Results of transducer testing:
No connection between the centre (positive) contact and earth when disconnected from the boards output. (as expected)
When transducers are connected to the boards output, there is about 0.3 Ohms to earth. (this doesn't sound right to me).
The outer contacts on the transducers (negative) are connected to earth, very low resistance reading 0.3 Ohms.
I will compare these readings to the new board when it arrives.
I didn't do solder connection to the transducers, as 250 deg C max is recommended.
I was going to use heat sinks and solder them, but ended up connecting them with small nuts and bolts.
