Today I lubricated, adjusted and cleaned a 403a. The process went as described above, but the upper thread broke often and a clicking sound presented itself. Change of needle remedied the click, but upper thread still snapped often. I work under the impression if not broke don't fix it, but the last remedy available had to be the tension. Unassembly revealed a rust spot on all thee disks. Cleaning remedied the problem. I did have to lower the bobbin tension along with the upper tension to get a consistent stitch.
Earlier, I neglected to mention I rewire or purchase controllers if needed. I also didn't answer if I'd purchase from a reconditioner. I probably would not as I believe I can recondition a machine as well as the next person.