Help with jammed focus on Pentax F 70-210

I was going to buy this used lens at a local store for $89 but it would not focus. The focusing is completely jammed and just twitches and goes "clunk" when the camera tries to focus. Otherwise the lens looks perfect.

I am going to buy the lens for $10 with lens caps. Hey the caps are worth that.

Has anyone ever seen this problem? Any suggestions or assistance in hopefully reviving this highly rated lens?

Powell

Personally, I wouldn't try it again on a camera until you've freed it by hand.
Try gently turning the AF coupler (with a small watchmaker's type screwdriver) back and forth to see if that frees it. You could try turning the focussing ring but it would be quite easy then to strain an internal mechanism.
Might be best to get a reputable dealer to take a look at it!

The clerk tried the lens on a couple of the stores bodies.

I tried a screw driver gently in the focus drive. It is locked solid at infinity. There is some slack but no give at all. Guess I will try opening the lens and see what I can find.

The good news is when I went to purchase the lens the manager gave it to me free! - with lens caps.

Powell

G'day.
I had a F 35-105 do the same thing.
I ripped it apart and found a small piece of grey plastic had broken off of somewhere unknown and was jammed solid in the gears of the AF drive.
Removed the jammed plastic, reassembled, And the lens is still working fine. Buggered if I know where the plastic that was jamming the AF came from.

Hooroo.
Regards, Trevor
OZ

P.S. getting the focus back to gether so that infinity was right was a real PITA.

Thanks Trevor

Any hints on best way to get to the gears? Any other tips from your experience appreciated.

Powell