With Amazon’s smart plug teardown “in the books”, our engineer turns his attention to some TP-Link counterparts, this first one the best behaved of the bunch per hands-on testing results.

Two months back, I introduced you to several members of TP-Link’s Kasa and Tapo smart home product lines as successors to Belkin’s then-soon and now (at least as you read these words, a few weeks after I wrote them) defunct Wemo smart plug devices. I mentioned at the time that I’d had particularly good luck, from both initial setup and ongoing connectivity standpoints, with the Kasa HS103:

An example of which, I mentioned at the time, I’d shortly be tearing down both for standalone inspection purposes and subsequent comparison to the smaller but seemingly also functionally flakier Tapo EP10:

Today, I’ll be actualizing my HS103 teardown aspiration, with the EP10 analysis to follow in short order, hopefully sometime next month. What’s inside this inexpensive device, and is it any easier to disassemble than was Amazon’s Smart Plug, which I dissected last month?

Plain is appealing

Let’s find out. As usual, I’ll begin with some outer box shots of the four-pack containing today’s patient. You may call the packaging “boring”. I call it refreshingly simple. As well as recyclable.

Sorry, I couldn’t resist including that last one .

Now for the device inside the box, beginning with a conceptual block diagram. Interestingly, although I’d mentioned back in December that TP-Link now specs the HS103 to handle a current draw of up to 15A, the four-pack (HS103P4) graphic on Amazon’s website still list 12A max:

Its three-pack (HS103P3) graphic counterpart eliminates the current spec entirely, replacing it with the shadowy outline of an AC outlet set, which I suppose is one way to fix the issue!

And now for some real-life shots, as usual (and as with subsequent images) accompanied by a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:

See that seam? I ‘spect that’ll be a key piece for solving the puzzle of the pathway to the insides:

And, last but not least, all those specs that the engineers out there reading this know and love, including the FCC certification ID (2AXJ4KP115):

Cracking (open) the case

Now to get inside. Although I earlier highlighted the topside seam, I decided to focus my spudger attention on the right side to start, specifically the already visible gap between the main chassis and the rubberized gasket ring:

Quickly results-realizing that I was indirectly just pushing the side plate (containing the multi-function switch) out of its normal place, I redirected my attention to it more directly:

Success, at least as a first step!

Now for that gasket…

At this point, however, we only have a visual tease at the insides:

Time for another Amazon-supplied conceptual diagram:

And now for the real thing. This junction overlap gave me a clue of how to start:

It wouldn’t be a proper teardown without at least a bit of collateral damage, yes?

Onward, I endure it all for you, dear readers:

Voilà:

Boring half first:

PCB constituent pieces

Now for the half we all really care about:

As with its Amazon smart plug predecessor, the analog and power portions are “vanilla”:

The off-white relay at far right on the main PCB, for example, is the HF32FV-16 from Hongfa. Perhaps the most interesting aspect of the analog-and-power subsystem, at least to me, is the sizeable fuse below the pass-through ground connection, which I hadn’t noticed in the Amazon-equivalent design (although perhaps I just overlooked it?). The digital mini-PCB abutting the relay, on the other hand, is where all the connectivity and control magic take place…

In the upper left corner is the multicolor LED whose glow (amber or/or blue, and either steady or blinking, depending on the operating mode of the moment) shines through the aforementioned translucent gasket when the switch is powered up (and not switched off):

Those two unpopulated eight-lead IC sites below it are…a titillating tease of what might be in a more advanced product variant? In the bottom left corner is the embedded 2.4 GHz Wi-Fi 1T1R antenna. And to its right is the “brains” of the operation at the other end of the antenna connection, Realtek’s RTL8710, which supports a complete TCIP/IP “stack” and integrates a 166 MHz Arm Cortex M3 processor core, 512 Kbytes of RAM and 1 Mbyte of flash memory.

Stubborn solder

Speaking of power pass-throughs…what about the other side of the main PCB? The obvious first step is to remove the screw whose head you might have already noticed in the earlier shot:

But that wasn’t enough to get the PCB to budge out of the chassis, at least meaningfully:

Recall that in the Amazon smart plug design, not only the back panel’s ground pin but also its neutral blade pass through intact to the front panel slots, albeit with the latter also split off at the source to power the PCB via a separate wire. The line blade is the only one that only goes directly to the PCB, where it’s presumably switched prior to routing to the front panel load slot.

In this design, that same switching scheme may very well be the case. But this time the back panel neutral connection also routes solely to the PCB. Note the two beefy solder points on the main PCB, one directly above the screw location and the other to the right of its solder sibling. I was unable to get either (far from both of) them either successfully unsoldered from above or snipped from below. And all I could discern on the underside of the PCB from peering through the gap were a few scattered additional passive components, anyway.

So, sorry, folks, I threw in the towel and gave up. I’m assuming that those two particular solder points, befitting the necessary stability not only electrically but also mechanically, i.e., physically, leveraged higher-temperature solid or silver solder that my iron just wasn’t up for. Or maybe I just wasn’t sufficiently patient to wait long enough for the solder to melt (hey, it’s happened before). Regardless, and as usual, I welcome your thoughts on what I was able to show you, or anything else related to this product and my teardown of it, for that matter, in the comments!

—Brian Dipert is the Principal at Sierra Media and a former technical editor at EDN Magazine, where he still regularly contributes as a freelancer.

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