GOLDSCAN 5 SCHEMATIC QUESTION

[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

[dbanner]

Look here, at least thats on original GS5.

[Orbit]

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

[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?

[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.

[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.

[Altra]

Double check for errors!

[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 ?

[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 !

[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]

Hi Jose !
Is this version tested ?

[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

[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

[dbanner]

Bravo! Thanks for posting.

[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