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Prying eyes: Busted weather station

05 Oct 2015  | Brian Dipert

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The supplemental PCB isn't detachable (at least without doing some de-soldering, that is), but peering at its underside reveals, in addition to the connector, a capacitor:



And a crystal oscillator:



Remove six more screws and the underside of the main PCB becomes accessible:



La Crosse's engineers sure like to use black epoxy, don't they? In the upper right corner of the second mystery IC is what I believe to be another crystal oscillator. To the left of it is a row of solder points that drive the LCD (stay tuned for what they mate with). Beyond them are solder points for two of the four battery terminals (the other two are built into the back panel), and the backside of another secondary PCB to which the temperature sensor is mounted. Surrounding the secondary PCB are four switches, which proximity-mate with front panel buttons. And at the far left edge of the image are eight solder-point connections to the first secondary PCB we saw earlier, which connects to the loop antennas. See the bubbling on the PCB around them, most noticeable below them? Hold that thought for a minute.

First, let's look at the backside of the LCD, now that the PCB obscuring it has been removed:



Remember the row of solder points I mentioned a bit ago? They proximity-mate to the elastomeric connector strip you see on the LCD's left edge in the above image.

I'll wrap up this writeup with a guess as to why the weather station's wireless transmitter-to-receiver link failed. Regular readers may remember a series of teardowns last year whose test subjects were rendered nonfunctional by a nearby lightning strike. Suffice it to say that this year has so far been similarly "electric," albeit not (yet at least) quite as close in proximity. Our recently installed POTS line, for example, rings connected phones once each time a lightning bolt is unleashed overhead, believe it or not.

With that amount of environmental EMI coupling going on, I'm guessing that the weather station receiver's antenna has gotten zapped, and with it the receiver circuitry attached to the antenna. Therefore the visible damage on the PCB underside, which I just pointed out. Agree or disagree, readers? Sound off in the comments.


About the author
Brian Dipert is Editor-in-Chief of the Embedded Vision Alliance. He is also a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company's online newsletter. And he's an off-hours freelancer as the Principal at Sierra Media, where he contributes to (among other things) the Brian's Brain blog at EDN Magazine. Brian has a BSEE from Purdue University in West Lafayette, IN. His professional career began at Magnavox Electronics Systems in Fort Wayne, IN, where he worked for an aggregate 2.5 years as a co-op engineer. Brian subsequently spent eight years at Intel Corporation in Folsom, CA, holding a variety of roles in the company's nonvolatile memory group. During this time, Brian also authored and co-authored four technical reference guides published by Annabooks Press. He then spent 14 years (and five months) at EDN Magazine; at the conclusion of his career there, he was the senior technical editor covering consumer electronics-targeted ICs, software and sub-systems.


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