whit3rd writes:

On Nov 27, 7:53 am, bud wrote:
I have a 2 qt Sonix IV Ultrasonic Cleaner that has a very weak
cavitation. I tried the aluminum foil test and it only produced one
perforation in a 10 minute span. I also observed that it only raised
the water temp about 8 degrees with the heater off.

That doesn't spell "very weak" to me, but maybe I'm just clueless.
The innards of these cleaners have two features that can result
in lower output:
(1) mechanical coupling of ceramic ultrasound transducer to
the tank is through a high-tech glue blob, so if that glue cracks, the
transducer vibrates 'free'.
(2) Often the oscillator has a tuned circuit that acts to impedance-
couple the transducer. Tuning can change over time.

I've used some hotmelt adhesives for ultrasound, but I presume the
transducer coupling is epoxy-like, so it can't be easily fixed.
Inspect
and if it's bad, consider rebuilding options. If it's the transmatch
network, I've seen adjustment options (use a PLASTIC driver to
turn the ferrite screw); an AC current meter will indicate extra power
drain if you are increasing the power transfer to the water that way.

The transducers can also crack.

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