TGSL Tuning & troubleshooting

[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]

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.

[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....

[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]

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...

[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.

[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.

[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...

[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.

[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

[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.

[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]

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?

[Qiaozhi]

If you read most people's posts, after constructing a TGSL or similar design, they usually end up with around 20cm detection distance for a 1 euro coin when using an 8" coil. In general, the detection distance for a 1 euro coin is approximately equal to the coil diameter.

However, by using different coil inductances, so that the TX and RX frequencies are closer together, the sensitivity can be increased. But there are a number of problems with doing this. Firstly, it becomes more difficult to balance the coils. Secondly, you may not be able to achieve the correct initial phase-shift. Thirdly, the residual RX amplitude could overload the RX pre-amp.

It's a fine balancing act. That's why the manufacturers (such as Tesoro) go for a more conservative approach to make the coils easier to manufacture.

The bottom line is that there is unlikely to be anything wrong with the electronics. Try testing the circuit with a commercial coil to see what I mean.

[ivconic]

If you read most people's posts, after constructing a TGSL or similar design, they usually end up with around 20cm detection distance for a 1 euro coin when using an 8" coil. In general, the detection distance for a 1 euro coin is approximately equal to the coil diameter.

However, by using different coil inductances, so that the TX and RX frequencies are closer together, the sensitivity can be increased. But there are a number of problems with doing this. Firstly, it becomes more difficult to balance the coils. Secondly, you may not be able to achieve the correct initial phase-shift. Thirdly, the residual RX amplitude could overload the RX pre-amp.

It's a fine balancing act. That's why the manufacturers (such as Tesoro) go for a more conservative approach to make the coils easier to manufacture.

The bottom line is that there is unlikely to be anything wrong with the electronics. Try testing the circuit with a commercial coil to see what I mean.

Exactly.
Proper coil nulling is not an easy job. I think most people understood nulling as just simple task. Pitty, it is not like that.
At some coils i spend 5-6 hours to null them properly. Amateur conditions do not offering me comfort, so nulling is time&nerves consuming tough task.
Than again...at some coils i achieve good balance in just 20 minutes.
It is all about quality made and details.
Usually i am using hot melted plastic glue gun and put "punkts" (points) over the coil to attach it to holder good. Than i must wait hot glue to dry and get cold. Than again to correct balance by slitest (parts on millimeter) movements of some coil segments. Than again to wait to see influence of temperature changes in workshop....and again..and again. All the time RX coil is attached to millivoltmeter and observed. TX coil is attached to TGSL TX out.
Sometimes process is going pretty smooth and everything ends in 20 minutes....but sometimes it took time to be done. It can took hours sometimes.
Once coils are balanced well i use joint filler (2 components epoxy) to finish coils. It all must be done in one move, fast, not to allow temperature changes to affect balance. If you balance coils and let them overnight....those will move for sure and spoil the balance much.
Tough job to make good coil in amateur conditions. Not easy.


....

That's why i am thinking to give up of making DIY coils finally, lately. It is more cheaper to buy original coil and adapt detector to work good with it.