The LED bulb has a polarity, although not indicated on the bulb itself. It also fits in the beacon socket in two ways. So it the light does not function, turn the LED bulb 180 degrees in its socket.
The EDM machining process inherently emits a large amount of EMC noise. This radiated energy can be picked up by cables and cause interference to other signals traveling over those cables.
The KFlop control board connects to a control PC via USB. USB however is a consumer grade interface, which was not designed to cope with large amounts of EMC. For this reason the interface to the BX17 arc generator is RS-485, which has a higher robustness against EMC than USB.
If the USB cable between the PC and Kflop is unprotected and long, the EMC radiation of the arc will cause noise in the communication and will cause the communication to fail with the following error:
It is therefore essential to keep the PC<–>KFlop USB cable as short as physically possible. In order to do so, the best apprach is to mount the PC directly under or next to the KFlop and have both of them in the same shielded and grounded metal enclosure.
All cables that travel from and to this enclose should be properly shielded and connectors should use full metal EMC shielding connector hoods. The only cable that is unpractical to shield is the mains power cable. In order to prevent EMC to travel down this cable into the enclosure, it is highly recommended to use a EMC power line filter.
The details in a schematic overview are given here: