[kruc]

I don't trust the solder joints in these old chassis. They were made by unskilled assemblers using megawat welding irons with solder of a lower quality than is available today. An iron that size is only needed when it's necessary to resolder a grounded lead on the chassis. Old oxidized solder joints aren't a problem: add flux and suck the old solder off, then add flux and resolder it with 63/37. I bought a huge iron a few years ago at a garage sale but haven't found anything yet I couldn't do with a 30w iron. Get a bottle of rosin flux for about $8 and start using it. When you see how much better your joints turn out you'll never solder without flux again.
Dave