Eleven years ago, my wife and I experienced the aftereffects of our first close-proximity lightning blast here in the Rocky Mountain foothills, clobbering (among other things) both five-port and eight-port Gigabit Ethernet (GbE) switches, both of which ended up going under the teardown knife. The failure mechanism for the first switch ended up being non-obvious, in sharp contrast to the second, whose controller chip ended up with multiple holes blown in its package top:
One year (and a decade ago) later, lightning struck again. No Gigabit Ethernet switches expired this second time, although we still lost some other devices.
Fast forward to 2024, and…yep. This time four GbE switches ended up zapped, two of them eight-port and two more five-port (fate was apparently playing catch-up after previously taking a pass on switches). The former two will be showcased today, with the others following soon. Then there’s the three-bay NAS; you will have already have seen that teardown by the time this piece is published. And another CableCard receiver (we’re three for three on those), along with another MoCA transceiver…you’ll get teardowns of those in the near future, too.
Today’s dissection patients are from the same supplier—TRENDnet. They hail from the same product family generation. And, as you’ll soon see, although their outsides are (somewhat) dissimilar, their insides are essentially identical (given the naming and release date similarities, that’s not exactly a surprise). Behold the metal-case TEG-S82g (hardware v2.0r, to be precise):
which, per Amazon’s listing, dates from September 2004, and the plastic-case TEG-S81g (again, hardware v2.0r), also initially available that same month and year:
Let’s start with the metal-case TEG-S82g. Following up on the stock photos shown earlier, here are some views of my specific device, as usual accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes (the TEG-S82g has dimensions of 150 x 97 x 28 mm/5.9 x 3.8 x 1.1 in. and weighs 364 g/12.8 oz.). Front:
Left side:
This next one, of the device’s backside, begs for a bit more explanation. Port 8, the one originally connected to one of the two spans of shielded Ethernet cable running around the outside of the house, is unsurprisingly the one that failed (therefore the electric tape I applied to identify it).
The other ports actually still work, at least for the first minute or few after I power on the switch, but eventually all the front panel LEDs begin blinking and further functionality ceases:
Onward. Right side:
Top:
and bottom:
Here’s its “wall wart”:
Those screw heads you might have noticed on both device sides? They’re our pathway inside:
Here’s our first view of the PCB inside:
Four screws hold it in place. Let’s get rid of those next:
Let’s see what we’ve got here. At the bottom are the eight Ethernet ports, next to (at the bottom right) the DC input power connector. Thick PCB traces running from there to the circuitry cluster in the upper right quadrant suggest that the latter handles power generation for the remainder of the board. And above each two-port combo is a Bi-TEK FM-3178LLF dual port magnetic transformer. Here’s the specific one (at far right) associated with failed port 8:
At the top edge are (at far right) the power LED, next to eight activity LEDs, one for each of the ports. And below them is the system’s “brains”, a Realtek RTL8370N 8-port 10/100/1000 switch controller. It may very well be the same as the IC in the 8-port switch teardown from 11 years ago, although I can’t say for sure, as that one had chunks of its packaging (therefore topside markings) blown away! That said, this design does use the same transformers as last time.
Here’s a close-up of the RTL8370N and the aforementioned circuitry to its right:
Now let’s flip the PCB over and have a look at its backside:
No obvious evidence of damage here, either. Here’s another port 8 area closeup (as I was writing this, I paused to revisit the hardware and confirm that those white globs are just dust):
Now for its plastic-case TEG-S81g sibling, with listed dimensions again 150 x 97 x 28 mm/5.9 x 3.8 x 1.1 in. (albeit this time tapered in the front), although the weight is (unsurprisingly, given the shift in case material construction) decreased this time around: 186 g/6.6 oz.:
This time, port 5 failed. The other seven ports remain fully functional to this very day, although for how much longer I can’t say; therefore, I’ve decided to retire it from active service, as well, in the interest of future-hassle avoidance:
The “wall wart” looks different this time, but the specs are the same:
No screws on the case sides this time, as you may have already noticed, but remove the four rubber “feet” on the underside:
and underneath the front two are visible screw heads.
You know what comes next:
And we’re in (with the tape still stuck to the top):
Let’s put that tape back in place so I can keep track of which port (5) is the failing one:
The earlier-shown two screws did double-duty, not only holding the two halves of the chassis together but also helping keep the PCB inside in place. Two more, toward the back, also need to be dealt with before the PCB can be freed from its plastic-case captivity:
That’s better:
Another set of closeups, first of the affected-port region:
and the bulk of the topside circuitry:
And now, flipping the PCB over, another set as before:
I hope you’ll agree with me on the following two points:
- The two PCBs look identical, and
- There’s no visually obvious reason why either one failed.
So then, what happened? Let’s begin with the plastic-case TEG-S81g. Truth be told, the tape on top of port 5 originally existed so that I could remember which port was bad down the road, after I pressed it back into service, and in the same “use it until it completely dies” spirit that prompted my recent UPS repair. That said, long-term sanity aspirations eventually overrode my usual thriftiness. My guess is that, given the remainder of the ports (and therefore the common controller chip that manages them) remain operational, port 5’s associated transformer got zapped.
And the metal-case TEG-S82g? Here, I suspect, the lightning-strike spike effects made it through the port 8 transformer, all the way to the Realtek RTL8370N controller nexus, albeit interestingly only with derogatory effects seemingly after the chip had been operational for a bit and had “warmed up” (note, as previously mentioned in the earlier eight-port GbE switch teardown, the lack of a heatsink in this design). As the block diagram in this RTL8370N datasheet makes clear, the chip is highly integrated, including all the ports’ MAC and PHY circuits (among other things).
~1,300 words in, that’s “all” I’ve got for you today. Please share your thoughts in the comments!
—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.
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