John, Thank you for the concise information. I feel comfortable enough to take the route of proceeding with a KB board.
One last question: The KB board is mains powered, does it also get grounded to earth (via the star point or alongside its two mains power lines)?
If your KBLC-19M is like the KBLC-240D I have repaired there is no earth terminal
the only earth connection you could make is to the aluminium heatsink the PCB is fastened to
Have you used an earthed metal enclosure for all your control electronics ?
if so making sure the heatsink is making a connection to the enclosure is good enough