Zoom mechanism faults
The helicoid and cam track inside a zoom lens are precision-machined parts lubricated at the factory with specific greases. Over time that lubricant migrates, dries out, or becomes contaminated, which makes the zoom ring stiff or causes grinding. A drop can also misalign the zoom cam, making the barrel wobble or collapse at one end of the range. Tim dismantles the barrel assembly, cleans the helicoid threads, replaces the lubricant with the correct grade, and re-aligns the groups before reassembly.
Autofocus motor problems
Ring-type USM (Canon), Silent Wave Motor (Nikon), or linear motor drive systems can strip internal gears, snap drive couplings, or fail at the aperture coupling between the lens and body. AF motors on older lenses driven by the camera body’s screw drive are also prone to wear at the screw contact point. Tim can diagnose whether an AF fault is the lens, the body, or the coupling between them, which avoids unnecessary work on the wrong unit.
Aperture blade contamination
Oil on the aperture blades is a common fault on lenses produced in the late 1990s and 2000s. Lubricant migrates from the focus helicoid onto the blades over time, causing them to stick open, stick closed, or move sluggishly. This produces inconsistent exposures and, on very oily blades, visible bokeh artefacts. Cleaning the aperture assembly requires dismantling the rear element group, degreasing the blade stack, and reassembling without introducing new contamination.