Hello,
While soldering, a common issue that I sometimes face is that the cored solder wire that I use, sometimes comes without flux inside the core. Like the core is empty.
Now of course,this is an issue as no flux could result in bad soldering welds, and other problems in general, and also the problem cannot be diagnosed without using the solder wire itself.
I was wondering if anyone over here faces the same issue, and if so, do you have any tips/methods that you use to diagnose these "bad wires"..??
Thanks 
