Production can return after the encoder cable is pulled through the embedded conduit, re-terminated near the drive, and verified conductor by conductor. The installation described has a motor-to-drive distance under 60 ft, but that dimension is not a cable-length approval; confirm the permitted length for the selected SureServo components before cutting anything.
Reject the quick fixes first
Do not force an assembled encoder connector through a conduit that cannot pass it. Connector damage, bent contacts, or a damaged backshell can create an intermittent feedback fault that appears only after the axis starts moving.
Do not cut the cable and join conductors color-to-color without recording the pin mapping. Similar colors, paired conductors, drain wires, and shields can be confused once the jacket is removed. A wrong connection can interrupt feedback or place voltage on the wrong circuit.
A terminal strip is workable when it sits close to the drive and the shielded construction remains intact up to the termination area. Long untwisted or unshielded pigtails are the recurring bad fix. They increase the loop area exposed to switching noise from the servo power cable and other conductors.
Check the route before cutting
Measure the conduit and inspect the entire pull path. The deciding reading is the smallest usable internal diameter, including bends and existing conductors, compared with the largest encoder connector dimension. Also check whether either end of the conduit can accept the connector after removing only an external hood or strain-relief component that the manufacturer identifies as serviceable.
| Check | Reading or observation | Decision |
|---|---|---|
| Connector clearance | Connector and pulling protection fit through every bend | Pull the intact factory cable; do not splice it. |
| Connector clearance | Connector cannot pass without force | Continue with a documented cut-and-splice plan. |
| Cable length | Actual routed length, including service loops | Compare it with the approved length for the selected drive, motor, and cable. |
| Termination information | Every connector pin and shield connection can be identified | Proceed to baseline testing. |
| Termination information | Any conductor, shield, or connector contact is unidentified | Stop and obtain the applicable manufacturer documentation. |
The installation request identifies an MS 17 pin cable end and a 3M 10120 cable end. Treat those identifiers as selection clues, not as a pinout. Use the exact cable drawing for the purchased assembly; the supplied reference is the official SVC-EHH-n cable drawing.
Record the electrical baseline
Disconnect the encoder cable from both the drive and motor. Never perform continuity or insulation tests through connected electronics. Use a low-energy continuity meter for conductor mapping; apply an insulation tester only when the cable and connected devices are explicitly rated for that test voltage.
- Photograph both connectors, their orientation, and all labels.
- Assign a temporary identifier to every connector contact shown on the applicable drawing.
- Measure continuity from each contact at one end to its corresponding contact at the other end.
- Record which conductors belong to shields, drain paths, or connector shells.
- Check for continuity between conductors that the drawing shows as separate. An unexpected connection must be corrected before the cable is cut.
This record is the acceptance baseline. If the original cable already has an open conductor, intermittent continuity, or an unexplained cross-connection, replacing or repairing that defect comes before conduit work.
Decide whether the splice is viable
Place the terminal blocks next to the drive, inside a suitable enclosure, so the unavoidable unshielded section stays as short as the hardware permits. This location also keeps the splice accessible for measurements without burying it in the conduit.
| Condition | Meaning | Next action |
|---|---|---|
| All conductors and shield paths are mapped | The splice can reproduce the factory connections | Select terminals that accept the actual conductor size and type. |
| Paired or shielded construction is visible | Cable geometry contributes to noise immunity | Preserve each pair and shield relationship through the shortest possible transition. |
| Shield must be opened for a long distance | The feedback circuit gains a larger noise pickup area | Change the enclosure or terminal location. |
| No reliable pin map is available | A continuity-only reconstruction may miss shield or pair requirements | Stop and request the exact drawing or a supported cable solution. |
Keep encoder wiring separated from servo output power wherever the route permits. When the existing conduit forces proximity, cable shielding, intact pair geometry, and minimal exposed length become more significant. Do not add an undocumented shield connection at the terminal strip; duplicate the factory cable drawing and connector-shell arrangement.
Cut, pull, and splice the cable
- Lock out power and verify that the drive DC bus has reached the safe condition specified by its documentation.
- Mark the planned cut near the drive end, leaving enough cable for strain relief, dressing, and one controlled re-termination. Do not place the terminal strip where routine panel work will pull on it.
- Apply durable labels to both sides of every conductor before separating anything. Carry the contact identifiers from the baseline sheet onto the labels.
- Cut the drive-end connector from the cable. Protect the cut end from dirt, moisture, and pulling damage.
- Pull the cable through the conduit using the cable jacket or an appropriate pulling grip. Do not transfer pulling force through the small encoder conductors.
- Mount the terminal blocks close to the drive. Provide strain relief for both cable sections so terminal screws or clamps do not carry cable tension.
- Strip only the jacket length needed for termination. Maintain twists and shields up to the terminals.
- Reconnect every conductor by recorded contact identity, not by color alone. Reproduce each documented shield, drain, and connector-shell path.
- Inspect for loose strands, exposed copper, mixed pairs, and shield material touching signal terminals. Close the enclosure before energizing the drive.
Verify before returning the axis to service
With both ends still disconnected, repeat the same measurements used for the baseline. Check every contact end-to-end, verify that separately mapped conductors remain isolated, and confirm each documented shield path. Flex the new termination gently while watching the meter; a changing reading identifies a weak clamp, broken strand, or poor strain relief.
Reconnect the motor and drive only after the cable matches the original contact map. Power the system and read the drive diagnostics before commanding motion. An encoder or feedback indication at standstill sends the work back to the pin map, terminal tightness, shield transition, and connector seating.
Run the axis first under controlled conditions at low commanded motion. Confirm correct feedback direction, stable position or speed indication, and repeatable operation through several starts and stops. Then test through the required operating range while watching for faults that coincide with acceleration, deceleration, nearby switching loads, or cable movement. Those patterns point toward noise coupling or an intermittent termination rather than a tuning correction.
After production is restored, document the splice location, terminal-to-pin map, cable drawing used, and final measurements. Mark the modified assembly so a future replacement is not mistaken for an unaltered factory cable.
FAQ
How do I splice a SureServo encoder cable?
Map every connector contact first, cut near the drive end, and reconnect the conductors on terminal blocks mounted beside the drive. Keep pair disruption and unshielded length as short as the termination hardware permits.
How do I pull a SureServo encoder cable through small conduit?
Measure connector clearance through the smallest bend first. If the connector cannot pass, label and cut the drive end, protect the cable, and pull by the jacket or a suitable grip rather than by the encoder conductors.
How do I test the encoder cable after splicing it?
Disconnect both ends, verify every contact end-to-end, check for unintended cross-connections, and confirm the documented shield paths. After reconnection, check drive diagnostics and test controlled motion before restoring the full operating range.
When should I stop troubleshooting a SureServo encoder splice?
Stop if the exact pin map is unavailable, a shield path cannot be identified, the cable fails isolation checks, or feedback faults remain after the splice matches the baseline. Do not keep swapping conductors or changing tuning to mask a wiring fault. Contact official AutomationDirect support with the drive, motor, cable identifiers, drawing used, route length, continuity record, and displayed diagnostic information.