Toshiba BC-0804B

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Calculators: Desktop: Toshiba BC-0804B

		Size (approx):	104mm x 175mm x 42mm (max) (w,h,d) Weight 446g including rechargeable battery pack and strap, manual says 295g.
		Power:	7.5V (dry) 5 x AA sized batteries or 6.0V (Ni-Cd) internal (strange triangular shape) rechargeable battery pack (that was an option on purchase). It accepts an adapter/charger (BH-101 (in the US) or BH-103 in Europe) ) through a top side, three-pin, socket on the far left. Adapter can be used with dry cells in place. Charge time is quoted as 30-40 hours when in use or 15-20 hours when off. The battery compartment has a black ribbon to aid battery pack removal. It was also supplied with a disposable battery pack with orange ribbon pull. There is a "battery checker" meter at the top left of the calculator. The BH-103 charger is enormous - nearly half the size of the calculator and is rated 7.5V 150mA, 9V 45mA.
		Case:	The example pictured is very yellowed with long-term UV exposure. The case is made from a two-piece light grey, gloss plastic design with an additional central side black painted section. The top area contains a blue and black printed metallic sticker with the brand and model number that sits in its own raised recess. To the left of this an inset area contains a compass-like battery meter surrounded by matt black plastic. A even further inset section contains a switch with white printed text on smooth black plastic. The green plastic display filter is sloped and slightly inset. They keys are long travel, bouncy typewriter-like, with a soft metallic click surrounded by matt black plastic. Another inset areas contains a switch with another black printed metallic label. The top edge holds a sturdy metal tag for the black plastic carry strap.
		Display:	8 digit green VFD with a ninth digit for minus sign and error indicators
		Features:	Standard four function RPN logic. Switch for floating and fixed zero or two decimal points.
		Age:	1973
		Manufacturer:	Tokyo Shibaura Electric Co. Ltd., Japan. Serial number H69741.
		Comments:	Sturdy and heavy calculator that has obviously been well used in this example. Marvellously extravagant battery indicator makes this very attractive. The logic is appalling with every bug known to man and trailing zeros when division is used. The original case is soft black plastic with a top and right side zip and gap for the carry strap to get through. It is embossed with Toshiba on the front.

Components:	2 x cpu: Toshiba T3127 3G (date code July 1973), 28 pin DIL, 0.6" width white ceramic package Toshiba T3125 3H, 24 pin DIL, 0.6" width white ceramic package 3 x ICs: Toshiba TM4355P 3H, 16 pin DIL 0.3" width black plastic 1 x eight digit plus symbol cluster VFD unit, single tube round face: Toshiba E6518 3 x transistors 10 x diodes 8 x capacitors 23 x resistors 1 x resistor array 1 x transformer 1 x miniature power meter 1 x triangular Ni-Cd Battery pack Toshiba TN-5R450 6.0V 450mAh
Boards:	The keyboard assembly (Toshiba A-0131) sits loose on top of the main cpu board (Toshiba) and held rigid by the 22-way blue multi-way connector and a support pillar. Even then this is not enough connections as an additional 6 wires are needed for the switch. The keyboard is fabulous with individual magnets and reed switches which are intervened by the switched metal plate.
Construction:	Remove the two screws and their washers from the back and the front section will lift off easily.

Logic comments:	(CE) cancels an incorrect numerical entry, pressing a second time (C) clears the calculator
	Overflow on number input is not suppressed, typing in a nine digit number results in an overflow with "I-" displayed in the far left (ninth) digit which is not recoverable
	There is switched constant (with the K switch) for multiply and divide only
	It uses Reverse Polish Notation (RPN) logic: to calculate 4-6 key in (4)(+=)(6)(-) to give "-2"
	Negative numbers are shown with a "-" sign in the far left (ninth) digit thereby allowing full eight digit negative numbers.
	Overflow shows the result with "I-" displayed in the far left (ninth) digit which is not recoverable
	Divide by zero shows nothing but "I-" displayed in the far left (ninth) digit which is not recoverable
	The on/off switch also sets the Floating/zero or two decimal point mode
	It suffers the negative zero bug: key in (1)(+=)(2)(-) to give "-1" then add one by (1)(+=) to give "-0"
	It suffers the pseudo fixed decimal bug: key in (1)(+=)(0)(.)(0)(0)(0)(+=) to give "1.000" which remains a fixed three decimal point number until more digits are required
	It suffers the trailing zeros bug: key in (6)(/)(5)(+=) to give "1.2000000" which remains in this format. This will always happen when division is attempted.

Inside

The scan on the left shows the front and keyboard assembly removed. Typical of its early 1970s date there are five ICs, two main ones in white ceramic packaging.

At the top right you can see the wedge-shaped battery compartment whilst at the bottom you can see the blue block connector for the keyboard.

The ICs are made by Toshiba, as is the display and the board; as close as you get to vertical integration I guess.

manual

The manual measures 105mm by 149mm and is 24 blue and black pages. It is heavy gauge, high quality feeling paper. This example is in English only and has nine stickers covering mistakes or alterations on various pages. You would have thought it to be cheaper to just reprint it.

With plenty of examples, photographs and descriptions this is very good indeed.

Printed in Japan.

Quotes battery lifetimes as 3-4 hours for manganese, 5-6 hours for long-life manganese and 8-12 hours for alkaline batteries. 3-5 hours can be expected from the rechargeable batteries.