Hi ,
you are talking of the cable gland of the strobe housing or of the Nikonos plug ?
if it is the strobe housing : remove the batteries first
remove the 3 black or yellow sticks around the strobe between black and transperent boddy by using a knife then unskrew the little skrews and seperate the housing .... pay attention to the strobe tube connects there is a up tp 360 V that is enough to kill you ...... take a big isolated resitor about 10 K ohm and 10 W to discarge the capacitator ( do not short cirquit danger of explosion ) till the power is less then 12 V . Then remove the little washers holding the PCB ( use a little skrewdriver ) pay attention not to loose them . cut the little strap holding the cables together,and disconect the plug then slightly pull out the PCP ....... now you are able to fix the inside nut again ..... remount it in other way round ....... put the big o-Ring onto the transparent housing part before putting together ...... hold till all 3 skrews are mounted ....
naturaly clean all sealing surfaces befor ....... and do not forget to reconnect the synccable to the PCB .
If all is done right all will be sealed again ......
I do not take any guaranty to this manual .... you have to know wat you are doing .....
IF it is the Plug nut just fix it again and it will be OK the only difficulty is to hold the round socket ..... I use a special tool of my milling machine to do this without destroing the chrome pated surface......
sorry for my english ..... ist id rather difficult to explain tecnical things with school english .
Michael
Whilst trying to resolve an intermittent fault in the nikonos fit sync cord for my YS60 by cleaning all teh connections I unscrewed the bulkhead bolt which released the internal nut that holds the oring / bulkhead in place. Now I cant reattach the sync cord properly 
