PS I would also clean accurately the flash contacts on the flash and on the camera, after many years of non use there can be a thin oxidation layer that prevents proper work. Alcohol and energetic brush if necessary should do the trick. Same treatment for battery contacts.
It's a great flash for manual work - gives half stops to 1/16 - plus compensation for diffusers. Put it on an X700 or X570 and it's a TTL flash as good as any. It's my favourite by far out of Vivitar 283, Canon 540EZ and Minolta 360PX.