HP 3478A Repair

I’ll start with noting that these repairs on the HP 3478A (and many other older HP instruments) are well documented amongst the community. I mostly referenced the excellent write-up here by Tom.

I mostly followed the procedure described, I backed up the SRAM via querying the contents over GPIB, wired in a pair of AA batteries to keep the SRAM active, and replaced the lithium cell. After which, followed it up with replacing the old RIFA caps, which are infamous, and as expected, had cracked in my instrument.

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UPS Expansion Butchery

I picked up a used Emerson Liebert Vertiv GXT4 Double-Conversion UPS a little while back to better handle the dirty power coming from my portable generator, while feeding my server cabinet at the house. The internal batteries work fine, but I wanted to wire in some additional batteries for extra runtime before the generator would actually be needed. Unfortunately, it seems the external battery pack cable is exceedingly hard to find.

As my UPS is a 48V battery pack model, I believe the right cable for mine would be model number GXT3CABLE48V1, unfortunately, that proved to be effectively impossible to reasonably source. I did find some GXT3CABLE144V1 model cables that in the pictures looked essentially identical, so I took a gamble and ordered one.

I’ve found that the cables are effectively the same, but the plugs are keyed differently. So, all I needed to do was shave off the keying on the cable, and it worked fine in my UPS. Below is a photo of the shaved version above, and the stock version below. Hopefully someone else finds that helpful as well.

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Laser Tape Measure

I got one of the little Bosch laser tape measure devices as a gift for the holidays. It’s an impressive little device, and is remarkably accurate. I’m curious how it makes the measurement, because the timing requirements to directly measure time of flight for a laser beam over the course of a couple feet are quite tight.

I used the same photodiode setup I put together for measuring the accuracy of a mechanical clock, and took a look at the signals.

It does seem like they’re doing some modulation on the laser beam, but I haven’t dug further to come to any conclusions yet on how they’re actually deriving a distance. Pretty neat tool though.

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Customizing a Smart Plug – Part 2

In the first part of this endeavor, I opened up a some Wyze Plug Outdoor units, and reprogrammed the ESP32 inside with my own control code. These units have been working really well, and I wanted to add some of the indoor model to the collection, as a different form factor option.

Unfortunately, these units are glued together, and are much more of a pain to open. However, once you do eventually brute force your way in, the process is very similar. Hook up some wires to a few pins on the microcontroller, and upload the new code.

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3D Printed Lego Wreath

Came across this Lego inspired wreath on Thingiverse, and decided we should print up a set for the house, and one for a friend as well.

Took a few continuous days of printing, but I’m pretty pleased with the results.

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