I'm searching the schematics of the pcb from an LKB220 welder unit. The name of this PCB is LKC12.
This PCB is also used in Migmag 160 and 240.
The service manual of the welder unit gives only parts of the schematics. Mine welder will not start (contactor vibrating!) I suspect a issue in the command circuit of it (K1 relay or the driving opamp ?)

With kind regards,