Homemade metal detector.

Friends! I took apart the underwater metal detector that my friend brought to me. The metal detector is made on the NE555 microcontroller and on the Soviet k157ud2 chip. During the repair, I noticed that the NE555 is damaged, I believe that moisture entered the chip, which led to failure. The metal detector is equipped with a light and vibration indication with a separate power supply for a DC motor with an eccentric that creates beats when rotating. The most interesting for me was the method of converting