Hello, my Rev Counter does not work and i do not know why !

I checked all wires and all colours are matching.
I could also messuered a current conduction on the rev counter wires if engine is on

On idle speed the rev counter does nothing
If i give more rpm the rev counter seems to deflect BUT in the wrong direction
It is not clear to see if it is just vaibrating beacuse of the engine or if it is pushing to the arrester and shakes becauase of that....
I belive it is not only vaibratiing cause the speedo does not

What could be wrong

Sorry for my bad english but i dont know better how to discribe it better

Today i tested another REV Counter.
One of my other bike from an XL 600 LM.
This one works so the problem is inside of my NC24 Rev Counter !

Anyone knows what could be wrong there ?!

Im sure theres someone selling one or a set on ebay as it sounds like it needs replacing, having said that if its nackered - no harm in cracking it open to see if you can find the problem :)

I am going to open it for sure !
I just thought there is a typical Problem inside which is easy to fix ?!

I looked in it for a secound only and everthig seems to be alright but i guess i have to take a closer view.

its broken

Just bought a new one ......