SRVO-038

Check for concurrent battery alarms

Press MENU > ALARM > F1 [TYPE] > select 'Alarm Log'. Review for SRVO-062 (Battery zero alarm), SYST-035 (Low battery warning), or SYST-039 (Battery alarm). If any battery alarms are present, this confirms position data was lost during low voltage condition.

Battery alarms may have occurred days or weeks before SRVO-038 appears. Check the alarm log timestamps to correlate battery issues with when the robot may have been moved.

Replace battery if voltage is low

If battery alarms are present, replace the battery pack before attempting mastering. For R-30iA/R-30iB controllers, use Fanuc part A98L-0031-0025 or A98L-0031-0026. After replacement, clear alarms but DO NOT MOVE the robot yet. Battery voltage can be checked via MENU > SYSTEM > Variables > $SCR.$BATTERY_VOLTAGE.

After battery replacement, you have approximately 30 minutes of position retention. Do not move the robot until mastering is complete or position data will be permanently lost.

Attempt Single Master Recovery

Navigate to MENU > SYSTEM > Master/Cal > F1 [Master]. Check which axis shows the SRVO-038 alarm. If only ONE axis is alarmed and the robot was only slightly moved, attempt 'Single Axis Mastering' for that axis only. This preserves other axes' mastering data.

Before full mastering, try zeroing just the affected axis. Move the axis manually to its zero position (reference scribe mark), then perform single axis master. This is faster than full robot mastering.

Perform full mastering procedure

If multiple axes show SRVO-038 or single axis recovery fails, full mastering is required. Manually jog each axis to its zero position using the reference scribe marks. Go to MENU > SYSTEM > Master/Cal > F1 [Master] > select 'Mastering'. Enter password if prompted. Select all axes and press 'Yes' to execute. Verify 'Master Update Complete' message appears.

Ensure all axis brake release plugs are accessible before starting. Never leave an axis unattended with brake released on vertical axes (J2, J3) as gravity may cause movement.

Verify mastering accuracy and backup data

After mastering, move robot to a known taught position or use a reference tool to verify accuracy within specification (typically ±0.1mm for absolute positioning). Then backup mastering data via MENU > FILE > F2 [Backup] > select 'Mastering Data' and save to USB or MD: device. File will be saved as *.MAS.

Label the backup file with date and robot serial number. Store this file both on the teach pendant and on a network location. Having this backup can save hours if mastering is lost again.

Identify recently replaced components

Check maintenance records or alarm log for recent SRVO alarms that may indicate hardware replacement (SRVO-050 for overload, SRVO-001 for servo power failure). Verify which axis was serviced. Check MENU > SYSTEM > Variables > $SCR_GRP[1].$TOTAL_POWER_ON_TIME to see if time was recently reset on a specific axis indicating servo amp replacement.

After any motor, encoder, or amplifier replacement on Fanuc robots, mastering is ALWAYS required. There are no exceptions. Document this in your PM procedures.

Verify encoder cable connections

Power down the robot and inspect encoder cable connections at both the motor and servo amplifier. For separate encoders (non-integrated), verify the encoder cable (CX1 series) is fully seated with locking tabs engaged. Check for bent pins on connectors CN1 (motor power) and CN2 (encoder) at the servo amplifier.

Always follow LOTO procedures before inspecting any connections in the robot cabinet. Servo amplifier capacitors can hold lethal voltage for up to 5 minutes after power-down.

Check encoder parameter settings

Navigate to MENU > SYSTEM > Variables and verify $ENC_TYP[axis] matches the installed encoder type. For R-30iA/R-30iB, common values are 0=Incremental, 1=Absolute (serial), 2=Absolute (parallel). Also verify $ENC_PULSE[axis] matches encoder resolution (typically 8192 or 16384 pulses/rev). Incorrect parameters will cause position mismatches.

If an encoder was replaced with a different model than original, you must update both $ENC_TYP and $ENC_PULSE before mastering will work correctly. Check the encoder label on the motor for pulse count specification.

Execute mastering for replaced axis

Manually move the replaced axis to its zero degree position using the scribe marks on the axis casting. Access MENU > SYSTEM > Master/Cal > F1 [Master] > select only the axis with replaced hardware. Execute single axis mastering. If the alarm persists after mastering, the encoder may be defective or improperly installed.

After encoder replacement, it's good practice to perform a 'Zero Position Master' first, then do a full motion test, then perform 'Quick Master' to fine-tune. This two-stage approach often yields better accuracy.