[Arran]

Then again if the "Mods" make zero sense, like having both ends of some component tied to chassis ground, or having one end go to nothing, or is obviously not original like added switches, jacks, or terminals, then it's probably the result of someone's meddling. It was not uncommon for new capacitors to be installed bridging old ones, this was either bad service practice, or someone was attempting to find a fault like an open cap.
Regards
Arran