TR4 strange wave form1

[olecram1]

Hello.I have set up my tgsl from the pcb and I have found a very poor detection level. It is only sensitive to large parts and less than 4 inches. The oscilloscope displays everything in order except for the tr4. The wave is strange and does not change when turning Disc potentiometer. I hope you can help me, thank you.

[olecram1]

I´m sorry. I do not see j3 at schematic, i doit and now is better. Thank´s.