MZ5n shutter wont fire

I think my MZ5n has finally bit the dust , I was going to put a film through it but despite a fresh set of batteries when I press the shutter all I get is a whining noise, trying the DoF preview gets the same noise, sounds like its something to do with stopping the lens down prior to shutter release.
The Auto-Focus works OK as does everything else.

Suggestions anyone? apart from bin it or sell it for spares

PS the batteries are OK in my MZ7 so its not those.