Modem Teardown

Part One

The piece of electronic equipment I drew for my teardown was a modem. Initially I had chosen the mouse, however it was taken by another during the Yankee Swap. I also had some interest in other items such as the cameras, however I didn’t have the heart to take it from others who seemed very enthused about it. Therefore, while picking my replacement I stuck with the still-available pieces of equipment laid about on the table. At the instructor’s suggestion, I picked the modem because it was insisted that the modem was simple. I would say that “simple” is a serious understatement.

Going into the project, I really had no idea what the interior of a modem looked like. I had pictured a pretty complex machine so I expected to use a bit of finesse and elbow grease to take the whole thing apart. As I soon discovered, it really wasn’t the case. After unwinding all the screws I was able to see, the exterior shell came apart extremely easily. The shell came in two halves, encasing a circuit board in the middle. I looked around for more components to rip out but there were none. I stood by the workbench with a screwdriver in my hand and an empty expression on my face, I was not sure what to do. The entire process took around five minutes, required only a screwdriver, and produced a grand total of eight components (four screws, one switch, two halves of a shell, and a single circuit board). It is difficult to determine what the screws are made out of, but they are likely to be stainless steel or some aluminum alloy. The material of the enclosure was also very difficult to determine. Lengthy visual comparisons narrowed it down to likely common plastics of this application such as Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate (PC) or a blend of PC+ABS. The enclosure was probably injection molded rather than thermoformed. The circuit board itself is most likely fashioned from silicon with conductive copper alloy elements buried within it.

Figure 1. Disassembled components laid out
Figure 2. The circuit board.

After the initial teardown and cursory analysis of the materials of each large component, I decided to continue to get very granular in analyzing the circuit board and its smaller components. In total I counted approximately 281 individual items on the circuitboard. It was virtually impossible for me to identify any of the extremely small components like the transistors, therefore I chose to focus on the bigger components.

For me, most immediately noticeable thing about the circuit board was all the text. It offered a lot of clues as to what each component actually was and their origins. The machine itself was a Courier External 56k* V.92 Global Dial-Up Business Modem from USRobitics with the year 2006 stamped on the circuit board. Many of its major chips seemed to have come from all over the world. Prominently featured in this circuit board is chips from the Japanese company NEC, as well as ISSI, Innovasic, the Taiwanese company MXIC, also Texas Instruments. The entire circuit board itself was assembled in China.

Figure 3, the chips from all over the world.

Part Two

The identifiable parts are as follows:

x1 INNOVASIC IA186EB-PQF801-R-0C 16-bit Microcontroller
The INNOVASIC IA186EB-PQF801-R-0C is a 16-bit microcontroller that is embedded into this circuit board. A microcontroller is a central part of a circuit as it controls other portions and functions of the system.

x1 MXIC MX29F800CTTI-70G IC NOR Flash Memory IC 8MB
This component is a memory unit of the NOR Flash architecture. I am not really able to parse through all the technical jargon, but in essence this chip has a memory function in the circuit board.

These components are SRAM (Static Random Access Memory) chips, which are also memory units with the primary function of storing data.

x2 Texas Instruments SN75188 Quadruple Line Driver
x1 Texas Instruments SN75189A Quadruple Line Driver
x1 Texas Instruments D172B1PJ92 Quad Flat Package

As for the rest of these components, I am unable to even begin to really understand what they are used for, nevertheless I have included some data sheets I found on them.

Interestingly enough, I couldn’t find any information on any of the NEC components.

Part Three

One unexpected development or take away I had from this teardown was my new fascination for cooling and temperature management in household electronics. I spent a long while looking at the vents in the enclosure and wondered why it was the way it was. The bottom surface had no vents, whereas the sides, and the top featured vents very prominently. Having large vents on the top side makes a lot of sense. Since heat rises, the top vent provides the heated air with an upward pathway to escape, thereby passively drawing cooler surrounding air into the enclosure from the side vents, effectively creating a very slow air flow. I reckon that it’s enough of an air flow for the temperature to be more or less controlled within the operational range. Beyond having utility, the vents are also very visually dominating. These grates in particular create an interesting cage-like form. It has made me ponder about how different electronics handle the visual presentation of exterior necessities such as vents on enclosures.

Figure 4. The bottom shell, showing the side vents.
Figure 5. The top shell, showing the large grated vents.

Another thing about this modem that really stuck out to me was the international workmanship of the device. It really demonstrates the international collaboration when it comes to more (at the time) sophisticated technologies. For me, I hear about the globalized supply chain all the time, however it was very interesting for me to see it presented in such a way directly from a teardown. The engineers most likely had no choice but to source internationally due to constraints with time, cost, and etc.

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