4174

Common Causes

• Servo link cable or connector loose, broken, or disconnected
• Noise, poor shield bonding, or bad grounding causing CRC, parity, or format errors
• Inverter unit control board communication hardware failure
• FCP board fault corrupting or dropping servo-link traffic

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code bit15 = Second B-buffer error; code bit14 = Second A-buffer error; code bit13 = First B-buffer error; code bit12 = First A-buffer error; code bit11 = MT buffer error; code bit10 = Relay processing error; code bit9 = Receive interface overran incoming data; code bit8 = Link disconnection detected
2. 2Record the object and the YYYY bits before reset; bit8 points to a disconnection and bit0 to a timeout, while bits1, 4, 5, and 6 point toward corrupted data rather than a fully open link.
3. 3Lock out and discharge the drive system before handling servo-link connectors or boards.
4. 4Inspect and reseat the servo link cable at the FCP side and inverter side; replace the cable first if there is chafing, bent pins, oil contamination, or a loose latch.
5. 5Check shield clamps, cabinet ground straps, and cable routing so the servo link is not bundled with motor or brake power leads.
6. 6If bits12-15 or bit10 are set, suspect buffer or relay handling in the control path; isolate by swapping the inverter control board and FCP board only after cabling is proven good.
7. 7If the alarm returns after these checks, record the alarm number, object, and full bit pattern and contact Okuma service.