Zaphod B. Scientific-Laboratory electronics engineer NZ

Anyone ever had a motor drive assy issue whereby there is a motor enable and a run signal reaching the first pcb yet the lower drive module "enable" red LED is not turning on? The error message comes up in the display as "Tach signal not present" but this is only because the motor drive control module is not being "enabled" I'm guessing the fault s/w table isn't smart enough to isolate the fault any further? Don't want to have to purchase a new motor drive module as this is probably an smd logic ic fault on one of the motor drive pcb's which can easily be repaired. Any help will be greatfully reciprocated thanks Z