My brother has an early to mid 90's LB-10 that keeps blowing the drive modules on the spindle drive board. They replaced all the modules, it lasted maybe a couple hours before it happened again. So he bought a used drive board and it ran for about 10 hours before it blew the modules on the used board.
When the modules are replaced the spindle runs smooth as can be and stops perfectly. Had a CNC service tech check the machine out and he couldnt find anything wrong while it was running the day before it blew them the last time.
Anyone have an idea what could be causing this? Is the spindle motor itself in need of repair? If so wouldnt it show some obvious problems while ramping up and down or stopping? Could incoming voltage spikes cause this sort of issue?