Intercord Electronic 101

		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 Clocks

Calculators: Handheld: Intercord electronic 101

		Size (approx):	78mm x 134mm x 23mm (max) (w,h,d) Weight 122g excluding batteries and carry strap
		Power:	3.0V DC using 2 x AA size batteries. It accepts an adapter (3V DC 0.4W, 0.11A centre negative) through a socket on the top side to the far right. Unusually the battery compartment is accessed by removing the front upper panel.
		Case:	Two piece case in glossy orange and matt black plastic. The upper section (which is the battery compartment cover) is printed with black text for the brand and model number. The small neutral plastic display filter sits flush and flat with white printed text underneath for the indicator description. The small round keys are medium travel with a soft click. There is a small plastic lug to the upper left hand side for a carry strap.
		Display:	8 digit blue VFD with a ninth digit for negative and error indication. Display is left leading rather than today’s standard right reading.
		Features:	Standard four functions with percentages, square root, change sign and switched floating/financial input mode.
		Age:	1975
		Manufacturer:	Intercord, no manufacture, made in Japan, serial number 6013770Y is on a sticker inside the battery compartment
		Comments:	Classic 1970s orange colour that must have gone well with contemporary furniture and wallpaper! Looks like a US brand version of an Omron calculator such as the Omron 86. As with most of the Omron/Hitachi chips of this era, the logic is pretty poor with no recovery and several problems like the negative zero bug. My example had poor key response. On examination I was amazed to see that connectors to the keyboard have never been soldered! This may have been a factory reject or just lucky that it once worked.

Components:	1 x cpu: Omron (actually an Hitachi) HD36291 5C33 (March 1975), 28 pin DIL, 0.6" width black plastic 1 x 9 digit VFD unit: single glass tube round face 2 x transistors 6 x diodes 7 x capacitors 3 x resistors 2 x resistor arrays 1 x transformer
Boards:	The keyboard assembly is attached to the front with seven screws. It joins to the main cpu board (87-3404 02A) via 12 brass(?) wide wires. This main board is held to the rear section with two sturdy plastic lugs.
Construction:	Remove the long screw from the rear of the case. Carefully pop the side lugs and hinge off the front at the bottom edge. On opening you will see that the battery compartment is then a lightly fixed black plastic unit.

Logic comments:	The (C/CE) key is used to once to clear the last entry and a second time clears the whole calculator
	Input overflow is suppressed, typing in a ninth digit is ignored
	There is automatic constant on multiply and divide only
	Negative numbers are indicated by a “-“ in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	Overflow shows the result and “C” (“E” if negative) in the far left (ninth) digit and is not recoverable
	Divide by zero shows zero and "C" in the far left (ninth) digit and is not recoverable
	Negative square roots are not allowed and show the result and “E” in the far left (ninth) digit and is not recoverable
	Change sign can be used in mid number entry but not before
	The A/M switch can be used to change the input from Accounting (normal) and Money where keying in (1)(2)(3) results in the number “1.23”
	It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1" now (+)(1)(=) to give "-0"
	It suffers the divide to negative zero bug: key in (1)(+/-)(/)(1)(0)(=)(=)(=) etc. to eventually give "-0"