USM Drive Test

This menu lets you test the USM motor to make sure it is working properly and the software will suggest likely causes of failure if the motor does not respond correctly.

This test is especially important after replacing the USM motor or taking the lens apart.

Testing Process:

• The test runs automatically and checks how well the motor performs. If something is wrong, the software will tell you what the likely problem is (like a loose part or worn-out piece inside the lens) so you know where to look.

Notes:

• When testing a Zoom lens, run the test at both Wide and Tele positions
• Most failures are caused by improperly tightened motor cams or worn plastic collars. Checking these areas first can save time and avoid unnecessary part replacements.

USM Frequency

This menu helps you fix Auto Focus problems like focusing too fast, too slow, or acting unstable by adjusting the USM frequency

Use this menu to fine-tune the lens frequency:

• You'll need to open the lens to solder two wires to the lens board.
• Route the wires out through the AF/MF switch opening.
• Reassemble the Lens and connect your frequency counter.
• Adjust the Frequency using the slider.
• Press ‘Write’ to save your changes.

⚠️ Read our article: Frequency Counters are inexpensive

Tips:

• Autofocus fluctuations are more noticeable in hot or cold conditions.

USM Duty Cycle

This menu helps you fix Auto Focus problems like focusing too fast, too slow, or acting unstable by adjusting the USM frequency.

The menu controls the duty cycle, which is how long the motor is turned On and Off during each pause. Most lenses work on a 50/50 balance. If the balance is off, the focus can become rough or unreliable.

• Most lenses use a 50% duty cycle, where the high and low pulses are equal in duration.

You should use this menu if:

• If the is not focusing smoothly
• You replaced the USM motor or main board
• You are fine-tuning lens after repair

⚠️ Always perform USM Frequency Adjustment first (if supported by the lens), before adjusting the Duty Cycle.

Automatic Calibration:

• If the lens supports automatic duty cycle calibration, no external equipment is needed. Simply press ‘Calibrate’, and the software will complete the process in about one minute.