On an old Bally I would have thought it more likely to be a faulty coil, or if you are lucky a break in the wire near the lugs. The hold coil is the fine wire. Faulty EOS on a Bally means the coil will not fire (EOS no contact at rest, broken wire leading to EOS) or will blow the fuse (EOS never opens when flipper activates).
cheers
Ian
