TESORO GOLDEN SABRE

[simonbaker]

R40

Another question for the experts:

R40 100K is mysterious to me. It connects output of comparators U106 (after diode D12) back to non-inverting input of comparator U106b (ground bal channel).

It causes clipping of the comparators output to near ground (actually near the non-inverting input which is the output of LM308 ).

I see similar thing on Amigo II circuit. What is the purpose? Why clip to LM308 output instead just ground for example?

Regards,

-SB

[simonbaker]

Another method is to set the ground balance control to mid-position, and adjust the coils to achieve minimum voltage, while monitoring the output of the sample gate in the ground channel. This will automatically give you the correct phase shift between TX and RX. In this case, you only need a single-channel scope, or a meter.

Hi Qiaozhi, Max, Ivconic - can you explain how iron discrimination works with TGSL?

In my circuit, as I turn discrimination pot, discrimination order is:

foil, nickel, penny, dime/quarter, iron.

So I can't use discrim pot to knock out iron and keep others.

Instead, I turn Ground Balance until iron goes away. But then it is gone even for All-Metal mode.

I'm confused on this. How should it work?

Thanks,

-Sb

[Qiaozhi]

Hi Ivconic,
I posted that data: it's about 200° out of phase for original coils.

In the Qiaozhi's picture (of a 9x8'' coil) you see it very clear.

That's the phase, I got the same both on my 9x8'' and an 8'' round.

But still some problem exist on larger coils... expecially DD like.
Iron detection is better avoided in CC than DD... the flux shape is a problem for near iron, I noticed that even at right phase some large coils show that iron detection at overlap area when target is huge or too near the overlap.

Kind regards,
Max

Another method is to set the ground balance control to mid-position, and adjust the coils to achieve minimum voltage, while monitoring the output of the sample gate in the ground channel. This will automatically give you the correct phase shift between TX and RX. In this case, you only need a single-channel scope, or a meter.

[rdec4]

Thanks for the response Max.

I'll ask.
Why not adjust the small phase difference in making individual coils from the electronics? There phase rotating block.

In the same work, the same number of turn and the same base for the coils and length: (), the difference in phase will be reset at very small.

I guess the difference in phase in individual coils is only a few degrees, which can be adjusted by the RC chains and set the range for regulating the discriminator and ground balance.

Regards,
rdec4

[Max]

ivconic, Max, simonbaker,

In what limit to 200 degrees change phase in your setup coil?

Should not be more than a few degrees and they should not have a significant impact on the depth, but only on discrimination and ground balance. They have to potentiometers for tuning.
Or wrong?

Why not set the correct phase of RC circuits, the output of the generator and the entrance to the receiver?

Hi,
that phase will not influence performance in air at all-metal: it influences your ability to get a good ground balance and a reliable discrimination.

So, if you are doing air tests in all-metal you'll not see anything wrong with also really different phase shift.

But when on soil... or when try to disc stuff you'll be surprised how bad it could be.

The critical adj is at coil... you null coil but search right phase also... so it's not trivial task and require enormous patience and a number of efforts to do it perfect.

I guess maybe at Tesoro as in other places they have a procedure to do that with few efforts... but usually you get average coils this way, at the end.

Sure not performative as the ones proposed here... but all factory made have excelent phase alignment to do geb and disc the right way: Tesoro is famous for reliable iron disc and discrimination stuff... not a case.

Kind regards,
Max

[rdec4]

ivconic, Max, simonbaker,

In what limit to 200 degrees change phase in your setup coil?

Should not be more than a few degrees and they should not have a significant impact on the depth, but only on discrimination and ground balance. They have to potentiometers for tuning.
Or wrong?

Why not set the correct phase of RC circuits, the output of the generator and the entrance to the receiver?

[ivconic]

Nice arrangement Driscoll !
Wise move to add audio mod on it. It will work much louder and smoother, i guarantee.
I will use this pcb in my next work..
Regards!

[ivconic]

Hung Chang 3502 , made in Korea. Pretty good for my needs. 2x20MHz.
It is old model but this one is like brand new, almost never used. Works the same as it was made yesterday. Focus is excellent.
It is expensive here also. Yet i have seen few on e-bay for $400-500 and one even goes for $800 !
Simillar one in shop here costs arround 700e !!!! To much!
Other hand, one cahnnel's are cheap..usually 200e if new and less than 100e if used and old... Recently i got offer to buy obsolete one for 30e !? Ha,ha,ha!!!

Yes Max, now i remember! Huh, i forgot, thanks!

[simonbaker]

Hi,
don't know why you have such poor results... but 15cm on a quater is really few stuff, device is much more sensitive.

Kind regards,
Max

Right now much noise because only prototype -- I hope to make it much better. I need to get a Euro coin to compare depth .

I have problem with iron -- can you explain? My tests show that discriminator circuit does not reject iron, because phase beyond silver. Instead Ground Balance pot is adjusted to reject iron. But if Ground Balance adjusted to reject iron, All-Metal mode cannot detect it either.

See my tests here: https://www.geotech1.com/thuntings/s...ad.php?t=14645

Regards,

-SB

[simonbaker]

Hi,

Added corrections from the last IVCONIC schematic (BD140).

[ATTACH]6620[/ATTACH]

[ATTACH]6621[/ATTACH]
Regards

Does the battery check work for this PCB? If not, there are more resistors you can remove, everything connected to U107b op amp.

-SB

[driscoll]

Hi,

Added corrections from the last IVCONIC schematic (BD140).



TGS last mods.zip
Regards

[Max]

"...Problem is phase... always...

At very strong null phase variations are often too far from expected value. That's real pain getting 1mV null but missing required phase angle. Have to unglue coil again and null at higher voltage..."

Ha,ha! You got that right Max! I agree 100%.
That's why i finally got scope!
Actually is not an issue to null coil at minimum residual voltage, but problem is to maintain proper phase at RX. Without scope is just illusion or a lot of hard labour, as it was in my case till few days ago...sheesh!
Sooner or later man will face the phase problem, like i did. My coils works fantastic on "coloured" items, but choking to much iron and alloys...all those due unproper phase adjusted with them.
Final question is; what should be the most proper phase shift on TGSL coil?
I dont have a clue; i had never seen or experienced any original TGS so far..!? Shame...

Hi Ivconic,
I posted that data: it's about 200° out of phase for original coils.

In the Qiaozhi's picture (of a 9x8'' coil) you see it very clear.

That's the phase, I got the same both on my 9x8'' and an 8'' round.

But still some problem exist on larger coils... expecially DD like.
Iron detection is better avoided in CC than DD... the flux shape is a problem for near iron, I noticed that even at right phase some large coils show that iron detection at overlap area when target is huge or too near the overlap.

Kind regards,
Max

[tiktak]

Hi,

Hi,
I am agree.Thats why I am also trying to get one.But the 2-chanel onece are too expencive for me.What is yours Ivica?
Because the picture is not so good.
Thanks

p.s.I am shore that you will find the source of that noise with that scope.

[ivconic]

"...Problem is phase... always...

At very strong null phase variations are often too far from expected value. That's real pain getting 1mV null but missing required phase angle. Have to unglue coil again and null at higher voltage..."

Ha,ha! You got that right Max! I agree 100%.
That's why i finally got scope!
Actually is not an issue to null coil at minimum residual voltage, but problem is to maintain proper phase at RX. Without scope is just illusion or a lot of hard labour, as it was in my case till few days ago...sheesh!
Sooner or later man will face the phase problem, like i did. My coils works fantastic on "coloured" items, but choking to much iron and alloys...all those due unproper phase adjusted with them.
Final question is; what should be the most proper phase shift on TGSL coil?
I dont have a clue; i had never seen or experienced any original TGS so far..!? Shame...

[Max]

How many voltage on lf353 pin 7 equal 1mv on rx coil?

Hi,
it's 43.13mV.
(not considering internal offset...)

Kind regards,
Max