Panasonic’s MINAS A5 and MINAS A6 families are two of the most widely deployed AC servo systems in packaging machines, semiconductor equipment and pick-and-place lines, and both report faults the same way: a two-part Err main.sub code on the front-panel 7-segment LED. The numbering carried over almost unchanged from A5 to A6, so one routine covers both generations, and every alarm below follows Panasonic’s official documentation.
If a driver is beyond repair, replacement stock matters. Please check our servo drive collection, which includes Panasonic units such as the MCDHT3520 alongside Yaskawa, Mitsubishi and Siemens drives.
The LED alternates main and sub code (for example “16” / “0” for Err16.0). The sub-code matters: Err16.0 (overload) and Err16.1 (torque saturation) have different root causes despite one main number. Alarm history and live torque, speed and deviation waveforms are available from the front keys or through the PANATERM utility. Clearing rules differ by class: Err16, Err18 and Err24 can be released with the A-CLR alarm-clear input once the cause is removed — Err16 cannot be cleared for at least 10 seconds after the trip — while Err11, Err14 and the encoder hardware alarms are non-clearable and require removing the cause and a power cycle. If a code returns immediately after reset, stop resetting and start measuring.
Fault manifestation: trips at power-on or randomly in operation. Trip points: approximately 70 VDC on a 100 V driver’s control supply, approximately 145 VDC on a 200 V driver.
Root causes: low line voltage or an instantaneous power failure; insufficient supply capacity, so inrush current at power-on pulls the control voltage down; an internal control-power circuit failure.
Repair steps: measure the control supply at L1C–L2C (100/200 V) or 24 V–0 V (400 V) and compare with the thresholds. Lengthen the interval between power-off and power-on. If the feed sags under load, raise the supply capacity; if the measurement is healthy and the alarm persists, the control board needs repair or replacement.
Fault manifestation: trips during deceleration of a high-inertia load, or at power-on. Thresholds: approximately 200 VDC (100 V class), 400 VDC (200 V class) or 800 VDC (400 V class) across the P–N bus.
Root causes: mains above the permissible input, or a surge from a phase-advancing capacitor or online UPS; a disconnected regenerative discharge resistor; an undersized external regen resistor; internal circuit failure.
Repair steps: measure L1–L2–L3 and remove any phase-advancing capacitor. With power off, measure the resistor between B1–B2 — an open reading means a broken resistor or wiring; replace it with the specified resistance and wattage. If the resistor is sound, lengthen deceleration times or fit a larger regen resistor. The XA/XB terminals of drivers like the MCDKT3520E — main input, B1/B2 regen terminals and motor U/V/W — are where these checks are made.
Fault manifestation: sub-code 0 means the P–N bus fell below the threshold during Servo-ON (approximately 110 VDC on a 200 V driver); sub-code 1 means the AC input dropped out longer than the time set in Pr5.09.
Root causes: brownout or momentary power loss; upstream contactor trips; a three-phase driver running on a single-phase feed (phase lack).
Repair steps: measure L1, L2 and L3 under load. When Pr5.08 (LV trip selection) is 1, a dropout longer than Pr5.09 trips the alarm — lengthen it only if brief interruptions are acceptable. On single-phase 100/200 V drivers, connect the supply to L1 and L3. Fix phase loss and undersized feeders before suspecting the board.
Fault manifestation: an immediate trip when Servo-ON is issued; sub-code 1 indicates the intelligent power module (IPM) reported the fault.
Root causes: shorted or earth-faulted motor wiring; a burned motor; welded dynamic-brake relay contacts from using Servo-ON/OFF as a start-stop switch; command pulses arriving before Servo-ON; driver hardware failure.
Repair steps: disconnect the motor leads and issue Servo-ON — if the alarm still fires instantly, the driver is faulty and must be repaired or replaced. If it holds, check insulation resistance from each motor line to earth and the phase-to-phase resistance balance; replace an unbalanced motor. Wire the machine so pulses arrive 100 ms or more after Servo-ON, and do not repeatedly re-power a failed module — the failure propagates into the drive board.
Fault manifestation: the torque command exceeds the level set in Pr5.12 and the drive trips on its time characteristic, with a 10-second minimum before clearing. Sub-code 1 means torque saturation persisted for the monitoring window (Pr6.57 on A6; Pr7.16 on A5 II).
Root causes: sustained load above rated torque; oscillation from poor gain tuning or a wrong inertia ratio in Pr0.04; machine collision or distortion; miswiring; an electromagnetic brake that never releases.
Repair steps: watch the torque waveform in PANATERM — a trace hugging the limit is a true overload, violent oscillation points at tuning. Verify brake terminal voltage and confirm the brake releases. Fix axis mix-ups, then enlarge capacity, lengthen ramps, reduce load, or re-tune gains. Drivers like the MADHT1507NA1 are common swap-in candidates when the trip traces to driver hardware.
Fault manifestation: trips on fast deceleration of large inertia; sub-code 1 indicates a failed regenerative transistor inside the driver.
Root causes: regenerative energy exceeding the resistor’s capacity; deceleration too short; wrong Pr0.16 (regeneration resistor setup).
Repair steps: check the regen resistor load factor on the panel or in PANATERM, lengthen deceleration times, and set Pr0.16 to match the wired resistor. When Pr0.16 is 2 (external resistor), the manual requires a thermal fuse or equivalent — an unmonitored resistor can overheat and burn. An Err18.1 sub-code means replace the driver.
Fault manifestation: Err21.0 is a disconnect — the driver polls the encoder every 83 µs and trips after eight consecutive unanswered requests (A6); Err21.1 is noise-induced; Err23.0 means data content is corrupted even though the link is up.
Root causes: damaged or poorly seated encoder cable; connector contamination; encoder supply below spec on long runs; motor and encoder cables bundled together so switching noise couples in.
Repair steps: re-seat both connectors, replace a damaged cable, and keep the encoder supply between 4.75 and 5.25 VDC measured at the motor end. Route encoder cables away from motor power cables with the shield landed on frame ground. If a known-good cable does not clear Err23.0, service the encoder head. Replacement cables and scales are listed in our encoder collection.
Fault manifestation: Err24.0 trips when position deviation exceeds Pr0.14; Err26.0 when speed exceeds Pr5.13 (or 1.2× the maximum motor speed when Pr5.13 is 0); Err29.0 when the deviation counter overflows beyond 230−1 feedback pulses.
Root causes and repair: thresholds set too tight; a stalled or blocked axis; poor tuning; wrong command frequency or electronic gear ratio. Confirm the motor follows the command — check torque saturation and mechanical binding first, because widening Pr0.14 on a jammed axis only masks the problem. Re-tune gains and correct the gear ratio.
Fault manifestation: Err40.0 (absolute system down) usually appears after long downtime; Err41.0 is a multi-turn counter overflow; Err42.0 is an absolute overspeed event. None clear until the absolute encoder is re-cleared.
Root causes: depleted backup battery — on the encoder line, below roughly 3.1 V the driver warns, below 2.5 V it alarms; multi-turn count beyond ±32,767 revolutions; the motor forced past its limit while powered only from the battery.
Repair steps: replace the battery box or battery-equipped cable with power applied to the encoder, then run the absolute-clear procedure. For Err41.0, either set Pr0.15 to 2 (ignore multi-turn overflow) after a proper safety assessment, or keep travel within 32,767 revolutions of home.
Fault manifestation and repair: the driver cannot identify the connected motor, usually on first power-up after a swap — the motor and driver are not a matched pair. Verify capacity codes; for example a 400 W motor such as the MHMF042L1U2 must pair with a matching driver. Replace the mismatched unit.
Most Err11/12/13 events are maintenance failures, not component failures. Quarterly: blow dust from the heat sink and fan openings, verify fan rotation, re-torque the XA/XB power terminals. Annually: measure the regen resistor between B1–B2 and log it against the nameplate; check the encoder battery on absolute axes and replace it proactively at the 3.1 V warning rather than waiting for Err40.0. Keep PANATERM parameter backups of every axis.
Can I clear Err16.0 by cycling power? Yes, but only at least 10 seconds after the trip. If it re-trips, find the mechanical or tuning cause instead of resetting repeatedly.
What is the difference between Err24.0 and Err29.0? Err24.0 is a threshold trip set by Pr0.14; Err29.0 is a hard counter overflow at 230−1 pulses, usually meaning the axis is blocked while the drive keeps counting.
