Garrett Ace 250 coil not detecting metal

[Galan46]

large piece of metal over it, it seems to detect it with the correct loud sound. It will not react to a coin-size piece of metal and by large = so connector connections are ok, probably Tx driver has a problem,
I have looked at the feeding of the TX pin 4 to the OP37G = OP37G it is a op amp so that it is a receiver.
To which IC is going another connector pin ?

Connector 2 goes to IC LM386 pin 3 by a 564k resistor. This IC has a blue cap. sitting on top. Viewed at the right top end from the coil connector. Checked the resistance and it's ok.

[Galan46]

large piece of metal over it, it seems to detect it with the correct loud sound. It will not react to a coin-size piece of metal and by large = so connector connections are ok, probably Tx driver has a problem,
I have looked at the feeding of the TX pin 4 to the OP37G = OP37G it is a op amp so that it is a receiver.
To which IC is going another connector pin ?

Connector pin 4 goes by a series cap and a 2002 marked resistor to pin 4 of 14 pin IC 140168G but I don't recognise this type of IC.

[pito]

140168G = maybe B not 8 = CD4016 SMD ( MC14016BG )

[pito]

IC LM386 pin 3 by a 564k resistor.=



there is also CD4016

It looks like you should have 3 pins connected to ground ?



5. Receiver OP376, and transmitter LM386 – no changes found.

[pito]

[kt315]

original circuit of the coil

[kt315]

[Galan46]

Thank you for all the images and support. I have verified that the Demodulator, bilateral quad switch 14016BG has 7 pins to earth as in the pic attached. Pin 7 is not showing in the diagram but the drive from the dual voltage comparator LM393 pins 1 and 7 seems to be in order. I am still none the wiser but I have now a clean sound from the speakers after I have stabilized the coil connector case and everything is tight with no spurious sounds when wiggling the coil lead or the plug, which establishes without doubt that there are no issues with the coil or the connector. Furthermore, with the detector switched on and selecting any of the programs, pressing the "pinpoint" button that I have previously mentioned, there is now the normal background low sound, and on passing a large piece of metal to no higher than 4" it does pick it up with with a high tone but no small metal reaction whatsoever, and none on any detecting mode to any size or types of metal. So there is life in this circuit and I will have to wait until my friend gets back from holiday to access his oscilloscope.