SRVO-007

Physically inspect all external E-stop stations

Walk the entire cell perimeter and check every red mushroom E-stop button. Look for buttons in the pressed/latched position. Check operator pendants, material handling stations, and any integration points with upstream/downstream equipment. External E-stops often have twist-to-release mechanisms that must be manually reset.

Do not reset any E-stop until you have verified the reason it was activated and confirmed the area is safe.

Check all safety interlock devices

Verify safety gates are fully closed and latched. Inspect light curtain alignment by checking indicator LEDs (should show green/clear). Check area scanner status displays. Verify safety mat edges are not lifted or triggered. Many safety devices have local diagnostic displays showing fault conditions.

Light curtains often have alignment indicators - use the transmitter/receiver LED pattern to quickly identify beam blockage or misalignment without entering the cell.

Verify safety device reset sequence

After clearing the triggering condition, most safety devices require a specific reset procedure. Safety relays typically need power cycling or a dedicated reset button. Check if the safety PLC requires acknowledgment at an HMI. Verify all safety relay status LEDs show ready/green state before attempting robot reset.

Many Pilz, Sick, or Banner safety controllers require a 'presence test' - the E-stop must be pressed again briefly then released to confirm operator presence before the circuit will close.

Check teach pendant safety I/O status

Navigate to MENU → I/O → Digital In on the teach pendant. Observe the EES1/EES2 safety input signals (typically *SFSPDO[1] and *SFSPDO[2] system inputs). When the external E-stop is active, these will show OFF. All external devices must be reset before these signals show ON. Also check UIxxx or SIxxx inputs if external devices are mapped.

The asterisk (*) prefix on *SFSPDO signals indicates these are system-level safety signals that bypass normal I/O processing for faster safety response.

Reset the alarm on teach pendant

Once all external devices show ready and safety I/O confirms EES signals are ON, press and hold SHIFT + RESET on the teach pendant. The SRVO-007 alarm should clear. If the alarm immediately returns, the external circuit is still open or has intermittent continuity issues.

If the alarm clears but the robot servo is still not ready, check for additional latched alarms or check the CSTOPI (cycle stop input) and HOLD signals which may still be active.

Verify EES circuit wiring at controller cabinet

Open the controller door and locate the safety connection terminals, typically on the DMCR (Dual Motor Check) board or on a dedicated safety terminal strip. Check EES1 connections (often TB1 pins for EES1A/EES1B) and EES2 connections. Verify all screw terminals are tight, wires are properly seated, and there is no evidence of arcing or heat damage. Measure continuity with all E-stops in reset position.

Lock out and tag out all power sources before working inside the controller cabinet. Safety circuits may have multiple power sources including 24VDC from external safety PLCs.

Inspect external E-stop chain wiring throughout the cell

Follow the EES daisy-chain wiring from the controller through each E-stop station back to the controller return. Look for cable damage in cable tracks, pinched wires at panel entries, and worn cables at moving joints. Check all inline connectors for corrosion, proper seating, and secure locking mechanisms. Pay special attention to areas with frequent flexing or exposure to welding spatter, coolant, or heat.

Use a megohm meter to test cable insulation resistance if you suspect intermittent shorts to ground. Reading should be >10MΩ between EES conductors and ground with the circuit isolated.

Check E-stop contact condition with multimeter

Disconnect power and individually test each E-stop button's NC contact continuity. With the button reset, measure <1Ω across the NC contacts. Press the button and verify open circuit (OL). Contacts that show high resistance (>1Ω) when closed indicate worn or contaminated contacts that need replacement. Test both channels of dual-channel E-stops independently.

E-stop contacts rated for millions of cycles can still fail. Silver-based contacts can develop silver sulfide film causing high resistance. Gold-plated safety relay contacts resist this but are more expensive.

Verify safety relay output status

If external safety relays (Pilz PNOZ, Schmersal, Sick, etc.) are used, check the relay module status LEDs. Verify the safety relay outputs (often labeled K1/K2 or 13-14/23-24) show continuity when energized. Measure voltage at the controller EES input terminals - should see 24VDC loop power when circuit is complete. Check safety relay diagnostic codes if available.

Many modern safety controllers have USB or Ethernet diagnostic ports. Connect with the manufacturer's software (e.g., Pilz PNOZmulti Configurator) to view detailed fault logs and identify which input caused the safety chain to open.