I'm trying to figure out how to use an old Sunpak 611 with my Canon 6D. I have a little 90ex mounted on the camera and a Wein optical slave plugged into the 611. When I fire the camera, both strobes flash, seemingly at the same time, but the effect of the 611 isn't seen in the photo. Setting the camera's shutter at 1/30 doesn't help. Suggestions anyone?