Are you looking for a repair person nearby? Because I think fixing either machine will require taking the machine apart to some extent.
There are specialized forums for vintage Viking and Singer sewing machines at groups.yahoo.com . You might get more specialized help on those groups but, if you do not want to take the machines apart, I'm not sure they will be of much help.
In my area, if I had to take both machines in to a repair shop, the cost would likely be as much as the cost of a new sewing machine from Walmart (about $200). I would suggest just getting a new machine. Then you have all the time in the world to investigate fixing up the old ones.
Edit: I found this website with tips and schematics for the Althena:
http://www.tandtrepair.com/Athena2000.html