0870

Common Causes

• Failed magnetic encoder or damaged encoder wiring
• Excessive gap between the magnetic encoder head and its gear
• Mismatch between the actual PG gear tooth count and the servo data file setting
• Abnormal A-phase or B-phase signal voltage from the encoder

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code XXXX=A = A-phase voltage is abnormal; YYYY shows the A-phase voltage; code XXXX=B = B-phase voltage is abnormal; YYYY shows the B-phase voltage; code XXXX=C = Magnetic encoder data error; YYYY is fixed at 0; code XXXX=other = Servo data file gear-teeth setting (PG gear teeth x 4) at the count-over error; YYYY shows the detected encoder count
2. 2Read the code: XXXX=A means abnormal A-phase voltage, B means abnormal B-phase voltage (YYYY shows the measured voltage), C means a magnetic encoder data error, and any other value is the gear-teeth setting (PG gear teeth x 4) seen when a count-over error occurred, with YYYY showing the detected count.
3. 3Power down and lock out; allow the drive to discharge, then inspect the magnetic encoder wiring and connector for damage, coolant, or loose pins.
4. 4Check the physical gap between the magnetic encoder head and the gear; an oversized gap weakens the signal and causes phase voltage errors.
5. 5If the code indicates a count-over (XXXX other than A/B/C), compare the actual number of gear teeth on the PG gear against the servo data file value and correct the mismatch.
6. 6If wiring, gap, and data all check out, replace the magnetic encoder.
7. 7If it returns after these checks, record the alarm number, code and object and contact Okuma service.