In article <45c8qh$os0@news.gate.net>, photoman@news.gate.net says...
(..)
>Using an F-4 with two SB-25 flash units...one on the camera and the >other at the end of the 10-foot Nikon connecting cable. Both units set >on TTL. When shooting medium shots (head and shoulders or a little >farther back,) I find the negs can be extremely overexposed. (.....)

Sounds like a bad cord, a bad connection, one or both flashes set on
rear curtain synch., or you are just too close to the subject for the film speed and aperture used. You can do tests without exposing film: place a couple of inches of film over the shutter opening in the camera so the TTL flash will work properly, then try to duplicate the full-firing of one of the flashes, if that is the problem. My guess is that connectors are not fully seated, and stress occasionally causes
a bad connection (or a stressed faulty cord has the same result).
Hope this helps.