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Sony SOBAX ICC-500W Electronic Calculator

Updated 6/29/2015

Sony. The name immediately brings to mind all of the wonderful electronics technology that we've come to take for granted...handheld transistor radios, the WalkMan, DiscMan, PLAYStation, and all manner of high-quality, high-technology, uniquely packaged consumer electronics. Sony's entry into the world of transistorized electronics came to be mostly because the company was the first Japanese company to license transistor technology from Bell Labs. This gave Sony the unique ability to produce their own transistors, which paved the way for Sony to produce many different types of innovative consumer products. One product that doesn't generally come to mind when the name Sony is mentioned is electronic calculators. Sony began participating in the rapidly growing electronic calculator marketplace in 1967, though they'd been developing electronic calculating machines in their research and development labs beginning as early as 1962, and started showing prototype versions of their calculator designs in early 1964. In fact, Sony showed a prototype machine called the MD-5 at an exposition at the World's Fair (New York City) in March, 1964, the same exposition where Sharp introduced their first electronic calculator, the Compet 10. The Sony prototype machine was in many ways technologically superior to Sharp's machine, with a 10-key design versus the full keyboard of the Compet 10, and was significantly more compact and lightweight than Sharp's machine. However, Sony didn't seize the opportunity to immediately make the prototypes into commercially viable reality. It took Sony almost three years, and a number of succeedingly more complex prototype calculators (MD-6, MM-7, and others, ending with the MX-11, which was the prototype machine behind the ICC-500W), before the company decided to attack the market with their designs, by which time the other early entrants to the market had established a solid head-start. The ICC-500W, the first of Sony's commercial electronic calculators, was finally introduced to the marketplace in June of 1967.

Prototype Sony MD-6 Calculator
Image Courtesy of the National Museum of American History, Kenneth E. Behring Center

It's interesting to note that Sharp is a major player in today's calculator market, while Sony is no longer in the market. It just goes to show that superior technology doesn't always win in the marketplace. Sony didn't really know how to market their technologically advanced calculators, while Sharp had very clearly defined market strategy and tactics. Sony high-level management was always somewhat skeptical of the consumer viability of electronic calculators, and while they begrudgingly agreed to support a calculator development project, the calculator division really never had all the support it needed to be successful. After remaining in the calculator market until 1973, Sony management realized that the margins on calculator products were diminishing, and the competition in the marketplace had become extremely high. As a result of these pressures, the decision was made to leave the market, and focus the technical resources of the calculator team in other areas.

The SOBAX (which is a name coined from the phrase "Solid State Abacus") line of electronic calculators were Sony's idea of what an electronic calculator should be if done the "Sony Way". And, true to Sony form, the machine is built like a tank, and performs like a Ferrari. The machine is built on a beefy all-aluminum and metal chassis. Sony was ahead of their time in terms of building a chassis that prevents the escape of radio frequency(RF) emanations from the machine. The chassis completely surrounds all of the electronics, providing an effective RF shield. The molded plastic case is secured by one fastener! Loosening this single captive fastener allows the lower half of the case to be removed. To remove the upper half of the case, a slide latch on each side of the chassis can be activated, freeing the upper half of the case. The power supply makes up the back section of the chassis, and while it is tethered to the rest of the electronics by a ribbon cable, it is on slides. Once two retaining pins are removed, and tension taken off of clips that retain the power supply module, the power supply can be slid out of the chassis. There's enough extra length in the power supply ribbon cable that the power supply can be moved away far enough to gain access to the five circuit cards that make up the brains of the machine. The circuit boards are very high quality double-sided boards, surrounded with a thick aluminum stiffener and edge-protecting ring. The boards plug into a hand-wired backplane which interconnects the boards to each other, and to a separate circuit board which handles the decimal point selection logic and display driving functions.

The SOBAX sans Case, with Power Supply Module Slid Out

A unique feature of the first-generation Sony SOBAX calculators was the provision for the machines to be powered by other sources of power than the AC powerline. The BP-11E battery pack provided an external rechargeable battery pack that would operate the calculator independent of AC power. The DCC-2AW auto power adapter would allow the SOBAX to be powered from the cigarrette lighter outlet of an automobile. These external accessories were plugged into a special power connector located on the back panel of the machines.

This particular example of the ICC-500W hails from the late 1968 timeframe, based on date codes on devices in the machine. This machine comes from a time before the large-scale availability of integrated circuits, and is made completely from 'hybridized' circuit modules. Hybrid circuits were a bridge technology between individual discrete components, and later integrated circuit technology. In these hybrid modules, a ceramic substrate is 'printed' with circuit traces, resistors, and attachment pads for other small components such as diodes, capacitors, inductors, and transistors. Sony considered these devices to be Integrated Circuits, but by strict definition, these hybrid modules are not truly integrated circuts.

A close-up View of some of the Hybrid Circuit Modules

Once the components were placed on the printed ceramic substrate, the entire assembly was dipped in a durable but non-conductive potting material, leaving only the wire leads from the substrate for connection to a circuit board. These hybrid modules could be standardized, with modules perhaps forming a single logic gate, a flip-flop, or driver. The same type of technology is used today for SIP (Single-In Line Package) packaged resistor networks. Back before integrated circuits, this type of technology was frequently used in more complex digital circuits (such as in computers), as it made for easier module-based troubleshooting, and reduced the physical size of complex electronics. The downside of this type of technology is that it is usually very vendor-specific, and nowadays, should one of the components inside one of these hybrid modules fail, there is little that can be done to repair or replace it.

The Circuit Board Cage (note delay line enclosure at bottom of chassis)

The ICC-500W SOBAX is a 14-digit, four function electronic calculator with memory. It uses Nixie tube display technology, with each Nixie tube housing the digits zero through nine and a decimal point at the right lower corner of each digit. The machine uses an magnetostrictive delay line, housed in the bottom of the chassis (inside its own metal enclosure) to store the working registers of the calculator. It operates in fixed decimal point mode, with a long slide switch that extends below the width of the display panel. The slide switch can be set to any desired decimal point position, and the calculator will take care of assuring that the decimal point will be located at that position. This allows a setting from zero to thirteen digits behind the decimal point. The machine has a memory register which is operated by [M IN] (somewhat of a misnomer, as the key actually adds the content of display to memory register), a [M OUT] key for recalling the content of the memory register to the display, and an [M C] key to clear the memory register (without affecting the display). The memory register is stored in the delay line along with the rest of the operating registers of the machine, meaning that the content of the memory register is lost when power is removed.

One of the Five Circuit Boards that make up the Sony ICC-500

The [R] key serves as an exchange key, allowing easy swapping of dyadic operands, particularly useful for swapping the dividend and divisor in division problems. The large [CLEAR] key serves as a clear-all function, clearing the machine (except for the memory register) and canceling any overflow condition. The smaller [C] key serves to clear the display register to allow for correction of input errors. The red [T] key is unusual, and operates in a manner like I've never seen before. This function allows for accumulation of products and quotients, and behaves as a separate accumulator register. This is a 'push-on/push-off' key. When pressed 'on', the function is activated, and the results of any multiply or divide operations are automatically added into a non-displayed accumulator, separate from the memory register. The accumulation of products/quotients continues until the [T] key is pressed again to turn the function off, at which time the content of the accumulator is recalled to the display, and the accumulator is cleared.

A closer view of the Sony SOBAX Keyboard and Display

The display panel has two annunciators at the left end of the display, which are illuminated by neon tube indicators behind small jewels. An overflow condition lights up an annunciator clearly stating "OVER FLOW", and locks out the keyboard to all but a press of the [CLEAR] key. A negative sign indicator lights to indicate when the number in the display is negative. The calculator doesn't know how to deal with division by zero. Doing so will cause the machine to go into a spin, which results in every digit in each of the Nixie tubes being lit at once -- the machine is looping forever trying to calculate the impossible. A press of the [CLEAR] key halts this behavior, returning the machine to normal.

A Detailed view of the Nixie Display (showing the "OVER FLOW" indicator)

A slide switch on the keyboard panel selects the rounding mode of the machine, with the rounding function again showing Sony's independence of thought with regard to how rounding should work. The rounding function occurs on the 3rd digit from the right end of the display...no matter where the decimal point is positioned. If this digit is 5 or greater, the next significant digit is incremented, and the remaining two right-most digits cleared. If the digit is 4 or less, the rightmost three digits of the display are cleared.

What Happens when Division by Zero is Attempted

The display is not blanked during calculation, and spin pretty dramatically during longer calculations. The machine benefits from leading zero suppression on display, and leading/trailing zero suppression on input, which, for a machine of the time, is a very advanced feature, and very uncommon on machines of this era. It appears that Sony invented the notion of leading-zero suppression on display-type calculators.

A View of the 'Back' of the Keyboard Assembly

The keyboard on the SOBAX uses the commonly used technology of magnetically activated reed switches, but adds a Sony twist. Each key is an individual module, with the keystalk and magnet, reed switch, and key return spring enclosed in a plastic housing. Two wires exit the housing providing connections for the reed switch. The housings are retained in the keyboard panel with small spring clips. This makes it quite a simple operation to replace a defective key, though again, being as Sony did it their way, it makes it more difficult for future preservationists to provide replacements should any of these parts fail. Fortunately, though, these switch modules seem to be very reliable.

The ICC-500 performs reasonably well, with published performance figures of 15 milliseconds for addition and subtraction, 250 milliseconds (1/4 second) for multiplication, and 400 milliseconds for division. Actual experience with the calculator bears out these figures, except in the case of the museum's worst-case division benchmark, dividing a full register of 9's by one (in this case, 99999999999999 divided by 1), which takes just under one second to perform. Published performance figures were typically averages, which explains the discrepancy, as typical divisions certainly do complete in less than 1/2 second.

Text and images Copyright ©1997-2021, Rick Bensene.