well first off, when checking a 2 pole switch the wires need to be removed. When switched on if it fails to show continuity or fails to show an open circuit when switched off it has failed.
By your picture the wires in the middle are part of the internal 'light circuit' ?
Brian, it's interesting when you speak of 'lakes', for those of us from NY state always say the lake name first then 'Lake', the exception being the Great Lakes and Lake Champlain.
yep, it's been a stormy second half of the summer here SE Pa, my system has been un-plugged much more than normal. 4 1/2 inches of rain just last week.
6' of IC in that connection is too long IMO, remember the signal traveling through it is extremely low and susceptible to interference more easily than any other. FWIW my length is 1/2 meter in that run
How long is your run from your TT to your phono-pre ? The shorter the better. Your 'hum' may in fact be entering through it.
try this trick, wrap your IC (TT > phono-pre) in aluminum foil, if that eliminates it, you've found your answer ;)