First, label every wire you see. Put a tag next to each connector that says what it’s supposed to do, even if the label looks silly. Then, grab a multimeter and check continuity between the source and the destination. If the line is broken, you’ll see a jump in resistance; if it’s shorted, you’ll see zero ohms. Work in sections—test the power feed, then the signal feed, then the ground plane. If a wire is tangled, straighten it out, trim any excess, and secure it with a zip tie. When you’re done, redraw the circuit diagram on a fresh sheet, labeling every component. That way, if something goes wrong again, you’ll know exactly where to look.