Goldscan lV PCB

[greylourie]

I for personally welcome modifications and improvements to old designs but lets get the originals where possible fully functional as per manufactures specification first , Not just a quick fix due to lack of understanding and knowledge of how the design suppose to perform or lack of skills regarding construction.
Seen it here a few times where by components have been deleted in later designs with total disregard to there original purpose, which in my opinion is poor and not a professional example for the young up and coming engineers on here.

Another thing while on the subject which should have been implemented along time ago is, If a original design is dramatically altered from the original manufactures specification its should be named as such instead of confusing everyone with different versions, A good example of doing things correctly was the Tesoro Golden Sabre which Ivonics modified and refined and named it Tesoro Golden Sabre Light (TGSL) which I thought was fitting due to it been a lighter design because he had done away with Notch facility together with some extra refinements without destroying the original manufactures design.
A bad example which started off so well was the Famous Barracuda by Anchor Electronics a non Motion PI far ahead of its time, which if replicated identically to the original design is outstanding. But to this day for reasons I cannot understand and never been explained why the Silverdog kit was modified in such a way its working characteristics replicated the same as the Whites Surf a motion PI which is fine, but should never have been called Barracuda- anything period, because it was altered to something other than Barracuda.

Going back to the Gold Scan, Would be great if it could be sorted out to a practical working design, Been following it on/off for the last couple of years, got all the earlier diagrams etc which willing to share if they are of any help but proberly not.

Regards

Hi satdave,

Like you say, modifications can have a tendency to take away rather than enhance the performance and characteristics of the original.
The biggest diversion made with Goldscan builds, so far, has been the addition of the two resistors at identical spots in the two separate channels. This was because of complaints by builders, that the machine had a tendency to drift. And this is what completely changes the nature of the machine, as originally traced by Alexismex.

At first glance the opamp circuit driving the two J113's, is used to quickly reset the machine when large signals are detected. But when trawling the internet I came across VCR's. Was that particular pair of J113's intended to have a dual purpose of both quickly resetting and/or maintaining stability. By providing some kind of feedback driven voltage controlled resistance for bleeding to ground ?

Jose' did report getting a marked increase in sensitivity when he altered the value of the resistor that follows after the opamp that controls those two particular fets.
It would be nice to hear feedback on how others think it should operate.

As to original or modified...... your example of ivconics TGSL is great.
Construction of a clone Goldscan would be best left for accomplished and competent builders, as correctly adjusting the setup could prove tortuous for the novice.
Whereas, a modified version could be easier to construct and setup. And could quite likely (if done right), be better performing and simpler to use.


I'm glad that some interest is being generated.

[greylourie]

Hi All,

I managed to get the Goldscan PCB to load up in 7.8 it was a path issue when I was opening the file it kept defaulting to "untitled.lyt" so was struggling to open the file..!
So before I get some PCB's made can someone verify that this is the most up to date version please..?

Hi Dean,

No one has posted a proven build using those schematics. And if pictures posted in threads somewhere here on Geotech are anything to go by, of the original pcb, the version you have does not look like it has been properly laid out.

I'm sorry if, (in my enthusiasm) over on the Delta Pulse thread I suggested you look at the Goldscan as a potential candidate for a build - but the fact is that there has not yet been posted a confirmed and bug-free pcb design.

We need some gurus to come in, on the act.

[greylourie]

I have an original Goldscan 4. Only Coil and Battery is not original. So i can messure some part´s and make photo´s if something is necessary. The depht in normal mode without GB and Disc is very good. But with GB and Disc it lost a good part. But this could be because the homebuilt coil and wrong adjustments of the internal controls.

Hi mschmahl,

If you are willing to open up your original goldscan main box and confirm the layout and values of some components I would be most greatful. I have posted a section of schematic below, in .png format.

If you could confirm the presence/value or absence of the 470K resistors that are circled in red. It would be interesting to see if they have been added to your original.
If you could measure/confirm the value of resistors,caps in the blue box. Also please confirm the value of C28/C29, both have value of 470nF in the schematic.
If you could tell us the value of the capacitor that is missing from the schematic. I have circled the area in purple/violet. It is part of the filter/clipping diode circuit connected to feedback pins of U13:B opamp.

In original photos posted by Alexismex, there is a resistor network chip that is also near U13. It is very difficult to follow traces in the photos that have been posted, as the angle and resolution is not clear enough. If you are willing, could you possibly trace and confirm the connections for that RN chip. If it is too awkward, do not worry, as Jose' has posted a working alternative.

If you could take clear and good top-view photos of the main pcb, with the connecting wires laid away from the board.... Possibly photograph it in sections.Then we would have a good source of reference for track and component layout, to work from and use as a basis for a Geotech version.


If you could do any or all of the above, and post it up here on Geotech, it would serve the community greatly. That way, anyone (gurus included) have a point of reference to go forward from.

Regards

Jon.

[scs]

This detector discriminate only gold-not discriminate for silver=

[greylourie]

This detector discriminate only gold-not discriminate for silver=

I think somehow your reply is wrong.
Maybe depends on how it is setup.......

[mschmahl]

Hi mschmahl,

If you are willing to open up your original goldscan main box and confirm the layout and values of some components I would be most greatful. I have posted a section of schematic below, in .png format.

If you could confirm the presence/value or absence of the 470K resistors that are circled in red. It would be interesting to see if they have been added to your original.
These two resistors are a mod from reg. They are not installed in the original. With these resistors the original GS get a sort of SAT. If you have 470 k for both or less you get a fast SAT. If you use higher resistors (1M or 2M) you get a longer Satspeed and a bit more depth than with the 470k´s. With this mod installed you don´t need the reset button. Without this mod the GS is a little deeper but you have to push the reset button once in a minute.

If you could measure/confirm the value of resistors,caps in the blue box. Also please confirm the value of C28/C29, both have value of 470nF in the schematic.
this i will confirm tomorrow.
If you could tell us the value of the capacitor that is missing from the schematic.
I think there isn´t a capacitor. But i will see also tomorrow.
I have circled the area in purple/violet. It is part of the filter/clipping diode circuit connected to feedback pins of U13:B opamp.

In original photos posted by Alexismex, there is a resistor network chip that is also near U13. It is very difficult to follow traces in the photos that have been posted, as the angle and resolution is not clear enough. If you are willing, could you possibly trace and confirm the connections for that RN chip. If it is too awkward, do not worry, as Jose' has posted a working alternative.

If you could take clear and good top-view photos of the main pcb, with the connecting wires laid away from the board.... Possibly photograph it in sections.Then we would have a good source of reference for track and component layout, to work from and use as a basis for a Geotech version.


If you could do any or all of the above, and post it up here on Geotech, it would serve the community greatly. That way, anyone (gurus included) have a point of reference to go forward from.

Regards

Jon.

The best schematic that i have found is this here

So are the components built on the original gs. I don´t have found a failure.

[mschmahl]

Hi mschmahl,


If you could tell us the value of the capacitor that is missing from the schematic. I have circled the area in purple/violet. It is part of the filter/clipping diode circuit connected to feedback pins of U13:B opamp.

In original photos posted by Alexismex, there is a resistor network chip that is also near U13. It is very difficult to follow traces in the photos that have been posted, as the angle and resolution is not clear enough. If you are willing, could you possibly trace and confirm the connections for that RN chip.

[ATTACH]30475[/ATTACH]

Let us look in your purple/violet area. The description of the parts is from your posted picture.

The missing cap is a 1nF Cap (1000, 63, Wima, D2), the same how c36 on your picture . The resistor network is with 10 pins, it exist 5x10k resistors. Pin 1+2 is R57, Pin 3+4 is R59, Pin 5+6 is R58, Pin 7+8 is R60 and Pin 9+10 is R63.
Pin 1 is connected with Pin 1 from U13(TL064), Pin 2, 4 and 5 is connected with Pin 6 of U13, Pin 3 and 7 are connected with the upper diode D14 (OA85), Pin 6 is connected with the lower diode D15 (OA85). Pin 8 and 10 are connected to Pin 9 of U13 and Pin 10 of the resistor network is connected to Pin 8 of U13.

[Orbit]

for sale and copy it .

[greylourie]

Let us look in your purple/violet area. The description of the parts is from your posted picture.

The missing cap is a 1nF Cap (1000, 63, Wima, D2), the same how c36 on your picture . The resistor network is with 10 pins, it exist 5x10k resistors. Pin 1+2 is R57, Pin 3+4 is R59, Pin 5+6 is R58, Pin 7+8 is R60 and Pin 9+10 is R63.
Pin 1 is connected with Pin 1 from U13(TL064), Pin 2, 4 and 5 is connected with Pin 6 of U13, Pin 3 and 7 are connected with the upper diode D14 (OA85), Pin 6 is connected with the lower diode D15 (OA85). Pin 8 and 10 are connected to Pin 9 of U13 and Pin 10 of the resistor network is connected to Pin 8 of U13.

Thanks for documenting the above details. This gives all interested members of Geotech a good point of reference.

With solid confirmation of the presence of the 1nF filter cap from your photos and examination of an original board, it can be placed on schematic. Looking at your photos the cap is connected to pin 6 (on bottom side of board) and pin 7 (on the top side of board), of U13.

I am attaching image showing connections.

Once again, thank you.

[mschmahl]

Yes, this is the correct place for the cap.

The 470k-Mod (SAT) changes the behavior of the original Goldscan much. So the gs become to a motion detector from a static detector. It is similar to that how satdaveuk wrote about the baracuda.

[greylourie]

I would be interested to know the value of R51, on your original pcb board. The value of R51 and the correct setting of the elements associated with it, could have some influence on the need for the 470K-Mod.

[mschmahl]

Hi mschmahl,

If you could measure/confirm the value of resistors,caps in the blue box. Also please confirm the value of C28/C29, both have value of 470nF in the schematic.

C28 and C29 are 470 nF (0,47, 50, Wima, C.
RV4 is a 5k trimmer (4,84K measured), R48 1M (from colorlines), R40 47k (from colorlines), R51 220k (217 k measured), C34 470nF (0,47, 50 Wima, B4), D10 and D11 are BAT85

The orange wire goes to Reset button also the black. The black from Reset goes to one Pin on the Hold switch and the brown wire goes to the other pin on holdswitch.

[mschmahl]

The backside with 2x 680k SMD installed from me for the SAT-Mod (instead of 470k)

[greylourie]

Thanks for the continued info. This seems to clear-up any doubt about schematic values. I cannot think of any posts in the builders threads, that would make me think of any other values or connections requiring verification. Your posts with info and photos are very helpful.

We can now conclude that with the addition of the capacitor at U13, the schematics should be considered as good. Hopefully they will be taken up by someone with the skill to layout a pcb. Or in the case of someone more adventurous, be used as a basis for further improvement and refinement.

I know I have said this before, but posts from people like Reg, Jose' and Max offer a lot of encouragement for the simplification and improvement over the original.

The SMD SAT-Mod addition is a very neat job. I like the way you have managed to mount the resistors over the two ring-guards. I wish I could be as skillful. Excellent work !

[mschmahl]

I have disconnected the SAT-Mod. Now the possibility to ignore iron is much better and lacking of depth is not so much as with the SAT-Mod. But the complete GS is very noisy, you can´t seldom get a constant treshold. I have it to try it outside.