Texet L-0831 (type II)

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Calculators: Handheld: Texet L-0831 (type II)

		Size (approx):	68mm x 125mm x 17-22mm (w,h,d) Weight 76g excluding batteries
		Power:	9.0V DC, 1 x PP3 size battery. Accepts an adapter (undefined) through a socket on the top side to the far right. A warning on the back states that the battery must be removed before using and adapter. It has a power save function.
		Case:	The main case is made from two pieces of smooth black plastic with a prominent raised upper area to accommodate the battery. An oversized red plastic display filter sits flush, is heavily angled and gives a reasonably bright display with limited angle of view. This filter has raised lettering which is painted silver. The keyboard surround has white printed text for the key and switch labels. The small keys are short travel with a positive click which rattles when shaken.
		Display:	8 digit red LED with individual bubble lens with a ninth digit for negative and error indication
		Features:	Basic four function with percentages, selectable constant and two-function memory. Display power save recovery.
		Age:	1976
		Manufacturer:	No manufacturer details, made in Singapore, serial number 195606 - I think
		Comments:	Cheap and cheerful calculator that is quite attractive due to the shaped large display filter. The logic is very poor with confusing constant system, no recovery, negative zero bugs and basic memory. This calculator is very similar to the Texet L-0331T (type I). It is also similar to some Adman and others that can be seen on Same Calculator.

Components:	1 x cpu: National Semiconductor NS 607 MM5738N (date code week 07 of 1976) 24 pin DIL, 0.6" width black plastic 1 x IC (display driver?) unmarked, 22 pin DIL, 0.3" width black plastic 1 x 9 digit bubble lens LED; HP 74414751 0 x transistors 1 x diode 0 x capacitors 0 x resistors
Boards:	The single cpu board (WU xxx831) sits above the keyboard assembly.
Construction:	Difficult this one - be careful! Gently prize the back of with a blunt (wooden) instrument whilst squeezing the front in. Start with the lower edge. The back will pop off. It is very easy to damage so if in doubt - don't do it.

Logic comments:	The (C/CE) key is used to clear the last number entered and a second press clears the whole calculator
	Overflow on the input of a number is suppressed, keying in a ninth digit is ignored
	There is selectable constant with a temporary register. Key in (8)(X)(3)(=) to give "24", now three is stored in the constant register so (5)(X)(K=) will give "15"
	The negative number is shown by a “-“ sign to the immediate left of a number travelling into the ninth thereby allowing full eight digit negative numbers
	An overflow shows the result and "E" in the far left (ninth) digit and is not recoverable
	A divide by zero results in "E00000000" and is not recoverable
	Memory store is not indicated - you have to remember it. by an upper "^r" in the far left (ninth) digit
	Use (MS) to store in memory and (MR) to recall, there is no memory clear, store zero.
	There is a power save function when the display switches to a single first digit only after about thirty seconds. Use the (D) key to recover. If you are displaying a single digit number, there is no way of telling if it's in power save mode.
	The percentage keys divides by 100, even in isolation and used repeatedly will result in an underflow error which is not recoverable
	It suffers from the negative zero bug: key in (1)(-)(2)(=) to give "-1" then (+)(1)(=) will give "-0". It also suffers the divide to negative zero bug

	Compare this with the Texet L-0831 (type I) inside case shot. Resize the new window for best comparison - please close this new window after use.
The image above shows the calculator with the rear of the case removed. Only a few extra components: a diode across the power supply to stop you plugging in the wrong polarity adapter. The board is attached to the front by melted plastic posts - about as cheap as you can make it - typical of this date.	The box to the right measures 68mm by 128mm and is 23mm deep - so is just big enough for the calculator. It is a double tuck-end box printed pink and silver.