In article .com,
"nortonfan" wrote:

I'm attempting to bring my Bulova model TR250 ultrasonic watchmaster
cleaner back into service. I have found two rectifier diodes blown,
along with the circuit protection fuse. The wafer transducer is epoxied
to the the tank, and I am not sure how to go about testing for
problems. It appears to be solidly mounted to the tank with no visible
fractures to the epoxy joint. However, I suspect there is a problem
with it, as it has lost its cleaning abilities. This model seems t
have been made in the mid '80s.

NF-

Are you familiar with crystal oscillators? That is roughly how the
ultrasonic transducer is connected, but as a high power oscillator. The
remainder of any electronics would be for a timer/controller.

The transducer probably has a ceramic element, and is constructed somewhat
like a capacitor. It should have electrodes fired and/or plated onto
opposing surfaces, one of which may be glued to the bottom of the tank.
One failure mode would be a fractured ceramic. You might check it as a
capacitor to see if it is shorted or leaky.

I don't know how practical this would be, but one test might be to connect
the transducer to a sensitive oscilloscope and see if mechanical
vibrations result in electrical waveforms.

Be sure you always have a liquid in the tank when testing. Unloaded, the
transducer is more likely to fracture.

When you get it working, you should wear hearing protection while it operates.

Fred