Homebrew PCBs

In article <20050310192228.GB2891@...>,
   Peter Johansson <peter@...> wrote:
> Here's a thought on agitation:  Find a gear motor that runs somewhere
> arround 30 RPM.  Mount a disc perhaps 2-3 inches in diameter with an
> offset center to the motor.  Mount underneath one edge of the tray.
> Might something like this do the trick?

How about sitting the tray on the cone edges of an old loudspeaker - say
about an 8". With a tone generator and an amplifier you could experiment
with different frequencies to see which produced the desired effect -
ultrasonic?