On 14 Aug 2008 19:30:19 -0400, (Samuel M.
Goldwasser) put finger to keyboard and composed:

Franc Zabkar writes:

If you read the text of the various inventions, it appears that they
all use a 40kHz piezoelectric transducer driven by a two-transistor
oscillator. One patent states that "the oscillation frequency is
dependent mainly upon the characteristics of the piezo element". I
think what you are trying to do is akin to changing the natural
oscillation frequency of a quartz crystal by playing around with
external components, ie it makes no sense.

Well, he could go lower by adding mass to it. Higher? Chip off a piece?

In all honesty, I was going to suggest something along those lines,
assuming it is at all feasible. Years ago I had a problem with a 25MHz
crystal that had begun to oscillate at a higher frequency (not an
overtone). I suspect that either a piece had chipped off as a result
of an accident, or maybe a dag that was present during the trimming
process finally fell off in normal usage.

Alternatively, the OP might try procuring a ready-made replacement:
http://www.annon-piezo.com/product/P...er-cleaner.htm

For example, the ANN-2560 is rated at 59kHz and 25W.

- Franc Zabkar
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