Hi there,go through your rig and look for any piece of gear that is 2-prong unpolarized ( 2-prongs the same width in dia.) or any piece with a "polarity" sw. or has the Gnd.pin removed.Disconnect the signal path from all the pieces,power them up and measure the AC volts between the chassis'.Flip the "polarity"sw.till you get close to 0 volts AC.Connect the signal path and you should be ok.Good luck,Mel.
