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Medium Turntable 48V PSU Trips on Hard Deceleration

CONFIRMED BOTH TURNTABLE

Summary

The black "brick type" 48V power supply unit (PSU) supplied as standard with MRMC medium turntables has over-voltage protection. Hard decelerations — with or without a load on the turntable — cause a voltage spike that trips the PSU's over-voltage protection circuit. The PSU then shuts down and requires 5–10 minutes to reset before it will work again. The fix is to reduce deceleration rates or upgrade to the larger MRMC desktop-style 48V PSU.

Symptoms

  • Turntable suddenly stops responding after a fast stop
  • Power supply appears dead — no output
  • System recovers after 5–10 minutes with no other intervention
  • Problem is repeatable on fast or hard decelerations
  • Reducing speed or deceleration rate prevents or reduces frequency of trips

Systems Affected

BOTH
  • MRMC medium turntable — when using the standard black "brick type" 48V PSU
  • Not applicable if using the larger desktop-style 48V PSU (which is the upgrade solution)

Cause

The black brick 48V PSU has an over-voltage protection (OVP) circuit. When the turntable motor decelerates rapidly, it acts as a generator and feeds energy back toward the PSU (regenerative braking). This causes a voltage spike on the 48V rail. When the spike exceeds the OVP threshold, the PSU trips and cuts its output. This is normal protective behaviour for this PSU type — it is not a fault with the PSU itself.

The PSU will reset automatically, but requires approximately 5–10 minutes before output is restored.

"Please note that this PSU has an over-voltage protection and hard deceleration with or without load will cause a spike that may result in the PSU tripping. It will then need approx 5-10 minutes to reset after which point it should work as normal." — Gordon (MRMC), 2022-05-31

Solutions

Solution A — Reduce deceleration rate

Reduce the deceleration rate for the turntable axis in Flair. Gentler decelerations produce smaller voltage spikes that stay within the PSU's tolerance.

  • Add fairings (pre-roll/post-roll) to the turntable move so deceleration is spread over more frames.
  • Reduce the maximum speed of the turntable axis.
  • Avoid sharp programmed stops.

Solution B — Upgrade to the desktop-style 48V PSU

MRMC offers a larger desktop-style 48V PSU that does not have the same over-voltage tripping issue. Contact MRMC for availability and cost.

"You may also want to consider upgrading to our larger desktop style 48V PSU. Enquire for availability and cost." — Gordon (MRMC)

On-Set Recovery

If the PSU has tripped:

  1. Do not attempt to power-cycle the PSU — it will reset on its own.
  2. Wait approximately 5–10 minutes.
  3. Check the turntable axis reconnects in Flair.
  4. Before resuming, reduce the deceleration rate to prevent a repeat trip.

Source: talk.mrmoco.com — Medium Turntable - 48V PSU - over-voltage protection — Post by Gordon (MRMC), 2022-05-31

Revision History

Date Change Editor
2026-05-29 Initial extraction from forum topic 969 Tom D / Claude Code