How to adjust infinity focus on a Pentacon 200/4?

[YureW]

I've a pentacon auto 200/4, the six blades version. Taking some shots, two days ago, I noticed that it was impossible to focus to infinity: no problems with the adapter (all other M42 lenses focus properly).
Is there an easy way to fix it?

[kansalliskala]

Does it screw properly to the mount so that the upside is really up? If not - inspect the threads.

[Attila]

Perhaps it was opened and not perfectly built again, if no problem with mount.

[YureW]

Thank you, boys.

Unfortunately, the lens is broken. Making a test, today, I felt a scratch while focusing. After, the lens focussed past infinity. I took it apart, and found a missing screw, two bended slides, a little disaster.
I'll try to repair it.
Fortunately, I have another 200, a Jupiter 21, and prefer this one.

One of the next purchases will b a 180, or something.

[horvlas]

Probably Attila's opinion is true. I have also Pentacon 4/200, but it focuses beyond infinity. Somebody had opened and not built up properly. I have turn one round plus or minus the whole lens group inside! I think.