Teardown: The DOCSIS 2.0 cable modem falls out of favor

Article By : Brian Dipert

DOCSIS 2.0 cable modems may not be state of the art, but they're still sufficient for many cable Internet customers' needs. And they're also fairly interesting inside.

Back in April 2014, I picked up an open-box Motorola SB5101U cable modem for $14.49 with free shipping, as a backup to my existing cable modem. The SB5101U was a DOCSIS 2.0-based product, versus the then-latest DOCSIS 3.0 cable modems shipping from multiple suppliers (not to mention now-latest DOCSIS 3.1 successors). But the Internet broadband speed tier I was getting from Comcast wouldn't have taken advantage of beyond-DOCSIS 2.0 capabilities, anyway. And did I mention that the modem, one of the more popular options of the DOCSIS 2.0 era, was only $14.49?

2.5 years later, DOCSIS 3.0 cable modems are pretty darn inexpensive, too. And Comcast is growing increasingly un-fond of DOCSIS 2.0 devices. So instead of continuing to cling to the idea of potentially pressing the SB5101U into service someday, I decided to instead dissect it for your and my common curiosity-satisfaction pleasure … hopefully in a non-destructive manner, so that I could then donate it for someone else to potentially press into service.

I'll begin with a series of box shots:

I was particularly fond of the following messaging on the external-package markings; if you're a long-time reader, you're not surprised:

Flip back the box top and here's the first thing you'll see:

Underneath the cable modem itself, which we'll see more of shortly, Motorola also included Ethernet and USB cables, a documentation-and-software CD, various pieces of paperwork, and a power supply:

Here's a closeup of the "wall wart," revealing relevant output voltage/current and plug polarity specs, among other things:

Now for some outside shots of the modem itself. According to this discussion thread, the SB5101U is the "retail" version of the service provider-bundled SB5101, and also adds both a standby button and a USB interface option (in addition to obligatory Ethernet):

Believe it or not, the torx on the back of the unit, above the Ethernet port, is the sole screw holding the chassis together:

I thought there might be more at the underside, under the sticker, but I found only plastic tabs there:

After removing the screw (thank you once again, iFixit toolkit) and popping the tabs, I was able to pry the two halves apart from the back:

I never got the front side separated, but was still able to slip out the PCB in the middle:

Note the light guides intended to route the PCB-located LEDs’ outputs to the front panel:

Voila: the PCB topside:

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