GOLDSCAN 5 SCHEMATIC QUESTION

[Jose]

Hello Orbita
If it is tested, it is working.
There may be some involuntary error, even if doubts arise, we can compare with my prototype that is working.
Jose

[Orbit]

Does he alter iron tone „instantly“ after crossing above the iron target ?Does it work on 3khz and what is the width of the pulse ? Thank you Nenad !

[Idefix]

Here is the audio section from the TDI Pro proto-type.
.....
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

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

Hi

Many thanks for these posts. Very usefull.

Jose, about the GSX5JB, your drawings looks like using the CadStar CAO. Is it ?

[Altra]

Double check for errors!

[Davor]

...To differentiate the Turkish scheme, call it GSX5JB.
Jose[ATTACH]41051[/ATTACH]

I noticed you put D7 a normal silicon diode. It should be a Schottky. Its function is to prevent JFETs gates from conducting when forward biassed. Trouble with JFETs is that a gate-channel barrier is lightly doped, so the gate-barrier diode forward voltage is lower than that of normal silicon diodes, and therefore a normal diode can't prevent JFETs from conducting in this configuration. Try BAT85 instead.

[eclipse]

Hi

Many thanks for these posts. Very usefull.

Jose, about the GSX5JB, your drawings looks like using the CadStar CAO. Is it ?

It's DipTrace which I also use.

I noticed you put D7 a normal silicon diode. It should be a Schottky. Its function is to prevent JFETs gates from conducting when forward biassed. Trouble with JFETs is that a gate-channel barrier is lightly doped, so the gate-barrier diode forward voltage is lower than that of normal silicon diodes, and therefore a normal diode can't prevent JFETs from conducting in this configuration. Try BAT85 instead.

Davor I was working today on my Goldscan 4 board (basicly the same is this one) and didn't have BAT85, so I used 1N4148 - it works well with those. Probably it's not too critical.

Double check for errors!

U2A - the resistor between leg 1 and 3 must be 47K. The op amp UA2 is TLC2262. The capacitor between leg 1 and 3 (100nF) is 47nF

Integrator inputs are wrong.

[Altra]

U2A - the resistor between leg 1 and 3 must be 47K. The op amp UA2 is TLC2262. The capacitor between leg 1 and 3 (100nF) is 47nF

Integrator inputs are wrong.

How do you know do you have the same circuit board in front of you?

[Orbit]

Thank you, Altra ! I believe that everything is correct ...

[dbanner]

Look here, at least thats on original GS5.

[Idefix]

I noticed you put D7 a normal silicon diode. It should be a Schottky. Its function is to prevent JFETs gates from conducting when forward biassed. Trouble with JFETs is that a gate-channel barrier is lightly doped, so the gate-barrier diode forward voltage is lower than that of normal silicon diodes, and therefore a normal diode can't prevent JFETs from conducting in this configuration. Try BAT85 instead.

Also SS22 vishay diodes can be used. Vf is lower . But with 2K2 before, it is not absolutely necessary in fact. ( Looking in spice, it does not make difference. Depending on the models, sure. It is not the real life )

2K2also makes the gain half of the previous sheme.
https://www.vishay.com/docs/88748/ss22.pdf

[Orbit]

I'm completely confused dbanner so far he is looking for the diagram GS 5 and now it shows photo GS 5 ?!!

[Altra]

Eclipse is correct about the integrator inputs reversed. The integrator is a TL062, the next 4 amps same page are a quad lt1114. The audio gain stage is a LT1112. A quad TL064 is used for the absolute amplifier with one of the amps unused. I drew this for reference not to clone. If people find something they question circle it on the schematic and post. I will try to verify.

[Jose]

I noticed you put D7 a normal silicon diode. It should be a Schottky. Its function is to prevent JFETs gates from conducting when forward biassed. Trouble with JFETs is that a gate-channel barrier is lightly doped, so the gate-barrier diode forward voltage is lower than that of normal silicon diodes, and therefore a normal diode can't prevent JFETs from conducting in this configuration. Try BAT85 instead.

Thank you Davor for the observation, in all the diodes use 1N4148, I will replace them as soon as I get those diodes.
Jose

[Jose]

Hi

Many thanks for these posts. Very usefull.

Jose, about the GSX5JB, your drawings looks like using the CadStar CAO. Is it ?

It's DipTrace.

[Jose]

Does he alter iron tone „instantly“ after crossing above the iron target ?Does it work on 3khz and what is the width of the pulse ? Thank you Nenad !

Yes, high and low tones change rapidly when passing metals of different conductivity.
Press width TX use 100 useg.
The frequency, 3; 3.2 Kz
Sample 15 useg. separated 100 useg for the second sample.
Identical GB channel, the separation between both channels is 20 useg.
The points marked A, B, C, D, in my scheme, they have no relation to the Turkish scheme.
Jose