The Hanimex BCM30 calculator, manufactured in Hong Kong in 1976, is a compact device designed for basic arithmetic operations. With dimensions of approximately 74mm in width, 132mm in height, and 21mm in depth, it weighs a light 90 grams, excluding batteries. The calculator is powered by a 9.0V DC PP3 size battery, with an option for an adapter through a socket on the top side.
The Hanimex BCM30 features a two-piece matte brown plastic case, designed to accommodate a nine-volt battery. The top section includes a slightly recessed brushed aluminum panel with black printed text indicating the brand and model number. A shaped red plastic display filter is sloped within its own escutcheon, providing a bright display but with limited viewing angles. The keyboard surround is made of beige smooth plastic, with an embossed “on” label for the switch. The keys are short travel with a pronounced click, typical of the 70s, in orange and dark brown colors.
The display is an 8-digit red LED with individual bubble lenses, lacking a ninth digit. The calculator offers standard four-function capabilities, including percentages, change sign, and four-function memory.
The components of the Hanimex BCM30 include:
- 1 x IC: Texas ZA0571 KFR 7620 (week 20 of 1976), 28 pin DIL, 0.4″ width black plastic.
- 1 x 8-digit red LED module: National Semiconductor NSA1188 624.
- 2 x capacitors.
- 3 x resistors.
The main circuit board sits face up on top of the keyboard assembly and is held in place by four plastic clips. Connection to the keyboard is via a 15-way collection of wires held by a small plastic former. Disassembly is challenging due to internal lugs and tight-fitting sides, which may result in damage.
Logic
- (CE) cancels the last number entered while (C) clears the entire calculator.
- 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 immediate left digit, but the lack of a ninth digit means only seven-digit negative numbers are displayed. Eight-digit negative numbers are allowed but not indicated as negative.
- Overflow shows the result flashing and is recoverable using (CE).
- Divide by zero shows zero flashing and is recoverable using (CE).
- Memory store is not indicated.
- Overflow in memory flags the error and zeros the memory.
- Change sign can be used in mid-number entry and before.
- It suffers the pseudo fixed decimal bug: key in (1)(+)(.)(0)(0)(0)(=) to give “1.000,” which remains a three-digit fixed decimal number until more digits are needed or multiply or divide is used.
The Hanimex BCM30 calculator is a straightforward device with a 70s color scheme and basic functionality. Its logic has some limitations, such as the lack of a ninth digit and memory indicator, memory loss on overflow, and a pseudo fixed decimal bug. Otherwise, it’s an interesting , collectible calculator.
