Help with Pentax camera mounts

[Algoessailing]

I have a Pentax ZX-M and a ZX-7 and several lenses. I recently purchased a used Vivitar 80-200 zoom P/K lens. This lens fits the "m" but not the "7". I have another vivitar P/K lens that fits both bodies, and an albinar p/k lens that fits both bodies. Any Ideas why this one won't work? The pentax website shows that both bodies take the same mounts except the "m" also takes an S mount. Is my new lens and S mount? How can I tell if p/k lenses are the right mount? Thanks for any help
DAve

 

[ksmattfish]

I thought all Pentax bayonet mounts were the same K-mount, but I'm not up on the latest models. Maybe they changed it some.

 

[tr0gd0o0r]

I'm with him, that sounds really strange. The lens should fit on both bodies. Maybe the lens is bent or something. Do the other lenses STILL fit on both bodies, is it possible that one of them got out of shape somehow? Not trying to insult your abilities, but are you sure you were putting it on the right way?

Just trying to throw out afew things that are running across my mind.

 

[Algoessailing]

Thanks for the reply, this one lens is the only difficult one, and it is pretty old. I have to work to get it on the "m" but I am affraid to force it onto the "7" (not that it would go if i did). the mount does look different than the others, but only slightly. Most have two small piece sticking out of the mount side of the lens, one fixed the other moveable. The fixed one though is about 20mm wide (curved with the shape of the mount) where the others are only about 5mm wide. Thanks again
DAve