My main problem with Milltronics has been that the Tefzel surface of the ST-H transducers delaminate from the filler. Energy gets eaten up in reflections on both Tx & Rx. The units I deal with have a parameter 83 which displays dB/uV. A delaminated surface will usually cause a level >60dB, to drop to the teens or 20s. You can press against the hard surface and feel a little give when this happens. I couldn't tell you the number of these that we have replaced at around $500/unit. Finally, I started scoring the surface along the outer edge and peeling off the Tefzel. The filler within has a little give to it but exhibits good dielectric resistance the piezo within is still protected.
You really need the programmer to deal with these units. The signal thresholds for short and long pulses can be changed as the transducer reaches end of life.
The only other problem I have had is a failure of a very small Belling-Lee (English) fuse on the main board. I could only find one US supplier in Florida and they had prohibitive minimum order quantities.
Joe
