At work, I just had to modify an interconnect board, which various sensors plug into, and in turn connect to the main data acquisition system.
Previously, the Data Acquisition System provided power to the remote sensors.
The newer models do not, and separate power needs to be supplied at the interface board.
I have just done the necessary mods and added the external power supply.
And nothing worked.
The brand new Switch-Mode Power Supply, an RS 'essentials' cheapy, was DoA.
The work required to remove this effing thing is *highly irritating*, requiring as it does, the disconnection of 10,000 wires from screw-terminals.
Will do better testing this time before re-installing the board in it's cabinet.