Did you see this review, which a Google search threw up .....?
Vivitar 285HV Review | Popular Photography
It claims that the voltage is ok for modern DSLRs and gives a good run down on the operating processes.
It's a single pin flash, so no communication of settings information with the camera. You work the camera in Manual mode and set the appropriate aperture dependent on the selected 'vari' mode . So you have to keep well aware of all your settings to ensure good flash exposures. It has a Manual mode also with 5 power levels, 1/1 down to 1/16.
It sounds like a good solid unit. I have just started using my old AF280T again, sort of a similar thing (although it has the old TTL mode for the film cameras also), and it's actually rather enjoyable for someone who likes to juggle settings and keep a firm grip on things.....it's very satisfying to read off the required aperture on the printed scale, set that manually on an old lenses aperture ring, shoot, flash, and get a perfectly exposed image !