I use a small, cheaper unheated ultrasonic, and it is not
satisfactory at all; it loosens the left over polish etc, but
doesn't really remove it,
Anna, try pouring the cleaning solution into a microwave safe
container and heating it to a nice steaming hot. Or on a hot plate,
etc. Pour back into the ultrasonic. If the ultrasonic part is working
OK, this should now do the trick. If you leave the machine running
most of the time, the ultrasonic energy itself will keep the solution
hot even without a heater.
Also, whether it removes polishing compounds or not depends a lot on
the type of cleaning solution you use, and how concentrated it is.
Some cleaning agents are great with dirty jewelry, but not so good
with the grease or wax based binders in buffing compounds. Be sure to
use a cleaning agent that’s intended for, or at least prooven with,
the type of cleaning you’re doing. In the case of buffing compounds
though, the heat is indeed important. it’s needed to help
melt/liquify the binding agents (wax, grease, etc) in the compounds.
Without that, they often won’t dissolve well A bit of ammonia added
to the solution, if it’s not incompatible with ammonia, will also
often help a lot.