TGSL Tuning & troubleshooting

[Stefano]

I have BF245 too, and one more thing: I do not have 1% resistors on the RX preamplifier and I didn't match them.
Is it important to have 1% resistor there? I've seen that all tesoro schematics uses 1% there...
Can it be a reason for weak sensibility?

[Pompey]

Hi,Stefano!It`s probably coil problem to get deepest rezults with TGSL.I hardly detect 1 euro at 28sm .Coil is 5,9/6,7mH As Ivconic said Rx at this case should be 6,2,not 6,7mH.I`ll make for Rx another coil with 6,2mH. And also I ordered original fet`s J107.I found that J107 is very different from BF245.Yesterday I get two J107 from Poland and I`ll put them on the PCB tomorrow and check with another coil for Rx.I think there must be more depth.

[Stefano]

Hi.
My 2 cents of knowledge on the subject are:
TGSL runs at 14.5-14.7 kHz in Motion only mode both in all metal and discrimination. Single tone Id.
As far as I know it has not been improved from the original Golgen Sabre (apart maybe of the different audio stage) but made it lighter (removed the battery check and the whole notch circuitry).
There are however, buried in the huge "Tesoro Golden Sabre" thread, version same as the original one ( including notch), variants with modified audio with monastable circuit, and pinpoint option.
TGSL should be, I think, a reliable project since it has come to a "final release" (published on http://www.geotech1.com/forums/showthread.php?t=15710) and been build by lot of people here, with different results: some (including me till now), claiming to be not able to get more than 20 cm on 1 euro coin, others getting 30 cm and more.
It seems that the secrets rely on the coil handicraft.
About me I've just made the 2 coils as per the recipe given, but not had time yet to test them.

[Math]

hi, i just found the TGSL thread and would like to build one as my first project it looks very good but i cant find a description about it anywhere~ does it run at 15khz like the gold sabre plus but without the all metal nonmotion mode, notch and tone id~ similar to the original silver sabre? and could you let me know how has it been improved over the original design, thanks

[Qiaozhi]

Hi Qiaozhi, thanks for replying.
Today I 've been back to my shack to re-check coil measurement but my homemade LRF meter gave absolutely inconsistent data, so the value I gave can have been wrong since the beginning either because of my instrument isn't as good as I hoped, or because I swept the readings when i wrote them down.
Anyway I've tried to swap the coils connection but with no good result.
If no other clues to investigate, I'll try a.s.a.p. to build a 10" DD coil as per the given recipe on TGSL thread...

Hi Stefano,

All of the Tesoro coils I have seen use the same color coding, so your coil wiring is probably correct.

[Stefano]

Hi Qiaozhi, thanks for replying.
Today I 've been back to my shack to re-check coil measurement but my homemade LRF meter gave absolutely inconsistent data, so the value I gave can have been wrong since the beginning either because of my instrument isn't as good as I hoped, or because I swept the readings when i wrote them down.
Anyway I've tried to swap the coils connection but with no good result.
If no other clues to investigate, I'll try a.s.a.p. to build a 10" DD coil as per the given recipe on TGSL thread...

[porkluvr]

Correct

I don't think I own 2 coils with wrong colours wiring inside the coil, so I've connected: orange as hot tx side, screen to Gnd, Grey and Purple as rx coil...

That would be a statistically valid argument, except that you are comparing two different models of coils. I think you would have to be one very savy technician to be an authority on the wire color codes of different Tesoro coil models!

And you did say that your frequency was low.

I don't know how they could have gotten that way but it seems to me the inductance values that you gave are backwards from what they are supposed to be.

I can't guarantee that swapping the coils will make everything turn out right, but if you do have a 6.57mH coil connected to the transmitter and a 5.97mH coil connected to the receiver, I can guarantee that swapping them will raise your transmit frequency.

You should not be so concerned with wire colors. Be concerned with using the correct component values. What makes you so sure that the same wire color code was followed when the two different models were constructed?

Never mind, I don't want to know. Be unreasonable.

[Qiaozhi]

Yes, I got it, but I'm using ORIGINAL coils and I DO connect coils as per their original colors... I don't think I own 2 coils with wrong colours wiring inside the coil, so I've connected: orange as hot tx side, screen to Gnd, Grey and Purple as rx coil...

I would recheck your inductance measurements. The RX coil should have a larger inductance than the TX.

[Stefano]

It looks like you are trying to say that the receiver coil is 5.97mH and the transmit coil is 6.57mH. Correct?

Correct

What I really meant was that the transmit and the receive coils need to be swapped. I don't mean swap the receiver coil leads. I mean, connect the 6.57mH coil to receive and connect the 5.97mH coil to transmit.

Yes, I got it, but I'm using ORIGINAL coils and I DO connect coils as per their original colors... I don't think I own 2 coils with wrong colours wiring inside the coil, so I've connected: orange as hot tx side, screen to Gnd, Grey and Purple as rx coil...

[porkluvr]

With standard I mean around 20 ohms the rx and tx resistance (I don't remember exactly) but I remember exactly 5.97 mH and 6.57 mH measured with the homebuilt LCF meter project published on Elektor.

It looks like you are trying to say that the receiver coil is 5.97mH and the transmit coil is 6.57mH. Correct?

I think you meant mH, not uH.

What I really meant was that the transmit and the receive coils need to be swapped. I don't mean swap the receiver coil leads. I mean, connect the 6.57mH coil to receive and connect the 5.97mH coil to transmit.

Jeez, Louise.

[Stefano]

Two more scope images:
The tx and rx signals at the polo coil when connected to the Conquistador md. It is clear that Conquistador frequency is 10kHz....

[Stefano]

I've checked components and everything seems ok.
In the meantime I've borrowed an old WORKING Tesoro COnquistador.
Well, I've connected its 8" concentric polo coil to my TGSL circuit and these are the signals I got from this coil.
The coil works, and once geb is adjusted it does discriminate. I get ALWAYS a single tone for each target sweep.
The sensibility is anyway VERY POOR (well, it's not much better on the original COnquistador detector) but the coil is nulled VERY WELL (around 4mV p/p)
What I find strange is that the phase shift between the signal IS NOT 200 nor 20 degrees, but the circuit works ok (apart of the sensitivity isuue)!!!
Beware of that input are AC.

[Qiaozhi]

Is it the same with any coil or DD only?

It's the same with a concentric coil.

What do you mean with "with this design". Can you completely reject large iron with the other Tesor projects present on this forum like Bandido or Eldorado?

Unfortunately large iron will always break through.

I'll check this part a.s.a.p. however I have not completely clear how it works

First check that all the component values are correct.

[Stefano]

If you move a coin very close to the coil then a double-blip can be expected.

Is it the same with any coil or DD only?

Also, you cannot completely reject large iron with this design

What do you mean with "with this design". Can you completely reject large iron with the other Tesor projects present on this forum like Bandido or Eldorado?

Perhaps you have a problem further along between the synchronous demodulator outputs and the audio input.

I'll check this part a.s.a.p. however I have not completely clear how it works

[Qiaozhi]

I've checked components around pre-amp and they're ok.
So I've tried to re-adjust coil nulling: I've made a 7 turns-5cm loop and connected in series with rx coil.
Then moving it I' ve verified that I'm able to change phase shift and tension, but noticed that the minimum voltage doesn't correspond to the correct phase shift.
I've found a position where I get 4us delay in the rx signal respect to tx which should be 20 degrees (70/360*20)=3.8 but neither in this position nor in any other, I'm able to get a full good working. I mean I have always not a single but a double or even triple sound if target is swept slow and near the coil, and big iron is not completely rejected in discrimination mode.
Noticed also that ground connection of Rx coil shifts a bit the phase:
increments if connected to purple wire and decrements if connected to grey wire.
Detection depth is bad as before too.

So:
Is the method I used with the coil correct to fix the phase and offset of possibly not good original coil?

Is it correct a time difference of 4us for a DD coil (measured at output of pre-amp) for a required phase diff of 20°?

Which side of Rx coil should I connect to ground?

Should a DD coil give just a single tone for each target sweep or is it normal have a double tone?

4us is ok for the initial phase-shift at the RX pre-amp output. This does not correspond to a complete voltage null.

If you move a coin very close to the coil then a double-blip can be expected. Also, you cannot completely reject large iron with this design, but that does not present a problem in the field.

The purple wire should connected to the screen.

Perhaps you have a problem further along between the synchronous demodulator outputs and the audio input.