Lens Help Needed Please (Pentax)

[DaydreamJay]

Hi, about 3 months ago I bought a Pentax smc FA 50mm 1:1.4 lens off ebay, it was 2nd hand and cost me £200. I love it and have used it a fair bit, I was going to take it with me tonight as I going to photograph a band.

I've just encountered a problem with it, it sticks/jams when turning the focus, it's always at the same point (about half way) and I have to jiggle it about to get it to move again. I'm really peed off as I use it all the time and I was wondering if it's likely to be fixable and if I can do it myself.

It hasn't been dropped or damaged in any way. What are the usual causes for problems like this and can they be resolved easily?

Thanks in advance.

 

[DaydreamJay]

Update:

I've just taken the back off the lens and a single ball bearing and a very tiny screw fell out. Any ideas? It doesn't seem to jam any more.

And how traumatic is taking a lens apart!?! Jesus, I think I'd have rather performed brain surgery on myself.