Still in the dark

[e2e]

Thanks for all the replies so far but...
I have stripped cleaned and tested the switch and dip/main assembly, there
is nothing even remotely wrong in there. Neither does the plug that goes
into it show any sign of stress/dirt/resistance at all.
I'm sure there is no supply getting to the switch other than to the main
flash which is, I assume, a separate supply.
Now I assume that the supply to the switch is one or both of the large pins
in the plug, both of which show no sign of life. Can anyone lead me back
from there to where they come from...
-- 
Sam Clarkson