SRVO-063

Check for companion encoder alarms

On teach pendant, press MENU > ALARM > F1 [TYPE] > select 'SERVO'. Review all active servo alarms. Look specifically for SRVO-068, SRVO-069, or SRVO-070 on the same axis as SRVO-063.

Press F3 [DETAIL] on each alarm to see the specific axis number and timestamp. If multiple alarms occurred within 1-2 seconds, the earliest alarm is typically the root cause.

Check encoder cable connections

Power down robot. Inspect encoder cable at motor and at axis control board (on robot mounting base or through cable track). Check for bent pins, oil contamination, or loose connections. Check cable routing for pinch points or excessive bending near J1-J3 cable track.

LOTO (Lockout/Tagout) required. Disconnect main power and verify zero voltage before handling cables.

Check encoder cable continuity

Using multimeter, check continuity from encoder connector at motor to axis board connector. Serial pulse coder typically uses 5-pin connector. Check power pins (+5V, GND) and data lines for opens or shorts between conductors.

Resistance between data signal pairs should be >10kΩ. If <1kΩ between any data and ground, cable is compromised. Fanuc encoder cables part numbers start with A860 or A860-0XXX series.

Clear alarms and test

If cable fault found and corrected, power on controller. MENU > ALARM > F2 [RESET] to clear alarm. If SRVO-068/069/070 do not return but SRVO-063 persists, proceed to battery or pulse coder replacement causes.

If SRVO-068/069/070 clear successfully and SRVO-063 remains, the rotation counter data may still be corrupted from the original fault. Battery backup or pulse coder replacement may still be necessary.

Check battery voltage and alarm history

MENU > SYSTEM > F1 [TYPE] > Variables. Toggle to $DMR (Dynamic Maintenance Register). Check $DMR.$BAT_ALM (battery alarm flag). Also check MENU > ALARM > F5 [HIST] for recent SYST-035 (low battery) or SYST-103 (battery alarm) entries.

Even if no current battery alarm exists, check alarm history. If SYST-035 occurred within 30 days, battery was depleted long enough to corrupt encoder data.

Measure battery voltage at controller

Access battery pack on controller CPU board (typically inside control cabinet on right side panel). Using voltmeter, measure total battery pack voltage at connector. R-30iA/iB standard battery: 6V nominal (four 1.5V AA lithium or two 3V lithium). Voltage <5.4V indicates replacement needed.

Do not disconnect battery with controller powered on. This will immediately corrupt all battery-backed data including mastering, position registers, and programs.

Replace battery and reset rotation counter

If battery voltage low, replace battery per manufacturer procedure (Fanuc part A98L-0031-0025 or equivalent). After replacement, MENU > SYSTEM > Variables > $MCR (Macro System Variables). Set $MCR.$SPC_RESET = TRUE. This resets the serial pulse coder rotation counter registers.

Set $MCR.$SPC_RESET[axis] = TRUE where [axis] is the specific faulted axis (1-6) to reset only that axis, or set without index to reset all axes. Variable only accepts TRUE; it auto-resets to FALSE.

Power cycle and verify alarm clear

After setting $SPC_RESET, perform full power cycle (turn controller keyswitch OFF, wait 30 seconds, turn ON). Allow controller to boot completely. Check MENU > ALARM to verify SRVO-063 has cleared.

If alarm does not clear after power cycle, rotation counter hardware in pulse coder itself is faulty. Proceed to pulse coder replacement.

Re-master affected axis

MENU > SYSTEM > Master/Cal > [affected axis]. Jog axis to master position (reference notch or zero-degree mark). Set master count and perform single axis mastering per standard procedure. Verify mastering by jogging axis through full range and returning to known positions.

Mastering requires robot in T1 mode with enabling device. Ensure adequate clearance and verify mechanical reference marks are intact before mastering.

Inspect pulse coder physical condition

Power down and LOTO robot. Access motor/encoder on affected axis. Inspect pulse coder housing for cracks, oil contamination, or corrosion. Check encoder shaft coupling for damage. On J4/J5/J6 wrist axes, check for coolant or cutting fluid infiltration if applicable.

LOTO required. For wrist axes J4-J6, support wrist weight before loosening any mechanical components to prevent dropped load.