0874

Common Causes

• Loose, damaged, or disconnected servo link cable or connector
• Faulty inverter unit control board
• Faulty FCP board
• Noise or wiring damage causing CRC, parity, or format errors on the link

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code bit 0 = Time-out error — no response on the servo link; code bit 1 = Parity error in received data; code bit 2 = Double reception error; code bit 3 = Double transmission error; code bit 4 = Format error in the received frame; code bit 5 = CRC error — data corrupted in transit; code bit 6 = Modulation code error; code bit 7 = Address pointer error
2. 2Read the code's lower four digits (YYYY) as a bit pattern: bit 0 = time-out, bit 1 = parity error, bit 5 = CRC error, bit 8 = disconnection — this tells you whether you are chasing a broken connection or data corruption.
3. 3If bit 8 (disconnection) or bit 0 (time-out) is set, lock out power, allow the drive to discharge, then check every servo link connector and cable run between the NC/FCP side and the inverter unit for looseness, bent pins, or a severed cable.
4. 4If CRC, parity, format, or modulation code bits are set, suspect noise or a marginal cable — inspect routing away from power cables and check shielding and grounding.
5. 5If the link hardware checks out, the inverter unit control board is the next suspect.
6. 6If the error persists after the board, the FCP board is the remaining faulty location — replace or have it tested, and contact Okuma service with the alarm number, code and object if it still returns.