TESORO GOLDEN SABRE

[Max]

damn slow epoxy

my new epoxy seems a bit slow... it takes 2 days to harden well... and maybe 6-7 to get reactions end !

I've found a dealer that sell 1Kg at 9eur of that thing... it's clear and transparent ...used for making snow and surfboards and things like that... but man... it's slow slow slow !

Price is ok... but have to wait and it's boring...

I'm start feeling like Bear in the Big Wednesday !

What's your epoxy choice or preferences ???

Do you use different stuff... !?

Please expose here your epoxy/fixing stuff!

Kind regards,
Max

[Max]

noise considerations from notch section ic

Hi,
these are the numbers for input noise (@1KHz):

TL062 ----> 42nV/sqrt(Hz)
LF442 ----> 35nV/sqrt(Hz)
TLC2262 -> 12nV/sqrt(Hz)

So LF442 is better than tl062 but can't beat TLC2262 on that... I suggest you use tlc2262 if you find it... not so easy sometimes... somewhere... or a better dual op. amp.

Kind regards,
Max

[Max]

>>>>>>If notch section is present other bleeping is related to the bad choice of TL062 that's a very old and noisy IC: I have changed with TLC2262 from TI... and fixed that.


Hi Max!
What's about LF442N instead of TL062?

Regards
Darko

Hi,
yes it's in the original schematic. I've not tested it ... but for sure is better than TL062 there.

Best regards,
Max

[Darko]

>>>>>>If notch section is present other bleeping is related to the bad choice of TL062 that's a very old and noisy IC: I have changed with TLC2262 from TI... and fixed that.


Hi Max!
What's about LF442N instead of TL062?

Regards
Darko

[Max]

suspicious fake LM308s

Hi all,
here are some pictures of them:

1 is upside of one of them look at the "N" (National)

2 is downside of it look at the number or "g"

3 is downside of both... then first difference the second have no number/g but seems have an epoxy melt in bad way ... but on the top they are labeled the same... even the timemark/fab is the same : it's M12AH and maybe mean they are from 1912 !

4 is original national lm308 look again at the National symbol (this time original) and compare with first picture: they are different.

5 is original one meta-can type

What do you think now ?

For me are fake LM308... also materials are bad quality... you can break leads just with a little pressure... but in original ones you can move pins without damaging at all.

Epoxy melt is not in standard of quality for National devices... I have many and not a single one is in these conditions.

Better to keep eyes well open before buy... these are S..T devices... maybe some LM748 relabeled.

Best regards,
Max

[Max]

Hello All

http://xoomer.alice.it/sillanumsoft/index.htm

Pc software for Osciloscope

İvconic I thing You can design İvconic deep scan heavy

how can use with PC for detection?

Regards
Erol Ünal

Hi Erol,
using a PC e.g. laptop for MD is possible but often not good in results as one can think. You can use e.g. an Sample-and-hold ic and AD converter (or just AD with integrated S/H) to convert an analog value and read it by a PC port then elaborate by some program etc
Robert Hoolko's project was similar to that... using an MCU to do calculations and having a PC interface for a VLF digital machine.
Much more easy is do same thing for the Pulse Induction type of detectors.
In both cases you need a very fast hardware for ADC and for calculations between sampling.
At the end the process is good and you can avoid almost all op. amps needed in conventional analog designs... and gain same performance of top of the range analog detectors but you'll not gain more depth that way cause you cannot increase SNR that way over and better than analog designs in practice... at least I saw that till now. Much is related to preamp. cabability and coils to give you readings in reliable way (ultra low noise) and for very small signals (under 1uV range).

Best regards,
Max

[erolunall]

free Oscilloscope pc software

Hello All

http://xoomer.alice.it/sillanumsoft/index.htm

Pc software for Osciloscope

İvconic I thing You can design İvconic deep scan heavy

how can use with PC for detection?

Regards
Erol Ünal

[erolunall]

free Oscilloscope pc software

Hello All

http://xoomer.alice.it/sillanumsoft/index.htm

I find this link for PC . can we use for PC lap top Tesero deep model?
or Delta pulse PC model , İvconic, Max and other friends

Best Wishes
Erol

[Max]

the big problem with obsolete parts...

Are you certain that the comparators are not going into oscillation? This would cause the exact symptoms you are experiencing.

Hi,
yes of course... output comparators are always on the point of saturate when bad things are in the circuit (like the TL062 of notch... very bad idea having one there).

But that could not be the problem.

I noticed that 2 spare LM308N I bought last week have strange markings... so seem fake-op-amps.

They have a N like the National logo ...but different from it...on the left but I start thinking they are fake devices from asia... probably some LM741 with erased markings and then relabeled as LM308N!

I say that cause I had the metal-can ones and other parts and all seems ok with them but when I put those suspicious parts I get the device singing the macarena.

I have to post pictures of them... but can't take at the moment.

I trust people at shop who sold me that stuff and so think that the distributor they buy from was fraud by some singapore or something "dealer".

I was lucky cause bought just two... and don't need to complain with shop... for 1.80 eur expense... nevermind.

I've just signaled to the guys there and they are surprised of that. They bought something 40 of them cause there is request for DIY audio and RATs etc but now... with my little help... and few words of advertising I think they would throw all the stuff in the WC... and complain with distributor!

The story seems too strange ? Uhm... look at those pictures here:

http://sound.westhost.com/fake/counterfeit-p2.htm

So guys keep the eyes well open before buy many of these LM308N pearls.

Kind regards,
Max

[Qiaozhi]

Hi
Anyone have an idea of the influence of gap position in the shield to the performance of the coil? i mean , where is the best place for the wires to com out from the coil, so the interaction is minimal ?
Maybe this make no diference,but...
Fred.

I do not think the gap position will have any noticeable effect on the performance of the coil. It's just important that there is a gap.

Hi
Anyone have an idea of the influence of gap position in the shield to the performance of the coil? i mean , where is the best place for the wires to com out from the coil, so the interaction is minimal ?
Maybe this make no diference,but...
Fred.

[Qiaozhi]

Are you certain that the comparators are not going into oscillation? This would cause the exact symptoms you are experiencing.

[Max]

"Problem is solved!..."
Well....not complete! I took last finished TGSL on the field with me yesterday.
Yes it is good and deep. I found 254 small roman coins, working 5-6 hours there!!!
It is top record for me! So far!
This device is without 1M resistor.No more loud and often bleeping but still there
are ocassional short decayed "tic-tic"!?
I obey what Max suggested and tried to more precise adjust GND trimmer there - on the
real field, under real conditions. But...!? Still if i pull up and lower down coil fast
to the ground, device is producing some false signals...? I tried several times, no way
to adjust it not to produce false signals at all!? In my workshop it is not reacting on
pure ferrite bar at all...Absolute calm, no false signals at all.
This returns me again to suspect on coil!? Horror! Coils are nulled on already described
way. Measuring with very good multimeter while nulling. At the end coils are nulled to
point where i have 0.000-0.001v AC on RX ends... I simply connect meter with RX coil ends
without adding capacitor and resistor Max talked about. Could this be a mistake?
I have some old,obsolete scope...When testing with it i just cant null coil fine due small
resolution of scope itself.
This latest behavior is not disturbing much for user. Bleeps are rare and ocassional.Also
audio volume when bleeps is very low, so it is very easy to distinguish among right detection
and false signal.But.....i am not satisfied with this...i want to find out what is problem
and to better understand this.
There is a way to stop this - lower Sensitivity to 50% pot scale...After that, device is very
calm. Only produce again very short decayed bleep if coil hit some rock or bulky grass arround.
Even than it is at very low audio level..very silent...
First thought was; it must be arround coil...? But i am not sure.
Second idea occured me is; could it be due Al foil cage over coil? Maybe all this came from
Al foil? I have no condition to make Faraday cage from other,better material ..so far.So i
used self adhesive Al foil tape..

Hi Ivconic,
I think problem could be in the circuit and not coils... of course I never used one of your coils but we use about same materials and I've made a coil for TGS like yours (255x137) following your specs. And I think yours are great/good coils.

Also I have original tesoro coil 9x8 I bought and behaviour is the same with same components on PCB, so at least for me, bleeping is not related to coils.

What I noticed is:

LM308N, that's very good about depth on this design, actually introduce some more bleeping than TL081. Less with LM308AH version but you know is very expensive and hard to find.
That's a big drawback... you gain depth cause of different input stage etc but you lose also cause of erratic bleeping, cause have to keep sens pot at lower setting.
Think that solution to this problem is finding some good op. amp. with bipolar inputs and with much better noise figure than 308... but it's really hard and I have no idea at the moment.

If notch section is present other bleeping is related to the bad choice of TL062 that's a very old and noisy IC: I have changed with TLC2262 from TI... and fixed that.

The fets introduce noise spikes in the signal path cause of their commutation. Using BF245 problem is not enormous but one can see very well on scope. I think that's not a big issue cause that noise is syncronous... but other sources (like 308s) give random spikes.

Also if coils are out null for more than 4-5mVpp I noticed and increase in noise with same components... otherwise not.

Circuit need extreme cleaning (like many other MD boards) cause of the hi amplification.

If you have near a noise source like electric interferences, fluorescent-lamps etc TGS with also original coil could give lot of false signals... even if coils are perfectly shielded.

I think that if you have to keep sens at 50% to avoid bleeping you probably have some "bad" component on your boards: I mean for "bad" a too noisy one.

I suggest you check the LM308s and LM358 for on-board noise you'll ear on the field.

About GEB and total null ...well, it works, but in middle soils much better than others with too iron oxides.

Best regards,
Max

[Qiaozhi]

"Problem is solved!..."
Well....not complete! I took last finished TGSL on the field with me yesterday.
Yes it is good and deep. I found 254 small roman coins, working 5-6 hours there!!!
It is top record for me! So far!
This device is without 1M resistor.No more loud and often bleeping but still there
are ocassional short decayed "tic-tic"!?
I obey what Max suggested and tried to more precise adjust GND trimmer there - on the
real field, under real conditions. But...!? Still if i pull up and lower down coil fast
to the ground, device is producing some false signals...? I tried several times, no way
to adjust it not to produce false signals at all!? In my workshop it is not reacting on
pure ferrite bar at all...Absolute calm, no false signals at all.
This returns me again to suspect on coil!? Horror! Coils are nulled on already described
way. Measuring with very good multimeter while nulling. At the end coils are nulled to
point where i have 0.000-0.001v AC on RX ends... I simply connect meter with RX coil ends
without adding capacitor and resistor Max talked about. Could this be a mistake?
I have some old,obsolete scope...When testing with it i just cant null coil fine due small
resolution of scope itself.
This latest behavior is not disturbing much for user. Bleeps are rare and ocassional.Also
audio volume when bleeps is very low, so it is very easy to distinguish among right detection
and false signal.But.....i am not satisfied with this...i want to find out what is problem
and to better understand this.
There is a way to stop this - lower Sensitivity to 50% pot scale...After that, device is very
calm. Only produce again very short decayed bleep if coil hit some rock or bulky grass arround.
Even than it is at very low audio level..very silent...
First thought was; it must be arround coil...? But i am not sure.
Second idea occured me is; could it be due Al foil cage over coil? Maybe all this came from
Al foil? I have no condition to make Faraday cage from other,better material ..so far.So i
used self adhesive Al foil tape..

Hi Ivconic,

There is an easy way to find out if the problem is in the detector or in the coil. Why not test your TGS using an original Tesoro coil?
Personally I would be suspicious of the shielding in the coil. You can also try using an electrostatic sheet in the base of the coil housing. Garrett do this in their Crossfire coils. The sheet is then connected to the coil screen via a large spring that presses on the sheet.

[ivconic]

!

"Problem is solved!..."
Well....not complete! I took last finished TGSL on the field with me yesterday.
Yes it is good and deep. I found 254 small roman coins, working 5-6 hours there!!!
It is top record for me! So far!
This device is without 1M resistor.No more loud and often bleeping but still there
are ocassional short decayed "tic-tic"!?
I obey what Max suggested and tried to more precise adjust GND trimmer there - on the
real field, under real conditions. But...!? Still if i pull up and lower down coil fast
to the ground, device is producing some false signals...? I tried several times, no way
to adjust it not to produce false signals at all!? In my workshop it is not reacting on
pure ferrite bar at all...Absolute calm, no false signals at all.
This returns me again to suspect on coil!? Horror! Coils are nulled on already described
way. Measuring with very good multimeter while nulling. At the end coils are nulled to
point where i have 0.000-0.001v AC on RX ends... I simply connect meter with RX coil ends
without adding capacitor and resistor Max talked about. Could this be a mistake?
I have some old,obsolete scope...When testing with it i just cant null coil fine due small
resolution of scope itself.
This latest behavior is not disturbing much for user. Bleeps are rare and ocassional.Also
audio volume when bleeps is very low, so it is very easy to distinguish among right detection
and false signal.But.....i am not satisfied with this...i want to find out what is problem
and to better understand this.
There is a way to stop this - lower Sensitivity to 50% pot scale...After that, device is very
calm. Only produce again very short decayed bleep if coil hit some rock or bulky grass arround.
Even than it is at very low audio level..very silent...
First thought was; it must be arround coil...? But i am not sure.
Second idea occured me is; could it be due Al foil cage over coil? Maybe all this came from
Al foil? I have no condition to make Faraday cage from other,better material ..so far.So i
used self adhesive Al foil tape..