Silver solder

Auburn, If the solder has flux in it and it's dried up then the solder would not flow correctly. When I first started out repairing radios I was using someone's left over solder from years earlier and kept having trouble with the solder joints "looking good". I asked an experienced tech and we talked about what I was using. Well he informed me that the rosin flux had dried up and not working properly.



After switching over to a new tube of solder then the problems with the bad solder joints disappeared. Most solders have either a rosin core or acid core. The acid core solder is some nasty stuff. As far as I know all solders have some kind of flux added.
That's all I got...