I picked up a "spares or repair" 0.8l ultrasonic cleaner. It looks like a customer returned unit (i.e. brand new in box, but not working).
I must admit the build quality leaves a lot to be desired, but I got it working. The main fault was the pin pushed out of its connector housing that you can see in the pictures. This was causing the display to lock up, and the ultrasonic element to run constantly.
I reseated the connector, then discovered the buttons didn't work. There were no spacers on the bolts, so I replaced those with some 5mm lengths of plastic tubing recovered from a kitchen surface spray bottle cut to length with a scalpel.
There is also a lot of hot snot used in construction, presumably to stop everything shaking loose while in use.
The PSU is missing a retaining bolt, owing to the poor layout. If fitted, it would short the heatsink to ground.
The base is also poorly constructed with the holes for the bolts drilled very close to the edge of the steel sheet. I'm glad I didn't pay too much for it.
Having said all that.. it works, and the results are impressive. I don't think my glasses have been this clean since their last visit to the optician. It also made a good job of cleaning an old Canon iP4300 print head, I have however run out of ink, so I can't test it.
It cleaned some silver jewellery and my brass front door keys.
I'll try it on a couple of small PCBs next, since that was the main reason for purchasing it.