece cream and very dark brown smooth plastic case. Large brushed aluminium keyboard surround printed with black text. Large square keys with typical Casio black plastic escutcheons. They are squishy but work very well. Slightly titled neutral display filter gives a clear display. Raised panel has silver printed logo and name and has survived well on this example. On/off switch has a printed green indicator. There are two other switches for floating/round down/round and 4/2/0 decimal places.
		Display:	8 digit green VFD (ninth digit is there but is never used)
		Features:	Basic four function with percentages, sign change, square root, and three function memory. Switches for fixed decimal point and round-up protocol.
		Age:	1978
		Manufacturer:	Casio Computer Company Ltd. Made in Japan. Ref J-811. Serial number 4423851 on sticker inside the battery compartment. Also had 4968275.
		Comments:	An oversized version of the Casio design to make a useful transportable desktop. However, the seven digit negative numbers and logic errors let it down - what a load of rubbish! Original black leatherette case has an open top and "Casio" embossed on the front and "Made in Japan" on the back. Very similar in design to the Casio J3.

Components:	1 x cpu: NEC D1877C E87236 (I think this is the 15 Dec 1978) 36 pin DIL, 0.6" width 1 x display: 9 digit single flat glass tube; NEC LD8191 TUBE NO. 8B Japan 1 x transistor 7 x diodes 11 x capacitors 3 x resistors 1 x transformer; TC-12 8?8 TDK
Boards:	Keyboard board is secured to the front via 5 screws and four plastic lugs. It connects to the main cpu board (Ref. F8Z-1B) via 21 stiff copper wires with an insulating strip. There is also a ground wire to a large shield panel stuck to the back.
Construction:	Remove the two screws from the back and then what! Not for the faint hearted this one. You need to squeeze in the upper case side which is practically impossible as it is so stiff. When the lugs are popped hinge off from the bottom. It took me 15 minutes. If you do not want to damage your calculator I would recommend you do not open it.

Logic comments:	The (C) button is used once to clear entry of a number, the (AC) is All-clear.
	Overflow on number input is suppressed
	Divide by zero just shows "E." and is not recoverable
	Overflow error is flagged by "E." in the first digit whilst displaying as near as you can to the result. Error is not recoverable.
	Storing in the memory using the (M+) or (M-) keys is not backed up by indication of memory store - you have to remember it! (AC) clears the memory!
	There is automatic constant all operators by pressing them twice. i.e. press (5) (x) (x) (2) (=) gives 10, (3) (=) gives 15.
	Sign change cannot be used in mid-number entry - it resets the number entry!
	This calculator allows the square root of a negative number with no error
	Negative numbers are flagged by a "-" sign in the leading left hand digit thereby limiting negative numbers to seven digits.
	If your press change sign on an eight digit number (that is the result of a calculation, not input) and has decimal points more than zero), it is changed to a seven digit number which is not recoverable.