I know it's 40 years later on many of these machines but it's still regrettable that the manufacturers chose plastic for many of these parts when they had to know metal (even low grade pot metal) would have lasted forever. The difference in cost per machine couldn't have been that much.
The machines being made today will be even more difficult to repair 40 years from now because there will be degraded electronics along with plastic parts to deal with.
Silver solder gets expensive quickly and melts at higher heat. It's also stronger than pewter or regular solder. Pewter doesn't have silver in it and is closer to babbitt and plumber's solder in composition.
Rodney