SRVO-018

Identify the Faulted Axis

On the teach pendant, press MENU > ALARM > F1 [TYPE] > select 'Alarm Log'. Note the axis number specified in the SRVO-018 alarm detail line (e.g., 'Group: 1 Axis: 3'). Record the timestamp to correlate with any robot motion that may have triggered the fault.

Check if the alarm occurred during power-up (brake always engaged) or during motion (dynamic brake operation). Power-up faults suggest a hard short, while motion-related faults may indicate intermittent issues.

Power Down and Lock Out Robot

Execute emergency stop, turn controller keyswitch to OFF, and open main disconnect breaker. Apply lockout/tagout per facility safety procedures. Wait 5 minutes for capacitor discharge before opening any panels or connectors.

DC bus capacitors retain lethal voltage up to 5 minutes after shutdown. Never work on motor or amplifier connections with power applied or before waiting the full discharge period.

Access and Disconnect Motor Brake Connector

Remove robot covers to access the affected axis motor. Locate the brake power connector (typically a 2-pin white connector near motor base). Disconnect the brake connector and inspect pins for discoloration, corrosion, or carbon tracking that indicates arcing. Take a photo for documentation.

On J1/J2/J3 axes, brake connectors are typically at the axis housing. On J4/J5/J6, follow the intra-arm cable bundle to the motor location. Mark connector orientation before removal to ensure correct reassembly.

Measure Brake Coil Resistance

Using a calibrated digital multimeter set to ohms (Ω), measure resistance across the two brake coil pins on the MOTOR side of the disconnected connector (not the cable side). Compare reading to specifications: J1/J2/J3 typically 60-80Ω, J4/J5/J6 typically 40-60Ω. Any reading below 10Ω or above 200Ω indicates coil failure. Also measure insulation resistance from each brake pin to motor ground (should be >10MΩ).

Ensure multimeter leads are in good condition. Poor lead contact can give false high-resistance readings and lead to incorrect diagnosis.

Replace Motor Brake Assembly if Failed

If brake coil resistance is out of specification, the motor brake assembly must be replaced. Order the correct brake kit using the motor serial number label (format: αisXX-XXXX). Follow the maintenance manual procedure for brake replacement, which typically requires axis removal and disassembly. After replacement, verify brake holding torque per manual specifications and clear alarm history before return to service.

After brake replacement, run the brake diagnostic from MENU > SYSTEM > F1 [TYPE] > Master/Cal to verify proper current draw. Normal brake current should be 0.8-1.2A during release. Document baseline values for future reference.

Inspect Base and Mid-Arm Cable Connections

With power locked out, inspect the large circular connectors at robot base (typically labeled CF1, CF2, CF3) and any mid-arm connectors (J3 arm). Look for oil contamination, pin corrosion, bent pins, or moisture inside connector shells. Check that strain reliefs are secure and cables are not kinked or showing outer jacket damage.

Oil leaks from gearboxes or hydraulic balancers commonly contaminate these connectors. Clean thoroughly with electrical contact cleaner and dry completely before reconnection.

Perform Cable Continuity and Isolation Tests

With brake connector at motor disconnected and base connectors still attached to amplifier, measure resistance from brake pins at the amplifier-side connector to ground. Consult the connection manual for your robot model to identify correct brake pins (typically labeled BRK+ and BRK- or similar). Any reading below 100kΩ to ground indicates insulation breakdown in the cable. Also check for shorts between brake lines and adjacent power or encoder pins.

Use a megohmmeter (500V setting) for more sensitive insulation testing if available. Cable insulation resistance should exceed 10MΩ when new, but anything above 1MΩ is generally acceptable for continued service.

Perform Flex Test on Suspected Cable Segments

If static resistance tests pass, the fault may be intermittent. With multimeter connected to brake circuit, manually manipulate the cable through its full range of motion, particularly at the base entry, J3 joint, and any areas showing wear. Watch for resistance changes indicating intermittent shorts. Pay special attention to areas where cables pass through or near metal edges.

Common failure points: base entry boot (cable flexes with J1 rotation), J3 upper arm area (high flex duty cycle), and areas where cable ties are over-tightened causing insulation compression.

Inspect Internal Cable Routing and Dress

If external inspection passes, remove robot covers to inspect internal cable routing. Verify cables follow the dress diagrams in the mechanical unit maintenance manual. Look for cables rubbing against sharp edges, trapped between moving parts, or routed too tightly through joints. Check for signs of previous repair or modification that may have compromised cable protection.

Take photos of cable routing before and after any adjustments. Many SRVO-018 faults traced to cables are actually caused by improper reassembly after previous maintenance work.

Replace Interconnection Cable if Faulty

If cable testing confirms insulation failure or shorts, the entire interconnection cable assembly must be replaced. Order by robot serial number as cable lengths and pinouts are model-specific. After installation, verify proper cable dress, secure all strain reliefs, and perform continuity testing before power-up. Clear alarm history and run brake diagnostic to verify current draw is within 0.8-1.2A specification.

Never attempt to repair or splice robot interconnection cables. These are critical safety circuits and must be replaced with OEM cables to maintain robot certification.