Mitsubishi MDS Alarm 17 (A/D Converter Error) — Causes, Diagnosis & Fixes

Mitsubishi MDS alarm 17 means an A/D converter error — an error was detected in the current feedback (FB). The analog-to-digital converter that digitizes the motor current measurement inside the drive failed its check. Current feedback is the innermost control loop — a drive that cannot trust its current measurement cannot control torque — so it stops. Applies to both servo and spindle MDS units.

Mitsubishi's investigation sequence, in prose

1. Check the repeatability:
   • The error always repeats → replace (repair) the drive unit. The A/D stage or its reference/supply on the control board has failed — there is no external cause for a hard A/D fault. Bench reality: this is a control-board component repair (converter, reference, local rails) — considerably cheaper than a new unit.
   • Returns to normal but recurs → environmental; continue.
2. Check the ambient environment — temperature, noise, grounding. An A/D converter running at the edge of its temperature range, or hammered by conducted noise from poor grounding, produces intermittent conversion errors on a board that tests fine cold on the bench.

Diagnosis checklist (in order)

1. Constant alarm 17 → drive unit control board: bench repair or exchange.
2. Intermittent → cabinet temperature and drive cooling first, then grounding and shielding.
3. Recurring despite a healthy environment → the board's A/D stage is ageing — repair on your schedule.

Related guides

• Mitsubishi MDS alarm 32 (power module overcurrent)
• Mitsubishi MDS alarm 10 (undervoltage)
• Mitsubishi M70/M80 alarm list