I just obtained a Vivitar 3500 flash bundled with some lenses I bought.

I found that the trigger voltage is between 6 - 9 volts, so safe with modern gear. It has a sync port just like the 283/285, so I figure it might make an OK hair light, for a stobist kind of setup.

However, I can't find any operational info, not any online manual.

Does anyone know where I can get this?
Any idea if this will be powerful enough for my application?

You can get a reprint of the manual for $12.00 here: http://www.photobooksonline.com/books/userbk25FU.html

Hope this helps.

Excellent.

Thanks!