After many years of use and abuse my FT 817 experienced a problem—it would work on the internal battery but not from an external source connected to the power connector.
After some time spent looking at the schematic and the radio, I discovered a break in a pcb track, close to the power connector. It would seem that when used regularly for /P operation, where the external power connector is repeatedly inserted/ pulled out creates mechanical stress on the pcb causing a track to go open circuit.
The fix is a simple, though delicate, matter of making a solder bridge across the pcb track.
Having made the fix, I mentioned it on air to Rob–G4RQJ who says he and others have experienced the same problem. Portable operators of FT 817’s take note.
Best wishes Gordon G0EWN