Focus Motor Crackling / Grinding — UltiBox or Lens Drive Fault¶

Summary¶

If a focus motor makes a crackling / grinding sound while moving, treat it as a physical drive-chain or UltiBox output problem before assuming a Flair software fault. The confirmed field case was resolved by replacing the UltiBox after the lens and motor had both been checked.

Symptoms¶

Focus gear makes a crackling, grinding, or sustaining-position sound.
Lens is not obviously stiff by hand.
Swapping to a different motor does not clear the symptom.
The motor is not being driven past a cine lens hard stop.

Community Solutions¶

[CONFIRMED] Swap or inspect the UltiBox if lens and motor checks pass¶

2021-07-09 — Kyle / Tom D / Dan Gottesman

Check that the lens ring moves freely by hand.
Try a different focus motor on the same lens channel.
Confirm the motor is not reversed into the lens hard stop.
Power down and restart the UltiBox.
If the symptom remains with a free lens and known-good motor, inspect contacts / cabling and swap the UltiBox.

The field report concluded: "we just replaced the ulti box and it seems work fine."

confidence_score: 0.86

[LIKELY] Check physical gear mesh and motor direction¶

2021-07-09 — Dan Gottesman

If the sound is mechanical rather than electrical, check:

Motor gear is not too tightly meshed with the lens gear.
Gear teeth are not damaged.
Motor direction is not driving the lens into the wrong hard stop.
Lens is a cine lens with reliable mechanical stops, not stills glass with ambiguous end travel.

confidence_score: 0.72

Image description: focus motor / lens drive photo from a case where the motor made a crackling or grinding sound; resolved by replacing the UltiBox after lens and motor checks. Searchable terms: focus crackling; focus motor grinding; lens motor crackle; UltiBox focus fault; motor sustaining position.

Media Text / Description¶

Image description: focus motor / lens drive photo from a case where the motor made a crackling or grinding sound; resolved by replacing the UltiBox after lens and motor checks.

Media 1: Image description: focus motor / lens drive photo from a case where the motor made a crackling or grinding sound; resolved by replacing the UltiBox after lens and motor checks. Searchable terms: focus crackling; focus motor grinding; lens motor crackle; UltiBox focus fault; motor sustaining position.

WhatsApp Excerpts¶

[9/7/2021, 8:35:20 pm] ~ kyle.k: hello everyone. have you guys seen this message before? could you know how to solve this problem?

[9/7/2021, 8:36:02 pm] ~ kyle.k: our focus gear make crackling sound while it moves

[9/7/2021, 8:43:37 pm] ~ Simon Wakley: Have you tried a different motor. Does the lens move easily by hand?

[9/7/2021, 8:48:25 pm] ~ kyle.k: yes it is not stiff lens and also we tried with different motor

[9/7/2021, 8:49:41 pm] Tom D: Have you tried powering down and up again the ulti box on the arm?

[9/7/2021, 8:52:25 pm] ~ Dan Gottesman: a crackling sound? I wonder if it’s either a physical issue (something in the gears) or an electrical issue (bad contacts?).

any chance you can make a recording?

[9/7/2021, 8:56:19 pm] ~ kyle.k: i will try this after make motion