TESORO GOLDEN SABRE

[Max]

Hi Nelson,
about Gold Bug... if I remember well it's a 19KHz machine... but you have Gold Bug II so frequency must be much great ... 71KHz I read on a pair of websites.

The extremely hi-sens to thin objects is related to the higher frequency: you get more skin effects due to that frequency and so it can find even the smallest nuggets.

Drawback is that if there is a small piece of foil you'll get a very large signal from it also at medium depth.

That kind of detectors are extremely good for gold nuggets... and I saw also that weight is about 1.3Kg, that's really good and comfortable for long run.

If you mount a 12v 1.2Ah on the box you'll increase weight of 400-450gr thus giving you 1.7-1.75Kg that's a bit heavy... so I suggest you mount regulator in the battery case inside the control box... and keep the battery hip-mounted and connected with an extensible wire... like in table phones...by a connector to the control box. That way you'll save weight from arm and shoulder and get a relative freedom of movements too.

Kind regards,
Max

[Max]

"Oooh! I forgot to mention one imoprtant thing;..."

Oooh! I forgot to mention MOST IMPORTANT NEWS;
NO MORE OCASSIONALL CHATTERS AND BLEEPS on coil balanced this way...
He,he,he...!

Hi Ivconic,
my last reading on potted coil is about 5.5mVpp that is a bit more than I have when nulled first time. I think that little forces developed due to the epoxy reactions and hardening give me that deviation respect unpotted coil.

I read that with dummy load (1Kohm+15nF) and scope.

One thing to consider is that heat generation due to epoxy... the peak of temperature easy melt or make less heavy fixed the temporary fixings of TX and RX wounds on the housing... BTW my actual housing for this DD255x137 is not the best ...made of PVC plastic that you know is really sensitive to heat and can deformate due to its action.

Anyway, my very slow epoxy (the one for surfboards) revealed a maximum peak of 68 °C (70° C on specs) I've measured before sealing coil... so heat didn't damaged too much my coil null.

Coil sealed have now same performance as it unsealed... and I'm happy of that. Just I have to wait too much for epoxy end-reactions if have to make others. I've also made another DD22 same way.

About multimeters... and nulling, when you null without capacitor I guess you don't get a perfect sinus on RX leads but a disturbed signal (due maybe to e.g. 50Hz intermodulation and similar)...

If signal is not perfectly a sinus you'll get 0.000V on a digital multimeter very easy... cause they offer good readings only with sinus shaped signals... that's so cause of their internal ADC and circuit configuration... and also at higher frequencies you get still good readings if you have a perfect sinus signal but not on an arbitrary shaped one.

So I think that when you read 0.000v there's actually some magnitude but that your multimeter can't read properly , giving you zero on display.

Adding al foil pieces is like correcting overshots in PI coils with brass washer or similar... actually I think you'll underbalance coil that way... but you know that sometimes you'll gain better sens with a bit out-null config... expecially for non-ferrous items... also your phase shift will somehow balance ground phase shift in medium soils... that way you can use a back GEB setting and maybe detect e.g. silver coin at some depth more.

If you use thin ferrous foil or similar I think you'll need a far GEB setting cause of the added phase shift due to ferromagnetic materials.

Best regards,
Max

[Max]

Dear Max

We are fixing 1 k and 15N f to rx for nulling.
are we have to cut or solder 1 K AND 15 n to RX after Nulling.?

Regards
Erol

Hi Erol,
you need that components just to find null position and reading so the lowest voltage across them. After you fixed coils in that optimal position you'll disconnect rx leads from dummy load (resistor+capacitor) and connect to the PCB pads for RX as in schematic.

Another way to get similar result is connecting rx leads directly to PCB pads and nulling reading the lowest voltage at output of preamp. ic. : that way you don't need the external dummy load to null.

One way or another is your choice... both work for our purposes. I use dummy load cause I wanna read directly the voltage accross RX leads and (passive) load and compare with other readings I've made for other coils in the same way with same components, thus avoiding effects due to active device at preamp (in TGS is LF353) e.g. offset etc

Best regards,
Max

[nelson]

Ok Max and thanks for information about TGSL push switch.

About Gold Bug. Thats ok, you are 100 % correct and i will try the voltage regulator.

Today i whent to a river side, to see how this gold bug is performing.
Grund balancing is very easy to do, all functions are very useful for what the detector is done. If you try to do some coing shooting with it, can by good, but not so good has TGS. Discriminatin is fix to avoid only ferrous metals. TGS can discriminate on a wide range of metals conductivity. So my gold bug, will be used only for gold. Also i noticed how good this machine is on getting some very tiny metals. For example i made an experiment checking a detection of a small needle head. This was detected underground at about 3 to 5 cms.
Ok Max thanks again.

Best regards

Nelson


[quote=Max;60505]

Hi Max.
Yestarday i began to build TGSL and i noticed a push buttom on schematics, do you know what is this for?
About my post about Fisher Gold Bug 2, i ll made the voltage regulator, but i will like to know from you, if the detector runs only from 9 volts or 18 volts.
For me, i understand that the machine works with 9 volts.
i hope you can understand what i mean.
Best regards.
Nelson




Hi Nelson,
I think you're referring to the switch that is at comparator near diode D12 is for inserting or not the 1Mohm resistor parallel to D12.

This will give you an audio boost... but if you read Ivconic's post about stability you'll notice there is a drawback in having that 1Mohm resistor there... cause of more instability at max sens.

So using the switch you can enable or disable the audio-boost, depending if your current setup (pot positions etc) can tolerate a bit more instability or not.

You can also avoid 1M and switch if you feel comfortable just with original audio. Is your choice.

About Gold Bug the voltage is 9V cause the 2 batteries feed the circuit by two diodes... so battery+diode are parallel one each other... they did that way cause circuit maybe require more current respect to that a single 9V can provide for enough searchtime. That way each battery provide about 1/2 current ...so last twice.

You have to check if your circuit is the same as in schematic I provided and then build a 9V regulator if so.

BTW the real voltage is under 9V depending on drop on diodes... it's something 8.3 to 8.5volts... but you can safely use 9V regulator for circuit.

Best regards,
Max

[ivconic]

"Oooh! I forgot to mention one imoprtant thing;..."

Oooh! I forgot to mention MOST IMPORTANT NEWS;
NO MORE OCASSIONALL CHATTERS AND BLEEPS on coil balanced this way...
He,he,he...!

[ivconic]

Oooh! I forgot to mention one imoprtant thing;
So i gained 0.000mV on coil with 15nF attached....
Well, just for any case, i later removed capacitor and measured again. Still 0.000mV on RX!!! Very good! Remained zero balanced!!! PERFECT!
Conclusion: capacitor only helped me to very fine readjust balance. No fakes at all from it.
One more thing;
Max suggested 1k resistor to be added when nulling....well, i must say that resistor absolutelly "sucked" any mV over zero...So it is faking - omit it!
Make double test; null coil with resistor and than remove it and measure induction....You will be amazed! Later remove even 15nF just to check are there any fakes or not..
Those 5K1 on LF353 inputs are more than sufficient there. I suggest to experiment with various values, starting from 3k3 and up..But this mostly dependes on op-amp used at front end..
Bye!

[ivconic]

P.S.
You should appreciate this! I gave up one of "master secret" here!


When "secret" reach the public; it only means - new one is "cooking"...
Heh,heh,heh...
Very best regards!

[ivconic]

About nulling - balancing coils;

So far i made a lot of coils...Also experimented a lot...
Max can you repeat me your final measurements when your coil is nulled?
First is good to know that aint no multimeter with which we can accuratelly measure induced voltage on RX coil. Yes we can have some approx. results but not quite accurate...Why? Most of multimeters have good response on low frequencies, but on higher not! Error level rises up as frequency rising.
That's why oscilloscope is unreplaceable in accurate measurements..
But....in case we dont have osci.- must use what we have..Simply as that.
I do have quite useable multimeter with 200mV range AC/DC...So when finishing nullling coil i usually gain 0.000 mV...On first glance this sounds like a perfect balanced coil! But, as we know from experience...it is almost imposiblle to absolute balnce coils, due many objective reasons.
Above mentioned nulling is measured without 15nF parallel to RX coil. When i add that capacitor, induced voltage rises up to 0.009mv in most of cases. In few cases it raised up to 0.012mV...Than i triead again to fine readjust null to obtain absolute zero...yet without succes...Quite expectable.
But, somethimes i am to lunatic about those things...i want to push more and more, so today i made experiment with one coil. I nulled it with attached capacitor 15nF parallel to RX. Final voltage was 0.008mV...
I figured way how to achieve absolute zero; i put (carefully chosen) few very small pieces of Al foil inside coil housing, covering few spots on coils.Must mention those pieces are not connected anyhow in coil setup. Those pieces actually play role of "foreign body" inside coil. By moving them slowly,carefully inside coil i found exact spots and gained absolute zero balnced coils!!!
Actaully those Al pieces provoked minor induction, enough just to balance coil to zero.Coil is finished., filled with mass.Drained...and now is ready for terrain work. I checked it with detector.....PERFECT!!!! I gained extra 2cm's on single coin!!! Stabillity is good as it was before. Discrimination also good...
What to say? Crazy experiment gave me crazy result!!
Now i am thinking other thing; so i put Al pieces - "coloured" metal...What should be if i put iron pieces ("non-coloured") instead Al???
Only way to find out is to make another coil and try. I am planing to do that tomorrow...
I do know what is all about....perfectly clear to me. But i would like to hear your opinions...?
Heh,heh,heh...!

P.S.
You should appreciate this! I gave up one of "master secret" here!

[ivconic]

Generally you lose a lot of things at e-bay .

But my friend i can't help you. We are very small in order to resolve such issues
Anyway my regards
Btw... i want to make a OOcoil 20+20cm. Who is your opinion????

It will be deep! And i mean very deep! But as Max noted;y you should take special measures dealing with Faraday cage there..Must make hi-quality f.c....Personally i'' avoid Al foil in larger coils. I'll try some conductive material to obrain like graphite or simillar..There is certain skin effect occured when Al foil is used.Huge drawback! So, Al foil is suitable only for smaller diamm.coils...Another thing; less space between wires and foil - better. I am not usin any more scotch tape in between. When coil is wounded, next thing is to wind Al foil over it without anything in between.
20cm OO...good to try! If 0.25mm is used than you should start with 90 turns and measuring inductance try to adjust number of turns to achieve 6mH for TX ans 6.5mH for Rx...If 0.3mm is used than start with 120 turns...Do not pay to much of attention on resistances...If they are in range 17-25ohms than it will do the job. But do pay attention on inductances!
Bets regards!

[erolunall]

Dear Max

We are fixing 1 k and 15N f to rx for nulling.
are we have to cut or solder 1 K AND 15 n to RX after Nulling.?

Regards
Erol

[fish1985]

thank you for every thing .

[Max]

thank you for giving me the information. I will make coil at the nearest time and i'll notice the result from here. as a last question, which range is the best working frequence of TGS at?
thank you again.

Hi,
TGS have a spec frequency of 14KHz. Other models by Tesoro with motion-disc fall in the range 10KHz to 12.5KHz.

Some of newer have 17KHz or more.

I've found that my original 9x8 coil fitted on TGS give me a frequency of 14.35KHz.

In DD255x137 I get about 14.69Khz and unit performs really good.

I think that lowering frequency to 10KHz or setting up to 18-19Khz is possible but expecially for higher frequency you'll get problems related to more skin effects cause e.g. foil and coupling between stages.

So,if you made coils for it I suggest you set params to get anything from 14 to 15KHz... and it will run fine.

Kind regards,
Max

[fish1985]

thank you for giving me the information. I will make coil at the nearest time and i'll notice the result from here. as a last question, which range is the best working frequence of TGS at?
thank you again.

[Max]

hi,
I want to make O-O coil. I coudn't read the forum to the end from the start because my english isn't well enough. I will be grateful if you gave me the best O-O coil information.
thank you..

Hi,
they are nothing special at the end. You need matching the inductance and resistance for your TX side... then make a similar coil for RX... few more turns or same number (same to get full resonance, if you wanna try fully-resonant design).

All the rest is the same as other config, I mean nulling , shielding, potting etc

The big problem in making VLF coils is (as always, expecially for beginners) nulling it well, that means few voltage as you can get with a parallel load of resistor (e.g. 1Kohm) and a suitable capacitor (e.g. 15nF for goldensabre) to get about resonant frequency of LC tank near to TX frequency (fundamental freq. nulling).

So... first you need to know TX coil specs... then you have to calculate turns-wire for getting right values... then make TX coil with say 10% more turns than calculated... then try to reduce turns to get right operative frequency.

After that you'll made RX coil... and then you'll null.

I do before shielding always air-tests to see if it works or not... but if you do so then you have to null again after shielding (so null 2 times).

At the end is more easy than making e.g. DD coils... but problems are related to housing/potting, GEB/false signals for great diameters and also sweeping the coil on ground in the right way (without tilting).

Kind regards,
Max

[fish1985]

hi,
I want to make O-O coil. I coudn't read the forum to the end from the start because my english isn't well enough. I will be grateful if you gave me the best O-O coil information.
thank you..