iPhone 7 Plus VDD_MAIN short causing no power
The main power rail can spontaneously have a capacitor short to ground from a voltage spike. The capacitor essentially becomes a wire directly to ground. When this phone first came in, it was shown to pull amperage from the battery connector from a DC power supply immediately upon connection. This usually indicates a main power rail short. After using multimeter, it is confirmed that vdd_main is short to ground. Upon inspecting each individual component on that line, it is plain to see which capacitor has gone bad.