Problem with my Planer 50/1.7

[dakoo]

My contax mount ziess planer T* 50mm f/1.7 is having a problem.

One of its screws has been unscrewed, some internal screw that i can't see.
Now the front filter ring, now displaced from one side.

My guess is there are two screws, one of them has been lost (i can hear the screw moving loose inside the lenses when i move the lense up & down, but I can't see it).
The lense is not suffering in performance though, it focuses normally.

I want to fix the lens it is a good idea to do it by myself.
And any guide as how to do it ?

These are the pics of error & normal photo for comparison

[Kathmandu]

I am shooting in the dark but I think - the operative word "think", that if you unscrew the front out( but not completely out )further and then tip it down- you may find a metal/ring/washer of sorts that will slide down the front tube-( gap between the front tube and the focusing tube) you may have to shake it to make it slide down. If its that ring it must be gently straightened ,aligned back over the the tube, then the tube screwed back, slowly. That ring must go all the way down over that tube and rest on the bottom of the tube on a ridge that the tube has, it may have slipped over that ridge preventing you to focus all the way out- hence the difference in the gap. I hope I understood you well enough.

If its a screw loose inside-I would try and shake the screw out through the back i.e. if its a screw it should be obvious and drop down. Then its time to unscrew the back , remembering/documenting where each component and screw comes from.Take the back off and see where the screw came from; so you know where it comes from.

Did you buy this used? Theres a lot of modified or modification attempted Planars out there. I hope this is helpful. If not I am sure you will find help.

Its to your benefit to take it to an expert repairer,before you muck it up,-it can get quite challenging if you have not done it before. Unless you want to make it a learning project.

I would also wait here to see if anyone here responds -there's a lot of knowledgeable people here.

[dakoo]

This issue is now resolved..
Got some help here http://forum.mflenses.com/infinity-tune-for-contax-lens-t7011.html

@Kathmandu : Thanks for the help, it turned to be much easier.
The screw was in the front ring with the name/lable. So didn't have to go all the way back.

Thanks guys.

[monopix]

Too late now, but for anyone else looking for similar info, I have some info on stripping one of these at www.monopix.co.uk/zeiss50mm.shtml