TESORO GOLDEN SABRE

[Qiaozhi]

"...There's nothing more annoying than trying to trace a fault. and finding that you've fitted the wrong component. ..."

Ha,ha,ha,ha,ha!!! Story of my life!

Probably story of anyone building electronic stuff, but not everybody will admit it

I was speaking from experience.

[Fred]

"...There's nothing more annoying than trying to trace a fault. and finding that you've fitted the wrong component. ..."

Ha,ha,ha,ha,ha!!! Story of my life!

Probably story of anyone building electronic stuff, but not everybody will admit it

[ivconic]

"...There's nothing more annoying than trying to trace a fault. and finding that you've fitted the wrong component. ..."

Ha,ha,ha,ha,ha!!! Story of my life!

[Qiaozhi]

Dear Qiaozhi
actually i have osciloscope but i dont know how to find a fualt with it
i just borrowed from frind also its very old russian Model
everthing in russian whritting only have one channel?
Dear Sir is it possible to give me some example about how to
find a fault on TSGL with scop please..
because TX sometimes gives me very perfect sine wave but some times
abit changes let me explain...
i have wond 4 coils each with abit different value than original
that described by Ivconic but one of the exactly 6mh for TX and 6.5 for RX
i am not satisfied with one of the caus sometimes i get around over 20cm for single
1.7cm silver coin and sometimes no more than 15cm..
leave the coil nulling caus i am sure your saing the problem with coil nulling
so for example lets forget about discrimination just all metal ok
the deepest response from any coil at any RX voltages mean the machines most depth?
after you get best depth then you can adjust disc GB and everything else
i hope you understand me because English is not my language
very thanks

I think I understand what you're saying.

Firstly, the single-channel oscilloscope can be useful for simple fault finding, but for setting up the coil properly and to understand what is going on, you really need a two-channel.
Try following the instructions I gave you before:

There are 2 JFETs in the design, labeled J107. The lower one is located in the GEB channel, and you must measure at the source pin of this transistor. i.e. across C12 (0.22uF).
But ... first move the coils together until you get close to the null point, when measured at the output of the pre-amp U101a. Then continue increasing the overlap of the coils until the voltage at the source pin of TR5 reaches zero. You do not have to be really accurate with this, as you can adjust the GEB control to compensate.
Next, if you re-measure the voltage at the output of the pre-amp, it will not be zero. This is normal. Tesoro coils have a residual voltage of about 15mV, which results in around 600mV to 700mV at the pre-amp output.
If the discrimination rejects non-ferrous instead of ferrous, then flip over the RX coil connections and start again.

BUT ... use the oscilloscope to monitor the source pin of TR5 (or across C12). This will be a more accurate measurement.

[metaldetector107]

TGSL

Dear Qiaozhi
actually i have osciloscope but i dont know how to find a fualt with it
i just borrowed from frind also its very old russian Model
everthing in russian whritting only have one channel?
Dear Sir is it possible to give me some example about how to
find a fault on TSGL with scop please..
because TX sometimes gives me very perfect sine wave but some times
abit changes let me explain...
i have wond 4 coils each with abit different value than original
that described by Ivconic but one of the exactly 6mh for TX and 6.5 for RX
i am not satisfied with one of the caus sometimes i get around over 20cm for single
1.7cm silver coin and sometimes no more than 15cm..
leave the coil nulling caus i am sure your saing the problem with coil nulling
so for example lets forget about discrimination just all metal ok
the deepest response from any coil at any RX voltages mean the machines most depth?
after you get best depth then you can adjust disc GB and everything else
i hope you understand me because English is not my language
very thanks

[Qiaozhi]

Dear Max IVco Qiaozh

about capacitor and resistor tolarence i usually test for exact value before putting on PCB does tolarence is important?
does tolarence changes when the circuit is closed i mean any differences
in tolarence when the circuit is ON or OFF?
also isf possible the most important part of Last TGSL by Ivconic
this time i making a new machine so before assembling anything i wish all of you to tell my best advice

best regards

The TGSL design doesn't need exact values, and can operate very well using a wide tolerance.

However, you might want to measure each component (just for your own peace of mind) particularly, since I seem to remember, that you do not have an oscilloscope. There's nothing more annoying than trying to trace a fault. and finding that you've fitted the wrong component.

[Max]

Dear Max IVco Qiaozh

about capacitor and resistor tolarence i usually test for exact value before putting on PCB does tolarence is important?
does tolarence changes when the circuit is closed i mean any differences
in tolarence when the circuit is ON or OFF?
also isf possible the most important part of Last TGSL by Ivconic
this time i making a new machine so before assembling anything i wish all of you to tell my best advice

best regards

Hi,
the tolerance is intented just at room temperature (20 or 25°C) and in a fixed range of humidity. The tolerance is a factory parameter that tell you the actual value of e.g. a resistor (but same apply to other components) could be between (nominal_value-(tolerance*nominal_value)) and (nominal_value+(tolerance*nominal_value))...

so , with an example is more easy to see..., say you have a nominal 1000 ohm resistor with 5% tolerance... you can expect values in the range from 950 ohm to 1050 ohm.

In colors you'll get brown-black-red + gold (for 5% tol)

Then , the actual value caould be also 1000 ohm exactly like the nominal value but just like a case... there's a statistical distribution of actual values in the boundaries described... 5% less or more than nominal.

The actual value of component is measured when out of a circuit: if component is e.g. under current effects it could change slightly... that's normal.

For example, resistor have the joule effect ... the current will make heat and then that heat though dispersed by e.g. air sinking will alterate actual value of resistor... but depending on how it's made (technology employed) you could see that actual value decrease or rise... in e.g. wire wound resistors the metal wire become longer cause of heat and thus the apparent resistance is increased... in other kind could be the opposite.

That apply also to caps, inductors etc... a cap change value with e.g. temperature variations... same for inductors... etc

So, tolerance is an issue that's interesting just from a static point of view... but variations are due to e.g. environment thermal changes etc some devices are expecially sensitive to such events... like e.g. semiconductors that in e.g. bipolar transistors will show increased minority carries with temperature increase , so also e.g. diodes , expecially old germanium kind or shottky barriers even silicon made... etc etc

You must keep in mind that so... the actual value of a component is unknown nor even predictable without making a serious model of it and e.g. simulating in pspice that changes... but , usually, in md applications that are not critical factors unless some VERY extreme performace will require VERY stable components values... so a lot of care about compensating that effects is usually mandatory in that cases, but are very special cases.

In tgs it's never true; components could change value without much effects cause it's not extreme design, but anyway very perfomative for general purpose.

Kind regards,
Max

[metaldetector107]

Dear Max IVco Qiaozh

about capacitor and resistor tolarence i usually test for exact value before putting on PCB does tolarence is important?
does tolarence changes when the circuit is closed i mean any differences
in tolarence when the circuit is ON or OFF?
also isf possible the most important part of Last TGSL by Ivconic
this time i making a new machine so before assembling anything i wish all of you to tell my best advice

best regards

[Max]

hi all again
i asked Max about the shield inside TV coax cable to use instead of
kitchen alaminum foil becus it strong and easy to tighten it not like
alaminum foil which is so weak so u cant tighen it...
Max said TV cable shiel does effect on performance
IN % please caus i am tired with alaminum foil i dont like my coils cous of it?
any help
best regards

Hi,
there are too many kind of cable shielding materials... many kind of aluminium shields you could find, some are thick and heavy ... some others are light and not much heavy than kitchen foil stuff. Some are mylar stuff... plastic+aluminium with very thin aluminium layer.

So give a unique answer is impossible unless you provide more data about the shielding material you're using, e.g. a picture of it or a measure of thickness etc

The shield used in coaxial cables you can use for shielding vlf md coils but , depending on that factors of above, you could make an "heavy" or "light" or "intermediate" shield.

Let me explain... a conductor all around your coil will always act as faraday shield when you'll connect to a fixed potential (gnd) but then the "impact" on coil will be different... it's anyway always metal sheet that you wind alla around coils and that HAVE an effect.

You know that shielding coil, for example, will alter the inductance of coil and thus frequency you'll get at tx or at rx resonant tank, that's obvious consequence.

Now , the heavier the shield it is the more the side effect.

In VLF coils is not so relevant issue at the end... you'll drift frequency and lose a part of performance if too heavy but in e.g. PIs ...well better buying a ready made one if wanna use such stuff for real!

But remember the more the thickness the more the conductance also and the more you'll get eddy currents from shield that will swamp part of target's eddy currents...you could saturate preamp using thick enough shield ! So it's better stay light.

Just my 5 cents.

Kind regards,
Max

[metaldetector107]

TGSL

Dear Ivco Max Qiaozh

i asked Max about the shield inside TV coax cable to use instead of
kitchen alaminum foil becus it strong and easy to tighten it not like
alaminum foil which is so weak so u cant tighen it...
Max said TV cable shiel does effect on performance?
IN % please caus i am tired with alaminum foil i dont like my coils cous of it?
another thing capacitor and resistor tolarence i usually test for exact value before putting on PCB does tolarence is important?
does tolarence chamges when the circuit is closed i mean any different when the circuit is ON or OFF?
any help
best regards

[metaldetector107]

SHIELD

hi all again
i asked Max about the shield inside TV coax cable to use instead of
kitchen alaminum foil becus it strong and easy to tighten it not like
alaminum foil which is so weak so u cant tighen it...
Max said TV cable shiel does effect on performance
IN % please caus i am tired with alaminum foil i dont like my coils cous of it?
any help
best regards

[Qiaozhi]

Dear Sir
thanks for replying me
i have made a test of nulling coil as you described for me
but i couldnot get less than 4.7mv
i spent half a day before it was easy to null as Ivconic way only few seconds
but honsely i belive in your way in nulling but dont tell Ivconic he gets angry very soon
lets see what i done i put 100k GB resistor on mid position
and put a -lead on body and
+lead on pin7 of LF353 is it right??
please if you dont mind explain for me i know you reported many times
just this time again please by the way the result was around 10cm for silver coin 1.7cm ..
Dear Qia the 100k GB is around 96k i tried to get exact value but i could not cuz of resistor tolarance

thanks alot

OK - I see you've posted the same message here that you sent in your PM.

Therefore I'll also post my reply here, so that others can see the answer:

----------------------------------------------------------------------

No - you are measuring the signal in the wrong place. There are 2 JFETs in the design, labeled J107. The lower one is located in the GEB channel, and you must measure at the source pin of this transistor. i.e. across C12 (0.22uF).
But ... first move the coils together until you get close to the null point, when measured at the output of the pre-amp U101a. Then continue increasing the overlap of the coils until the voltage at the source pin of TR5 reaches zero. You do not have to be really accurate with this, as you can adjust the GEB control to compensate.
Next, if you re-measure the voltage at the output of the pre-amp, it will not be zero. This is normal. Tesoro coils have a residual voltage of about 15mV, which results in around 600mV to 700mV at the pre-amp output.
If the discrimination rejects non-ferrous instead of ferrous, then flip over the RX coil connections and start again.

[simonbaker]

Dear Sir
thanks for replying me
i have made a test of nulling coil as you described for me
but i couldnot get less than 4.7mv
i spent half a day before it was easy to null as Ivconic way only few seconds
but honsely i belive in your way in nulling but dont tell Ivconic he gets angry very soon
lets see what i done i put 100k GB resistor on mid position
and put a -lead on body and
+lead on pin7 of LF353 is it right??
please if you dont mind explain for me i know you reported many times
just this time again please by the way the result was around 10cm for silver coin 1.7cm ..
Dear Qia the 100k GB is around 96k i tried to get exact value but i could not cuz of resistor tolarance

thanks alot

It is not easy to understand exactly what you are doing. GB resistor is not part of nulling procedure (I think).

and put a -lead on body and

Do you mean ground?

but i couldnot get less than 4.7mv

That voltage may be OK.

But please do this experiment. Try changing coil positions until you get the maximum distance for detection of coin. Then tell us what the distance is and what the voltage at pin 7 is.

- Are you using oscilliscope or voltmeter?

- Do you have a digital camera? I would like to see pictures of your coils, cable, PCB, and oscilloscope images.

Don't give up. It takes patience and experiments. Just ask Ivconic.

Regards,

-SB

[ivconic]

It is true. I added many decoupling caps there to improve more S/N ratio on that pcb. And yes..indeed; that pcb is really the best so far!
Dont worry - just put those caps there and enjoy!

[metaldetector107]

Replacement

Dear Ivco
i have nothing more than TGSL i am dreaming of it everyday
yes of course because i am run out of 2n2222 and 2n2907
thanks
by the way i made your last TGSL PCB only but some caps values
are deffrent from the schematic example
on .lay there are many 0.1uf but on schematic only one any help