GOLDSCAN 5 SCHEMATIC QUESTION

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Here is sprint file of incomplete audio board. I worked out the wires and where they come from.

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Eclipse, don't you mean drain and source?, you stated Gate and Source(G and S).

[eclipse]

Yes my bad.
Im guessing when i turn on the geb channel voltage will swing below 0v, GND being default level and depending on which channel has stronger signal will go above or below 0v. Confirm this when you reach that point. (As i said earlier Gs4 final op amp is at -4.2v when no signal going positive up to +4.2v if there is a target so this gives some perspective over the changes being done GS4/GS5.

In this photo I can see what appears to be TL052 http://www.geotech1.com/forums/attac...6&d=1511385505
It's in the audio pcb, which is not drawn in the PDF schematic, and the one marked TL052 in the schematic is TLC2262.

[Idefix]

Hi
TL052 and TLC2262 are twice opamps , pin compatible.
But, the TL052 requires its supplies rails to have minimum +5V and -5V. up to +15 / -15V.
The TL 2262, is a CMOS one, requiring only +4.4 v between the rails. So, the TL052 is used at the edge of the specification. I mean that is the reason why some peoples uses +6v/-6v instead of +5V/-5V in the board they build. The 2262is also slower, but in audio amplifier with not too much amplification, it is not an issue.

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Very good knowlege. Can someone please explain to me how the jfets are supposed to work in this circuit. Are they normally in an "on" state, allowing nothing to pass, and then only when something is detected do they switch, allowing signal to pass on. Therefore detector runs silent when nothing is detected?
Heres my power supply layout.

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I can understand switching the ground balance channel in and out, but the other two jfets?

[Jose]

Although my knowledge of the subject is elementary or basic, I will try to explain what happens in this circuit.
The Fets are normally open.
In most PI detectors, when a metal object passes under the coil, they produce two signals. a first positive signal, then a negative one.
The other signal, the negative, is suppressed by the Fets and the circuits associated in both channels.
This is what happens in most of Eric Foster's detectors.
Reg referred to this topic in the GS4 forum.
The third Fets, capacitor discharge of 0.47 mF. This capacitor is part of a filter, next to the resistance of 5.6 M. There is another filter later and I would not know how to specify its function.
Jose

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Thanks for explanation. I'll have a read again GS4 threads.

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Audio board

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Now I begin construction. Maybe this is too ambitious for me? But I''l give it a go.

[Altra]

Here is the audio section from the TDI Pro proto-type. I did not publish before, but White recently announced that this model is now discontinued. This was reversed from a prototype unit, so I assume many changes and improvements were made to the more current units. It should be very close to the last GS5 and will match up to the incomplete schematic on Geotech. Whites added a LM386 amplifier to drive a speaker. I added the Hi/Lo tone switch which was not on the prototype.

I bread boarded the circuit using a CD4046 instead of the AD654. Also used 2N2222's for the npn's and PN2907's for the pnp's.

Probably some mistakes, but easier than looking at photos

[dbanner]

Bravo! Thanks for posting.

[Jose]

Thanks Altra for posting.
Some time ago, I came to the conclusion that it is the same audio as the CS7 Scope, looking at some images, but multiplied by two logically.
We can say that part of the GS5 audio, we had in front of our noses all the time.
I have a similar prototype worked, but this is more complete.
The first part of the GS5, you have some errors, I will publish my version that is tested and works in a next post.
Jose

[Jose]

The first part of the GS5 scheme has errors.
What I am publishing, is my version based on the Turkish scheme but with the corrected errors.
It may be something different, but it is working.
To differentiate the Turkish scheme, call it GSX5JB.
Jose

[Orbit]

Hi Jose !
Is this version tested ?