🚀 go-pugleaf

I have several ultrasonic humidifiers that have bit the dust.  They
all ran for quite a while (several months to a year or two) and then
exhibited reduced vapor output.  Taking a peek inside verifies that
the little squirt of water above the transducer is still there, but a
lot smaller than when the unit was new.  The circuitry is usually
quite simple - a power supply and a one transistor oscillator.

I haven't had a chance to put a scope on one of these things yet, so I
thought I might find out if any of you network geniuses have fiddled
with them and can give me a hint for what to look for.  My questions:

1.  Is there a common failure mode that these units experience?

2.  Do the transducers go "bad" after a while?

3.  Are the transducers resonant devices that don't work well if they 
    are driven at a frequency that does not match their natural
    frequency?  Do I need to adjust the oscillator frequency?

4.  Where does one get replacement transducers?  It recall that 
    a surplus outfit called Herbach & Rademan (sp?) used to sell 
    transducers, but they may have been for hydrophones, not
    humidifiers.  Does anyone know of any others?

My wife, who has just had some sinus surgery, is anxiously awaiting
your replies.

- Jim
--
-----------------------------------------------------------------------
J.V. Pieronek                           Internet: jvp@ll.mit.edu
M.I.T. Lincoln Laboratory               (617) 981-3468
Lexington, Massachusetts  USA