The old Reliant, Cooperheat, etc. all used resistance heat. In most cases, the power supplies were 80 vac or 80 vdc and were also used for grid welding systems, such as the Miller GPS1500's. All of these are still around including contactor boxes, chart recorders, heating blankets, and so forth. Let me know if we can help. weldersales
Also, all the Powcons, from 200 amp to 550 amp are still very much alive and available as well as repair parts.