Short answer: most servo motor faults are not a dead motor. Turn the hand wheel, measure the socket voltage, reseat every plug, then restart. If the motor turns freely by hand and the fault returns at once, the control board, encoder or pedal is the part to replace.
| Symptom | Likely cause | Fix |
|---|---|---|
| Dead, no display | Fuse, power plug, board | Check socket and fuse; then control board |
| Hums, does not turn | Jam, dry machine, loose motor or encoder plug | Turn the hand wheel; reseat plugs |
| Runs by itself | False pedal signal or board fault | Unplug the pedal; replace the pedal wire or board |
| Overheats or cuts out | Low oil, heavy fabric, low voltage, weak board part | Oil, reduce load, check voltage |
| Needle stops wrongly | Position sensor or magnet | Replace the wheel sensor |
| Rough, noisy motor | Bearings, shaft, coupling | Replace the motor or fit a JACK F4/F5 servo motor set |
| Fault | JACK F4/F5/F6 | JACK A4/K4/A5 | Juki DDL-9000C | Siruba DL720 |
|---|---|---|---|---|
| Motor stuck or overload | E1, E2 | Err-08, 18, 23 | E007, E072, E079 | E07 |
| Over-voltage | Eb | Err-04, 05 | Check supply | E01 |
| Under-voltage | EC | Err-03 | Check supply | E02 |
| Encoder or Hall sensor | E4, E5 | Err-11, 13 | E071 | E07 |
Switch off and wait about five minutes before opening a control box, because capacitors hold a charge. Check plugs yourself; leave boards to a technician.
Universal direct drive servo motor · 550 W servo motor · ESDA servo motor PCB board · Universal control board PCB
Full guide with the complete symptom table: servo motor problems and error codes. Code lists: JACK F4/F5/F6, JACK A4/K4/A5, Juki and Siruba. More guides: motor buying guide and Stitch Partner guides.
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