GOLDSCAN 5 SCHEMATIC QUESTION

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

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Audio board

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

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

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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.

[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.

[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.

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

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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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I did try to reverse engineer audio from some photos and this is as far as i got. These are the pics i got of the audio board.

[Idefix]

I have seen your post with pictures 1 to 6, so , I thought that you have a GS5.
So, with good pictures, with only 2 layers it is quite easy. See my PM.

May be you can answer to the question about the wires : (from or to Audio board)
on East side : 3 wires :1 blue / 1 White /1 Yellow . The label on board for blue is Ground. where do they go ?
On south side (the 2 pots are on S.S ), three wires plus 2 wires under the board (label Thresh ) 1/White / 1 Grey /1 Purple / They go to a POT I suppose. ?
and the 2 : 1 black / 1 green : going to main board
On North Side 4 Wires (3 with blue/Brown/orange and one Blue alone)

Are these colors the same as GS4 ?

[eclipse]

No one here has the original board. Even if he does, he preffers to remain silent, probably too much hassle to take the device apart. And reverse engineering by photos - not the brightest idea.

About the JFET orientation - I meant on the GS4 JFETS are oriented backwards (G-S are swapped on some schematics).

I'm not too worried about the sound right now, I will maybe try to create PWM based sound.

A bit more info: on the final op amp stage I'm getting 0V (no target) to ~4V (target) right now (geb channel disconnected).

Final op amp on GS4 is -4.2V (no target) to +4.2V (target) - those are the numbers I get

[Idefix]

Hi,
To Eclipse :
Would it be possible to you to take 2 pictures of the audio board, with full components, one top side, other bottom side?
And if possible , tell where the colored wires go , on the main board.
The white one , as I see , is the ground.

I will try to give a schematic.
There is the AD654, an thers is a dual opamp TL052. the other part is missing from the pictures .
Thanks

[Jose]

On the GS4 line, the issue of the possibility of inverting the source and drainage terminals was discussed, some members said that it would not be advisable.
What I can say is that a few FET can work well in GS4 or GS5, the J113 and the BF245A, also the J112, I can not recommend another.
Jose