Owned this faithful workhorse for over 20 years. Pre ignition key operated dash glow coil playing up. 'Repairman installed button to get started until I purchased new one. Coil left dangling. Button loose so being able to start tractorintermittent. Decided to tighten nut behind dash holding the button. Spanner must have bridged + and - as loud noise and all electrics dead. Two fuses under air filter not blown and ok. Cannot locate any fuse on battery to starter cable. Advice appreciated as to what to look for and check.