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"It is strange that no one should have such a device."
I an unsure what you mean.
If you are surprised that no-one else replied with an answer, I should point out:

* Your English is poor, many people will not understand your original question.

* Your question is highly technical, about the electronic innards of a detector. People on here USE detectors, they don't build them, repair them, modify them electronically. You should register with the technical Geotech1 Forum, where you might get some response.

*I am sure there are many people on here who own a G2 / F19 / Goldbug Pro / or a clone. But they are not going to dismantle their detector to answer your question, for a multitude of reasons.
Here is the Geotech1 Forum that I recommend joining:

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People are even less likely to open their machine now, as we have determined that very few machines actually have this part fitted on the PCB. Perhaps only very early models had these mystery components.

Here is another good photo, located here on this forum:
As you see, the parts are not fitted

An F19 WITH the parts fitted, but hard to read:
F19 with parts fitted

Try and work out the pinout of the missing part. Is it connected to the same power supplies as parts U1 and U2, which I think may be op-amps ? Or is it connected to logic voltages, perhaps the same supply as the PIC microcontroller?
Single analog switches normally have a standard pin configuration, for example see here:
single switch SOT23-5

Likewise, op-amps also have a common pinout:
single opamp
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amazing photo. but the inscription is invisible. q2 are transistor pumps tx. I found a diagram on the Internet, from tx850. but there is also no u7. wrote wherever possible). Only you help. Thank you very much. 


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I saw the thread on the Geotech1 forum.
Advice : Try not to argue with Carl, he knows what he is doing.

So I think my earlier advice about removing the two / three capacitors and resistor may be a solution. If it does not work, re-fit them, and purchase the XOR gate IC.
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The XOR gate is used as a digital mixer. The digital output is low-pass filtered, to give a DC voltage. This DC voltage varies as the phase relationship between the two logic inputs varies.

It is a common part of a phase-locked loop ( PLL ) circuit, for example the CMOS CD4046, which has 3 choices of phase comparator.
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