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Focus Motor D/A Overflow — No Motor Movement Despite Encoder Reading

CONFIRMED ALL RIGS

Summary

Focus position number moves on screen but the motor does not turn. Flair reports a D/A Overflow error on the focus axis. This error means the digital motor command from Flair does not match the analogue encoder feedback within the minimum tolerance — the motor and encoder are not in agreement. Causes include: wrong encoder polarity relative to motor direction, a failed UltiBox port or the entire UltiBox hardware, or a damaged motor/cable. The motor may work on a different UltiBox port (e.g. reassigning focus to the zoom port as a workaround).

Symptoms

  • Focus axis shows D/A Overflow error or trip
  • Focus position number changes on screen but the physical motor gear does not move
  • Motor gear can be turned freely by hand (it is engaged but not driving)
  • Swapping to a spare motor does not help
  • The axis works in Independent mode on some Flair versions but not in FFO / FFT
  • Issue began without any known cable or motor change

What D/A Overflow Means

Timothy Heys Cerchio (MRMC): "D/A Overflow generally means that there is no consistency between motor signal and encoder feedback. Digital to Analogue — the Digital motor request from Flair does not correspond to an equivalent (within minimum tolerance) Analogue feedback from the Encoder on the motor."

In other words: Flair is commanding the motor to move, the motor may be receiving a signal, but the encoder is not reporting back the expected movement. Possible causes: 1. Encoder polarity mismatch — motor and encoder are wired in opposing directions 2. Failed UltiBox port — the amplifier/encoder reader on that specific port has failed 3. Failed UltiBox board — all ports unresponsive (see related issue) 4. Damaged motor cable — intermittent connection 5. Humidity damage — see IO-focus-motor-humidity-desiccant.md

Fixes

Fix 1 — [CONFIRMED] Try a different UltiBox port

Reassign the Focus axis to a different port (e.g. Zoom port, Port 6) in Setups → Axis Setup, and physically move the motor cable to that port:

  • If focus now works, the original port has a failed encoder reader or amplifier — UltiBox needs MRMC service
  • The remaining ports are still usable while the faulty port is bypassed

Fix 2 — [LIKELY] Check encoder polarity

If no spare UltiBox is available and only the focus axis is affected on a standard MRMC motor:

  • In Axis Setup, try reversing the motor direction (tick/untick the Reverse checkbox)
  • If the encoder polarity is opposite to the motor polarity, the overflow occurs immediately on engagement
  • For custom or third-party motors: check that encoder and motor power wires are matched correctly (swapping red/black motor power wires reverses the motor; the encoder must agree)

Fix 3 — Replace UltiBox

If all ports on the UltiBox are unresponsive (focus, zoom, and auxiliary all fail), the UltiBox board itself has failed. See IO-ultibox-all-ports-dead-hardware-failure.md for the diagnostic procedure.

WhatsApp Excerpts

[23/1/2022, 7:58:44 pm] Timothy Heys Cerchio: It was a hardware issue! No response from any of the ports on the main UltiBox. D/A Overflow generally means that there is no consistency between motor signal and encoder feedback.

[23/1/2022, 8:10:48 pm] ~ .: Focus number move. But in motor not move.

[23/1/2022, 8:16:19 pm] ~ .: Independent work. But with 6.43.15 flair.

[23/1/2022, 7:24:13 pm] Timothy Heys Cerchio: @Eko — have you tried reassigning the port in Axis Setup to Port 6 and connecting the Focus cable to the Zoom output?

Official Documentation

Flair Classic Manual — Ch.5 Setups: Axis Setup — p.33