Pentax lens focus ring snapping

Question

I have a Pentax DA 35mm lens that was stored in the camera bag for a while.

When trying to use it today, I noticed that the focus ring motion is not smooth. It is "snapping" at specific intervals, 3 times for the full ring travel. Smooth motion when starting rotation, then offers some resistance, then smooth again, resistance again, smooth until it stops.

It seems this happens when the focus thread (in the rear) is oriented the same way. There were some tiny liquid droplets on the rear of the lens.

The lens seems to work well otherwise, but I worry the effect this will have on the camera auto-focus mechanism.

My questions are why this may have happened, and how to fix it?

Answer 1

The mechanisms are linked. There is probably some debris that entered the lens and is stuck in the gears, so the gears have worn out. In either case, you must sent it to be repaired. This did happen to another non-weatherproof Pentax lens of mine and unfortunately it takes time to send it and wait for it to be repaired but stop using it in the mean time as the debris may be damaging the gears further.