Sanwa Flash question

So I have a Sanwa Flash laying around my house. I read that it has a 3pin adapter for 5v and I wanted to wire it up to a PS1 dual shock.

My problem is, the PS1 pcb only has 3.3v and 7v and I am unsure as to which I should wire the Flash too.

Thanks.

use this http://www.tekgear.com/index.cfm?pageID=90&prodid=466&section=73. works for me with no problem

hello