AL07B alarm in delta ASDA-A2 servo drive indicates Encoder memory busy. This means the memory of encoder is busy. Make sure the UVW connector is grounded to the heat sink of the servo drive.

1. Check if the motor is well grounded.
2. Check if the encoder cable is separated from the power supply or any high-current cable to avoid interference. 
3. Check if the encoder uses shielded cable.