Binatone Junior Slide Rule

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Calculators: Handheld: Binatone Junior Slide Rule


		Size (actual):	80.5mm(max) x 150.5mm x 34.0mm(max) (w,h,d) Weight 148g excluding batteries.
		Power:	4.5V DC, 3 x AA size batteries. Also accepts adaptor (4.5V DC, 80mA, centre positive) through a socket on the right side, midway down. The batteries are held in a slot-in cartridge which is quite difficult to remove. It connects to two metal lugs.
		Case:	Two piece smooth black plastic case. At the top of the front is a raised green plastic filter that sits in a recess and has white printed text for the logo and model name. It gives a clear and bright display. Below this, the keyboard surround (with a matt pattern) has a grooved surround. Above the keys is a black panel (in its own further recess) with silver printed text for the on/off switch and some handy conversion constants. It is covered by a thin film giving a gloss effect. The keys are short travel with a soft feeling and very like some Commodore designs. A brief sticker on the back gives some calculation examples.
		Display:	8 digit green VFD with a ninth digit for negative, memory and error indication.
		Features:	Basic four function with percentages, change sign, square root, square, reciprocal, register exchange, parenthesis and five-function memory.
		Age:	1976
		Manufacturer:	Undefined, no country of origin, no serial number which is not uncommon for this brand
		Comments:	Sturdy enough calculator with a bright display. The logic is let down by the negative square roots and pseudo fixed decimal bugs, but there are some useful functions. The original soft black plastic case has a flip over top which tucks into the front section. I suspect that the keyboard assembly was sourced from the same place as Commodore used, as the reference numbers are similar.

Components:	1 x IC: Rockwell A5501CB 7617 (week 17 of 1976), 42 pin staggered DIL, 0.6" width black ceramic with metal round plate seal 1 x 9 digit VFD module, single glass tube flat face: Futaba 9-ST-10 6A (January 1976) 2 x transistors 5 x diodes 5 x capacitors 6 x resistors 2 x resistor arrays 1 x transformer: TDK SR-5 Japan
Boards:	The main cpu board (SR-55-A3) sits loose on the rear section with a piece of card to insulate it from the keyboard assembly (SR40 CEC-640830 KB-30-2) below. The keyboard is fixed to the front with numerous screws. The two are joined together by 15 strong wide wires.
Construction:	Remove the screw from the rear. This does not help a lot as the case is held together by internal lugs. Start by levering out the front section (from behind) up the side without the adaptor socket. To pop the top edge pock a blunt soft instrument through a hols in the battery compartment whilst twisting the case slightly. Then the most difficult edge (with the socket) can be gently levered away by pushing in the lugs - not easy and damage could result.

Logic comments:	(C) cancels the last number entered whilst a second press will clear the whole calculator, so it's a (CE/C) key really
	Input overflow is suppressed; inputting a ninth digit is ignored
	There is automatic constant on all four functions
	Negative numbers are represented by a "-" sign in the far left (ninth) digit thereby allowing full eight digit negative numbers
	Overflow shows the result and all decimal points on and is recoverable using (C)
	Divide by zero results in "0.0.0.0.0.0.0.0." and is recoverable using (C)
	Memory store is indicated by the decimal point of the far left (ninth) digit
	To add to the memory use (+M), to recall use (MT), to cancel use (MT)(MT)
	The change sign function can be used in mid number entry or before
	Negative square roots are allowed and result in a negative number
	Overflow in memory is flagged in the overflow way and retains the original number
	It suffers the pseudo fixed decimal bug: key in (1)(+)(.)(0)(0)(0)(=) to give "1.000" which remains a fixed three digit decimal number until you need more digits or use multiply or divide

This scan of the inside gives a good example of how the boards look in 1976. Unusual staggered pin configuration for the Rockwell IC.

But the usual array of components mostly orientated to provide the VF display with the voltages needed to run.

The two metal clips near the top are the battery cartridge connectors.

The manual measures 120mm x 75mm and is printed in one colour, black throughout. It has 12 total printed pages all in English with many good examples of calculations. It is a fan-fold construction - so gives one very long strip of paper.