In this post, we will discuss the famous Metal detector PI Polonese (PI polonese AFRICA V4). The original device has been modified so that some parts have been removed and others have been merged.
The important changes are:
1- Remove LF357 and uA741 and are replaced by TL074.
2- The mosfet BF254 is replaced by Transistor BC337
3- The coil inductance is tunned to 680uH.
After assembly, the device will look like this