Texet 1800

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Calculators: Handheld: Texet 1800

		Size (approx):	75mm x 135mm x19mm (w x h x d) Weight 92g excluding batteries.
		Power:	3.0V DC using 2 x AA size batteries. Can accept an adapter/charger (undefined) through a socket on the top side to the far left.
		Case:	Two piece cream (originally white?) and dark brown smooth plastic. Two recessed panels contain brushed aluminium plates around the keyboard and top section. The latter has printed black text with the make and model number. Very slightly tilted and flush neutral plastic filter gives a bright display with wide angle of view. The on/off switch does not have a label on my example – it looks like it never did(?). The keys are short-travel squishy type and work well. They look like Casio type keys with their individual plastic escutcheons.
		Display:	8 digit blue VFD with a ninth digit for memory, negative and error indication.
		Features:	Standard four functions with percentages, square root and four-function memory.
		Age:	1980
		Manufacturer:	Manufactured in Korea for Texet. There is no serial number that I can find.
		Comments:	Confusingly there appears to be another brown plastic Texet 1800 model! This example, however, is one of the better-built Texet calculators. In fact it is remarkably like a Casio in design and feel – good copy! The logic is sound but lack of error recovery and negative square roots are annoying. The original case is soft black plastic with open top. Exactly the same as the Brinlock 806MD.

Components:	1 x cpu: NEC D1803C E02169, 28 pin DIL 0.6" width 1 x 9 digit VFD unit, single glass tube flat faced; Futaba 9-ST-11, made in Korea. 2 x transistors 5 x diodes 2 x resistors 0 x resistor arrays 4 x capacitors 1 x transformer module
Boards:	The keyboard assembly is fixed to the front via 9 screws and to the main board that sits on top by a 15-way ribbon cable. The display on the main board wedges it in. Main board ref DH-8803.
Construction:	Remove the small screw on rear. Separate from the bottom and gently pop in the two small side lugs and hinge off the top two. The rear section will then come away.

Logic comments:	The (C/CE) key is used once to clear the last entry whilst a second press clears the whole calculator.
	Input overflow is suppressed, keying 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 results in “C” in the far left (ninth) digit and is not recoverable.
	Negative square roots are not allowed and result in “C” which is not recoverable.
	Memory storage is indicated by the far left (ninth) digit’s decimal point