How to check servo encoder alignment
The readings to take, the order to take them in, and what a misaligned encoder looks like on the drive.
OpenGuides · from the repair bench
Servo motor and encoder guides
Practical guides for maintenance engineers and motor makers: encoder alignment, alarm codes, feedback selection, absolute encoder batteries, testing a servo motor without a drive, and when to repair or replace.
By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.
01Guides
All guides
Servo encoder alarms and what they usually mean
Fanuc, Yaskawa, Mitsubishi and Siemens feedback alarms, and whether to check the cable, the encoder or the drive first.
OpenEncoder, resolver or Hall sensor: the difference
How each feedback device works, where it is used, and how it fails.
OpenChoosing feedback for a new motor design
For motor makers: cost, resolution, temperature and drive compatibility compared.
OpenAbsolute encoder battery: what happens when it runs flat
Why position is lost, how to change the battery without a re-reference, and when the encoder itself is at fault.
OpenRepair or replace a servo motor?
Cost, lead time and the faults that make replacement the better call.
OpenHow to test a servo motor without a drive
Insulation, winding resistance, brake and encoder checks you can do with ordinary instruments.
Open02Downloads
Printable sheets
Each guide has a one-page sheet you can print and keep with the machine. All of them are on the resources page.
Servo encoder alarm quick sheet
Common encoder and feedback alarms on Fanuc, Yaskawa, Mitsubishi and Siemens drives, what each usually points to, and what to check on the cable and connector first.
PDF · 1 page · 4 KB · free, no sign-up
Download PDFEncoder alignment checklist
What to record before removing an encoder, the order of checks after refitting it, and the readings that tell you commutation is right before the motor goes back on the machine.
PDF · 1 page · 4 KB · free, no sign-up
Download PDFServo motor encoder quick reference
Encoder families, interfaces, counts per revolution and the motors they sit on: Fanuc pulsecoders (alpha A64, A1000), Mitsubishi OBA/OSA, Yaskawa UTOPH, Tamagawa, Heidenhain ECN/EQN/ERN and SICK SKS/SRS/SRM.
PDF · 2 pages · 8 KB · free, no sign-up
Download PDF03Services
When the guide is not enough
Servo motor repair
Multi-brand repair with load test and a printed report.
OpenEncoder repair
Encoder, resolver and Hall sensor repair, alignment and programming.
OpenServo drive repair
Drive repair for the common families.
OpenPLC migration
PLC and HMI upgrade when spares are no longer available.
Open04Enquiry
Send the nameplate or encoder label
A clear photo of the motor nameplate and, if the cover is off, the encoder label is enough to start. We reply with whether it can be repaired and a quote.
Message received
Our team replies by email or WhatsApp, usually the same working day. For a line-down motor, WhatsApp +91 97866 22233.