Mitsubishi MDS alarm 19 means an encoder communication error in synchronous control — an error was detected in the MACHINE-side encoder of the SECONDARY axis during speed-command synchronization. This is a servo-side alarm on synchronous-axis configurations (twin-drive gantries and tables where two motors run one axis): the secondary axis's scale/encoder feedback chain — often running through an MDS-B-HR interface unit — dropped out.
Mitsubishi's six steps, in prose
- Check the secondary axis's encoder parameter — SV025 (pen, position encoder): the machine-side encoder type must be declared correctly for the secondary axis specifically — a restore or setup that got the primary right and the secondary wrong produces exactly this alarm.
- Check the linear scale → MDS-B-HR connection — including Mitsubishi's wonderfully specific check: is the screw connecting to the MDS-B-HR wound down? A backed-off terminal screw at the interface unit is a documented, real-world cause — tighten it. Inspect the whole scale-to-HR connection while there.
- Jiggle-test the encoder connectors (drive end and encoder end) — loose → install correctly.
- Power OFF and meter the encoder cable — faulty → replace.
- Swap-test to split drive vs encoder side — the alarm follows the guilty unit.
- Ambient environment — machine grounding and cable shielding: gantry axes have long cable runs through moving carriers, making them the most noise- and flex-exposed feedback chains on the machine.
Tip: On a synchronous pair, always ask which axis the alarm names — the SECONDARY's machine-side chain is the suspect, even though the symptom (gantry down) feels global. And take alarm 19 seriously on gantries: a secondary axis running on corrupted feedback in synchronization is how gantries rack and bind. The drag-chain section of the secondary's scale cable is the single most common physical find — flex it while metering.
Diagnosis checklist (in order)
- Verify SV025.pen on the SECONDARY axis.
- Inspect the scale→MDS-B-HR connection; tighten the terminal screws.
- Reseat/jiggle connectors; meter the cable with flexing (drag-chain section especially).
- Swap-test drive vs encoder side; repair/replace accordingly.
- Intermittents → grounding and shielding of the long secondary-axis runs.
Related guides
- Mitsubishi MDS alarm 18 (main encoder initial communication)
- Mitsubishi MDS alarm 32 (overcurrent)
- Mitsubishi M70/M80 alarm list
Alarm 19 on your gantry or twin-drive axis? JJ Automation diagnoses synchronous-axis feedback chains — scales, MDS-B-HR units, cables — on site in NCR, and repairs MDS drives at component level. WhatsApp us or call +91 88022 12394.