TESORO GOLDEN SABRE

[ivconic]

Does the signal return to a good clean sine wave when you bring a coin towards the search head?

No it stay the same/you mean LF353pin1!/.What makes you think that I over-nulied the coils?I think that there is too much surrounding noise and I miss the null.In same time how chain is affected and show less sensitivity.
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Check C9 (100pF) and replace it with some high quality cap.

Have just check it again.Its 100p.Change with some scraped from old Tv/which looks ok/.No change.
10p again on its place.

Try 50pf (56pf or 68pf) than and scope it... Although i think Qiaozhi is right...

[Pompey]

When disrimination pot is replaced with 10k sinus on pin1 improves.Sinus on pin1 depends from Tx sinusoide.I tried this.When you put 10k disc pot Tx signal goes weaker and it`s crack at the top disapears -sinus on pin (LF353) improves too.I think that disc. pot must be 10k -in TGS there are 100k and 10k paralel,so 10k is correct I think.

[simonbaker]

Hello,
So there is possibility that everything on pcb is ok and still device can't reach good depths?And this is with good coil?
So I will just make another one and see if there are differences.I test every new coil also with two other TGSLs/BD140/and one TGS.
Yesterday I try to null last coil better and I get down to 0.004/200mV.And today switch on the setup as I leave it and read .940/2V.Its not the multimeter.Must be noise from TVs,security radios,cells,etc.
When I tune it were late.And maybe less of those.
I wont quit on this also.

The best that I reached is with BD140 version.With 22cm coil/22cm in air for 1e coin.
Now I remember that you use 4K7 for R13 and R14.I have mount 5K1.I will try now to see is there any change.

SB glad that you are back on this too.
now, cannot participate.
Why?

Unfortunately health problems of wife takes all time for now. But I have not lost desire to get to bottom of intriguing mysteries of TGSL -- especially because my TGSL performed similar to Ultimate_Haze -- but will have to wait for the future now.

Good luck, you may find answers first!

-SB

[Ultimate_Haze]

Hi,
Simonbaker.
Sorry to hear this.Wish fast recovery.

[Ultimate_Haze]

I just got new multimeter.Its VC9805A.Think that its previous version of the one you show.Because dont have backlight.
So it shows quiet different readings.Frequency is with some old coil is 15,2 and old one shows 14,2.Also my LC meter is wrong too.It shows 6,35mH on one winding and this new multimeter shows 6,75mH.
It must be that my units are damaged somehow.
I will make new coil using this VC9805A.Hope that this will solve my problems.

[ivconic]

I just got new multimeter.Its VC9805A.Think that its previous version of the one you show.Because dont have backlight.
So it shows quiet different readings.Frequency is with some old coil is 15,2 and old one shows 14,2.Also my LC meter is wrong too.It shows 6,35mH on one winding and this new multimeter shows 6,75mH.
It must be that my units are damaged somehow.
I will make new coil using this VC9805A.Hope that this will solve my problems.

That explains everything...
Now you know why i keep 5kg hammer near me, all the time!

[WM6]

.Also my LC meter is wrong too.It shows 6,35mH on one winding and this new multimeter shows 6,75mH.

Not necessarily wrong.

Measurement result depends on the measuring frequency of L-meters.

Closer than this frequency is to the operating frequency of MD, more correct are results.

[Ultimate_Haze]

I will take this advice.5kg.hammer will do the job just fine!Bang.
So this must be the reason why I cant null those coils.They just refuse to go lower then .200/2V AC.
Today I will make some new coils and inform you here about the results.Pity that I almost destroy this nice pcb.Solder and desolder all the time various components.And it were wrong L all the time.
Regards.

[ivconic]

I will take this advice.5kg.hammer will do the job just fine!Bang.
So this must be the reason why I cant null those coils.They just refuse to go lower then .200/2V AC.
Today I will make some new coils and inform you here about the results.Pity that I almost destroy this nice pcb.Solder and desolder all the time various components.And it were wrong L all the time.
Regards.

Not only that but all the time you've been kept on your mind wrong values. Horrible situatuion. I should know that very good cose i "wandered in a fog" for sometime. Until hammer did pretty nice job! Now with new multimeter things simply came on their places.
All the calculations with old values are now pointless.

[Lambada]

Hi, sorry for my interruption, but I have a question. Does TSGL has a X/Y Chanel to attach a VDI godograph? Like http://md4u.ru/img_godo/th_godo_v204_001_l.jpg

If not, which one of tesoro's can be attached VDI meter?

[Ultimate_Haze]

Have finish one new coilTX6.03mH;RX6.28mH.Some minor change.Now will try to make 6,50 for RX.
And still the coil refuse to null lower then .180/2V AC.
The thing that bugs me is that I read 15,9kHz form 2n2907 and 14,7kHz from 4024 pin1.Some changes in lf353 pin1 too but still not even similar to sinus.
Will continue to examine and will post some pictures later.

[simonbaker]

Hi,
Simonbaker.
Sorry to hear this.Wish fast recovery.

Thanks U_H.

Regarding LC meter: who knows which one is more accurate? I did a test:

http://www.geotech1.com/forums/showthread.php?t=15668

We can only be approximate I think when it comes to LC measurements.

But why so important? As some other have pointed out, it should be possible to adjust capacitors slightly if coil is not exact, if clearly understand relationships. If not, that is a mystery in itself.

Look, metal detectors operate at many frequencies. It should be possible to make a TGSL that runs at other frequencies than 14.5 kHz. If not, why not? Tesoro does not always choose 14.5 kHz for their detectors, many of which have very similar circuitry.

I wish I had smart answer. For now, keep building and trying. The answer is there somewhere.

-SB

[ivconic]

Thanks U_H.

Regarding LC meter: who knows which one is more accurate? I did a test:

http://www.geotech1.com/forums/showthread.php?t=15668

We can only be approximate I think when it comes to LC measurements.

But why so important? As some other have pointed out, it should be possible to adjust capacitors slightly if coil is not exact, if clearly understand relationships. If not, that is a mystery in itself.

Look, metal detectors operate at many frequencies. It should be possible to make a TGSL that runs at other frequencies than 14.5 kHz. If not, why not? Tesoro does not always choose 14.5 kHz for their detectors, many of which have very similar circuitry.

I wish I had smart answer. For now, keep building and trying. The answer is there somewhere.

-SB

Agree.

[Dennis the Mennis]

Coil values not right ...

I only got low distances with not so good nulled coil so far. Doubt in coil remains in your case too.
What about ferrite? Take 10cm long ferrite rod and check if it is fully rejected up to 5cm away from coil surface.. Than check with some small and thin silver coin is it accepted at the same adjustments when ferrite rod is rejected... Inform us here.
Cheers

I'm not going to say, "told you so".

Looking at the values for your coils and the tuning caps used, I have calculated your TX frequency to be 14.5KHz, which you have confirmed is correct. However, your RX circuit is tuned to 19.7KHz, which in my opinion is too high, as Tesoro circuits are usually off resonance by around 9%. In this case you should be using a calculated capacitor value of 15.5nF to tune the RX to 15.8KHz. I would suggest trying a 15nF cap instead of the 10nF and see if there is any improvement.

I wrote " 15n // 4n7 for Tx " but it had to be 22n // 4n7
> when I calculate this with the frequency 14.5 KHz I get 4.51mH for the TX coil ....

I should have been more suspicious when I removed all the dust and spider webs from that MultiMeter .

Anyway the values given by the MultiMeter are way too high .
This explains hopefully a lot .
Here another hint pointing in the same direction ...

Another thing;
am i wrong or i see TX amplitude there barely over 10vpp ( I get aprox 12v )?
That could be the cause of poor depths.
Usually amplitude is 15-16vpp at TGS/TGSL...

And here Ultimate_Haze with apperently same problem .... brother in disaster

I just got new multimeter.Its VC9805A.Think that its previous version of the one you show.Because dont have backlight.
So it shows quiet different readings.Frequency is with some old coil is 15,2 and old one shows 14,2.Also my LC meter is wrong too.It shows 6,35mH on one winding and this new multimeter shows 6,75mH.
It must be that my units are damaged somehow.
I will make new coil using this VC9805A.Hope that this will solve my problems.

I went to electronicshop and measured the coils there with LC meter the values to be sure ... much lower values
I try to calibrate the inductance part of the meter and to make sure everything is correct I will measure the inductance with frequency generator and cap again for oscillationfrequency .

I'll be back ...

regards

Dennis the Mennis

[Math]

hi Ivconic ive had a look &think TGSL is a great project &am going to try to build one as my first project~ i've had alook at the complete details in the projects section and just wanted to check on a couple of things before i start~

-for the capacitors they all match up with the parts list and schematic but when i looked at the placement OC theres seems to be ten 0.1 on there &only one on the schematic&parts list, also five 0.022 instead of seven on the schematic and for the RXc shown on the placement, is this just the one 0.015?

-for the resistors i havent checked with the placement OC yet but on the parts list~ R1 2k2 & R2 24K & R52 330are missing, also R4 1K & R5 330 ithink must be R56 &R55, there are 3 values for R6 im checking the first one 47K is right~ and for the amended R13 &14 values the schematic shows 4K7 but parts list has 5K1 could you let me know which to use, thanks~