I do not know what kind of solder was used in older machines. Only way I see soldering being a problem is if Low-Temp (aka soft solder) was used. Regular solder and Hi-Temp solder would not be an issue. Soldering makes for a very good electrical connection. In that it is electrically conductive around wire (even through stranded wires), does not suffer from loosening due temperature changes, does not carbonize, and stands up to harsh environment (outdoor usage).