My partner brought down some art supplies (aka my art porn) and cooking equipment (aka his cooking porn) our dangerous hoarding addictions into this country: stuff you can't purchase or get here.
Most of the time, there is no problem bringing in stuff into your checking baggage, though TSA often check it and leave a little "was here and checked it" ticket.
This time, he did have some art equipment (ultrasonic jewelry cleaner) in his "carry on" that got the border people got a little jumpy. I guess on Xray, these machines look like a potential problem. He was in fear of the rubber glove treatment. My partner explained what the ultrasonic cleaner was and that it is used to clean fine mechanical pens and fountain pens. He had taken it out of the box for easier and more compact travel, so without the instructions or clear identification it was unclear what it was, as the machine only says magnasonic, not magnasonic jewelry cleaner. The border guards begrudgingly let it through.
So if you are bringing an Ultrasonic cleaner or another machine down, put it in your check in baggage but realize that it could stir TSA up and they will look in your luggage, maybe with you there. Don't be scared, you haven't done anything wrong, the border just wants to check and make sure it is safe for everyone on board the plane. They are doing their job.
Several years ago, I brought down some Dr. Ph Martin paints and inks in glass eye dropper 1 oz bottles. These were put in my check in baggage and I thought nothing of it.
Then in Quito airport, the border people, asked me to open the baggage to seize the perfume I was illegally bringing in, or they were going to tax me to bring it in, whatever. I couldn't figure out what the heck they were referring to.... until I opened the bag and there were my paints. Ahhhhhh, got it.
I then showed the customs guard that it was paint not perfume and that I am an artist, whereby I showed him my art journal. His mental lights went on and he smiled and passed me right through. I thanked him for checking, shook his hand, said have a great evening and left.
Now please understand, I did not do all the thanking and shaking hand thing to be a suck, or an butt kisser, I did it in accordance with good manners of Ecuador.
Being cooperative and using good manners makes all this kind of transition thing easier, more pleasant and to be honest polite and respectful of peoples jobs. Good manners, will get you far in life and are not compromising in any way, they often diffuse a difficult situation into something as a momentary blip in your day.
Some "good" art supplies, or cooking equipment that can't be bought or acquired here can be ordered and shipped by post or can be donkey'ed down often worry free. I do most of my art supplies purchasing from Ebay or Amazon, in some cases they will ship it directly to Ecuador at a reasonable cost but be aware there may be more postal or tax extras when picking them up at the post office.