I have a 1991 Okuma lb15 with a 5020l control. For the last several weeks I have been getting a 110 A SDU Alarm. Sometimes the machine would run for 4 hours, sometimes for 30 minutes, or sometimes only for a couple minutes. It has finally reached the point where the machine won't come up at all and just alarms out:drowning:. According to the LEDs on the drive it is experiencing a motor overload or a heat sink over temp. I tried using a jumper across the wires that connect to the temp sensor on the heat sink and the same thing on the spindle motor overload, but neither of those helped. I have spoken with techs at Hartwig Okuma and they seem to think it may be a bad top board on the spindle drive. I am open to suggestions or if anyone knows what component(s) on these drives commonly fail please let me know. Any help will be appreciated.