The solution is not exactly correct, don't drill a hole to the DIN connector and don't isolate ground connection.
- Just unsolder black wire and the ground pin from the left negative pin and blue wire.
- Solder the black wire to the ground pin. The ground pin on DIN connector is the one in between channels, between green and blue. It needs to be connected to the arm body, that's why there is a metal plate soldered to it. Normally it aligns with the screw hole seen in the picture above and screw ensures electrical connection between ground pin and tonearm body.