I always use a multimeter to check the cable and plug before anything else. First check the cable for continuity to make sure that the cable isn’t shorted in any way. Knowing if the cable is not shorted, plug it into the socket and then check to see if is shorted in the socket by touching the tip of the cable with one end of the meter probe, and at the same time touch the shank with the other probe lead. There should be no continuity. If so, the plug is shorted to ground. Next with the cable plugged in, touch the shank of the cable with one lead and then use the other lead to touch the bridge or strings. You want to see continuity. If not, then there is a open (broken) wire from the plug to the ground circuit. Then check again by touching the tip of the cable with one lead and the bridge/string with the other. There should be no continuity (open circuit.
Good Luck…
Oh, if my explanation is a bit confusing, let me know and I’ll take photos of each step and post them here for you.
Keep on Thumpin’!
Lanny