Toshiba BC-0808B

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Calculators: Handheld: Toshiba BC-0808B (experimental new super-info page)

		Size (approx):	97mm x 148mm x 30mm (max) (w,h,d) Weight 220g excluding batteries but including strap
		Power:	6V DC, 4 x AA size batteries. Accepts an adaptor (Use BH104 and BH105 only, 6V 750mW) through a socket on the top side on the far left. The battery compartment has a black ribbon pull to help remove batteries.
		Case:	Two-piece main case of smooth light grey plastic. There is also a middle section of spray-painted black smooth plastic and two black plastic ridged end panels. The oversized neutral plastic display filter is flat but raised. Within this is a recess that holds a black printed metallic sticker with the brand name and model number. There is a sturdy claps on the top left side to cater for a black plastic carry strap, They keyboard surround is raised black plastic panel with a prominent ridged design. The keys are soft and squishy with a soft click. The on/off switch sits in its own recess with a silver printed bronze coloured sticker.
		Display:	8 digit blue VFD with a ninth digit for negative and error indicators
		Features:	Standard four functions
		Age:	1974
		Manufacturer:	Toshiba Electronic Calculator, Tokyo Shibaura Electric Co. Ltd. Japan, serial number F85697.
		Comments:	Bulky and sturdy calculator which only just fits in the hand but has a large bright display. The logic is very poor with no recovery, loads of bugs and no trailing zero suppression on division. Not much more you could get wrong on a four-function calculator! A quirky early calculator for your collection.

Components:	1 x cpu: Toshiba T3241 4E (date code May 1974), 28 pin DIL 0.6" width white ceramic with metal cap 1 x IC: Toshiba TM4356P 3-L (date code November 1973), 20 pin DIL 0.3" width black plastic, VFD grid driver 1 x 9 digit VFD display unit, E6523 single tube round face 2 x transistors 8 x diodes 9 x capacitors 3 x resistor arrays 13 x resistors 1 x transformer
Boards:	The keyboard assembly (A030 4601620) sits lose on the battery compartment and is joined to the main cpu (ref: 4462141003) board by a soldered 15-way block connector.
Construction:	Remove the single screw from the back and the whole front of the case lifts off easily (see below).

Logic comments:	(CE) is used to cancel the last number entered and (C) to clear the whole calculator.
	There is automatic constant on multiply and divide only
	Input overflow is not suppressed, inputting a ninth digit causes an overflow which is not recoverable
	Overflow shows the result and "E" in the far left (ninth) digit and is not recoverable
	Divide by zero shows just "E" in the far left (ninth) digit and is not recoverable
	Negative numbers are shown with a "-" in the far left (ninth) digit thereby allowing full eight digit negative numbers
	It suffers the negative zero bug, key in (-)(1) to show "-1" then (+)(1) will give "-0"
	It suffers the extended divide to negative zero bug, key in (-)(1)(/)(1)(0)(=)(=) etc... to eventually show "-0.0000000"
	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 or use divide.
	There is a low battery warning: the top right hand vertical segment of the ninth (far left) digit will light when voltage drops below 3.6V
	Oddly enough, all results of a divide calculation are seven digit decimals, i.e. (1)(0)(/)(2)(=) gives "5.0000000"

The image (left) shows the front of the case removed. Notice the early (1974) white ceramic packed Toshiba main cpu IC. Lots of components, vertically mounted as there is so much space in the large case. Obviously manually assembled with plenty of printed text for the component guides.

The image (right) shows the original PCB design layout. The Ref. No. on this plot is one digit earlier: 4462141002. I'll leave you to play "spot the difference" (hint the capacitor to the immediate left of the LSI IC is one thing).

How to Detach the cover assembly

(1) Remove one screw located around the backward portion at the rear of the base.

(2) Lift up the cover in the direction indicated by the arrow and take off the cover from the hanger portion of the base.

Notes: The cover must be taken off from the base while holding down the keyboard since it maybe sometimes dragged out together with the cover.

How to detach PWB general Assembly

(1) Separate the 2P-connector cord of an AC adaptor if the former is inserted into the latter

(2) Separate the 2P-F-socket from the rib of the base

(3) Draw out the PWB general assembly with caution for the output terminal of the battery.

(4) Disconnect the lead wire soldered to the output terminal of the battery by using a soldering iron to remove the PWB general assembly from the base

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Service manuals available: Toshiba BC0808B