sb-600 problem

[ShutterSpeed]

my trusty old sb600 has given me a slight problem..nothing substantial. I can perform all zoom function except the maximum zoom at 85mm. Which is makes some sort of sound and then disables. I can resolve this temporarily by resetting the flash, but without capability of zooming up to 85mm. Thoughts?

 

[KmH]

It is malfunctioning, and needs to be repaired if you want full functionality.