Casio 8U

		Home New Stuff Author Links Guest book Web-log	Adverts Bric-a-brac Calculators Components Ephemera Events	For Sale Glossary History Hit or Miss Radios Transport	Ultra Valves Wanted Metal Puzzles Caravan

Calculators: Desktop/Handheld: Casio 8U

		Size (approx):	115mm x 180mm x 50mm(max) (w,h,d) Weight 410g (excluding batteries)
		Power:	7.5V using 5 x AA sized batteries. It accepts an adapter (undefined but 7.5V 1W, centre negative) through a socket on the top side to the far left. The battery compartment has a red ribbon to aid battery removal. The on/off switch is on the left hand side, near the top.
		Case:	Large, wedge shaped case made from two pieces of stippled white plastic and a front section in matt black. The upper front has a plastic piece label painted silver that sits in its own recess with the brand and model number. The neutral plastic display filter is heavily tilted and inset so gives a bright clear image. It has white printed text for the numerals and overflow indicator. The keys are early desktop calculator in style with a long travel and hollow sounding strike. The two switch labels are a black printed metallic sticker that sits in its own bowed recess.
		Display:	8 digit blue VFD with a ninth "E" digit for error indication. Small "o" notation (see below).
		Features:	Standard four functions with switched decimal point and constant function. Semi-Reverse Polish Notation (RPN).
		Age:	1973
		Manufacturer:	Casio Computer Co., Ltd., made in Japan. A serial number is contained on a sticker on the inside of the battery compartment which is unreadable in my example.
		Comments:	Interesting early Casio that tries to bridge the gap between a desktop and handheld machine. As it will just fit in the hand, is battery powered and has a carry strap on the case it is probably best to call this a transportable. The original cover is white soft plastic with a top/side/bottom (with a little bit of the remaining side) zip and integrated carry strap. It has Casio embossed on the front and Made in Japan on the back. As you would expect, the RPN logic is archaic with lack of recovery. However, the pseudo fixed decimal bug is a surprise on a switched decimal calculator. This appears to be a clone of (or vice versa) the Sperry Remington 803C.

Components:	1 x cpu: Hitachi HD3276P 3E4 (date code May 1973), 28 pin DIL 0.6" width 1 x IC: Hitachi HD3124P 3C, 16 pin DIL 0.3" width 1 x IC: Hitachi HD3252P 3G3, 16 pin DIL 0.3" width 2 x IC: Toshiba TM4352P 3F, 16 pin DIL 0.3" width 1 x VFD unit: eight digit plus "E" single tube round face: Toshiba E6522 3H 7B 2F 3 x transistors 17 x diode 12 x capacitors 9 x resistors 6 x resistor arrays 1 x transformer unit: Fuji MCT0607 3F-15
Construction:	Remove the two screws from the back and the rear section will left off - being careful to hinge of the top two lugs without breaking them.
Boards:	The main cpu board (8J-1(A) ) sits loosely on top of the keyboard assembly, and is joined by a bunch of 14 coloured wires from a connecting block. The keyboard has four of its own capacitors.

Logic comments:	The (C) button is used to clear last entry of a number and the (AC) is used to clear the whole calculator.
	Overflow on number input is suppressed, typing in a nine digit number ignores the ninth digit.
	An overflow error shows zero result and an "E" in the far left (ninth) digit, negative or positive and is not recoverable.
	Divide by zero results in zero and an "E" in the far left (ninth) digit which is also not recoverable.
	There is switched constant on multiply and divide only
	The logic is Semi-RPN: to calculate 4-5 key in (4)(+=)(5)(-=) to give "-1"
	Negative numbers are flagged by a "-" sign in the far left (ninth) digit thereby allowing full eight digit negative numbers
	The decimal notation is switched between floating (F) and fixed 0,2 and 4 digits.
	It suffers from the pseudo fixed decimal bug: switch to floating mode (F) and key in (1)(+=)(0)(.)(0)(0)(0)(+=) to give "1.000" which will remain a three digit fixed decimal until more places are needed.

	The scan of the main board shows the high IC count typical of such an early calculator. Interesting to see the VFD with a dedicated "E" digit rather than the normal "8" on the far left. Notice also the use of a green block connector to the lower right. This connects the the keyboard and can be completely removed for servicing: no expense spared. The reference number of 8J-1A is also interesting and may make a link to the later "J" series desk-top calculators from Casio.
		The display is typical of many early Casio (as well as Sperry) calculators in that the zero is represented by a small "0" rather than a "0". It is believed that this format allowed for a segment (or a single segment driving circuit) to fail and still the individual numbers would be identifiable. It was not generally adopted after 1974. This is a representative image, the actual display has an extra mid horizontal segment used in the display of the number four.