TESORO GOLDEN SABRE

[Max]

Hi Max. Great work.
I will check the photos with mine and i will write the results.
For start.........
The out of LF353 is 800mv p-p. The 353 has a gain of 220/5.5=43.1 , so the input voltage or the coil out is 800/43.1=18.5mV. This is the out voltage of your coil after null. At my detector the voltage is 150mv p-p (maybe better null).
When i play with disc pot i have a phase change of about 80degrees, but you have about 40 degrees. Why???????
Ok you will tell me that your detector works ok and mine don't discriminate good, but this is an other story. I connect the channel1 at the Tx coil so maybe to be this the reason. I will try it later with same connection with you.
But you have a problem near the LF353. Ivconic said that it is exactly the same if you put TL082. So if you have one check it.
Regards

Hi Geo,
you are about right on coil, I've used one DD nulled at 15mVpp on scope to make test cause I cannot dismantle the DD255/137 I actually use from pole at now.

It's glued down on a piece of wood.
Actually there isn't any great attenuation of sens... but I use better nulled coil on real soil due to GEB.

With TL072/TL082 instead of LF353 the things are all the same same ringing at pin 1... all the same.

Kind regards,
Max

PS: coil use Ivconic's specs

[Geo]

Hi,
not on TGS, I've made on bandidoII... well works... but I respected original Tesoro's design and haven't put cap inside coils... so now I can use bandidoII coils on TGS too.

It's your choice... I cannot see any real advantage on these designs doing so.

Best regards,
Max

Hi
Generally is better the transfer cable to be connected to a tuned circuit than to tune after the cable. Always theoretically

[Max]

Hi Ap and Geo,
from what I know there are only 5 manifacturers of LF353:

- National
- Motorola
- STM
- Fairchild (but really obsolete now... and almost impossible to find)
- Texas Instruments

I've National's ...what's yours ?

Kind regards,
Max

[Geo]

Hi Max. Great work.
I will check the photos with mine and i will write the results.
For start.........
The out of LF353 is 800mv p-p. The 353 has a gain of 220/5.5=43.1 , so the input voltage or the coil out is 800/43.1=18.5mV. This is the out voltage of your coil after null. At my detector the voltage is 150mv p-p (maybe better null).
When i play with disc pot i have a phase change of about 80degrees, but you have about 40 degrees. Why???????
Ok you will tell me that your detector works ok and mine don't discriminate good, but this is an other story. I connect the channel1 at the Tx coil so maybe to be this the reason. I will try it later with same connection with you.
But you have a problem near the LF353. Ivconic said that it is exactly the same if you put TL082. So if you have one check it.
Regards

[Max]

Hello Ivica.

Made a testboard, giving me also some problems. If I pas my hand over the print it wil give an echo..... can be becorse of the long connections.?!
Can also be a problem in the desing from the print.......?!
If I pul out the zener 4v3 I got the same signal at 353-1 that you have, look at the screenshot.The transmitsignal has so also some effect.

The first board is working fine, it is the test board that gives problems, wel wil check and test tings, if answers are there I let you know.

Ap

Hi,
my signal at pin1 is exactly the same as this your last one.

I don't understand exactly why... but I think it depends on LF353 type.

Did you use the same part for the previous test (perfect sinus) or is a different LF353 there ? What's brand of first part you tested and what's second if different ?

Also Geo has a perfect signal on pin1 and that's again strange having such different behaviour from one board to another... using always LF353 there !

My guess is that there is some difference from some lf353 to others that make damped osc appears...

BTW I've a National LF353N on circuit... and it give me damped oscillations like I see in your last post...

Kind regards,
Max

[Max]

Hi Max. I have not a 1Euro-cent to try, so i found at my Lab a old bronze coin (unknown) 7mm diameter (yes it is very small). I detect it at 20...22cm. I don't say you for sure 22 or 20 cm because at full sens as i wrote before i have some parasitic signals.
Regards

Hi,
yes I detect at some more cms but maybe cause coil is 10'' so field density is different.

I think that's ok for a DD32cm diameter round getting very little stuff at a bit less depth.

Best regards,
Max

[Max]

For Ivica and Max.
Do you tried to connect the Rx capacitor (15nf) at the wind of coil before the cable (from coil to detector)
Regards

Hi,
not on TGS, I've made on bandidoII... well works... but I respected original Tesoro's design and haven't put cap inside coils... so now I can use bandidoII coils on TGS too.

It's your choice... I cannot see any real advantage on these designs doing so.

Best regards,
Max

[Max]

other pics....

[Max]

other pics...

[Max]

Hi all,
early this morning I've made all the stuff... test-points map and pictures... very hard work cause I had to dismantle board... and I need in next few days... so now I have to reassemble again...

anyway, here we are ! A full set of traced signals from TGS.

I still have the problem at LF353... but cause Geo and Ap haven't in some of their measures I strongly suspect problem is related to my LF353 cause came from an old stock of parts, thought it's new and never used before.

You can see that problem occourrs just on pin2 of 353... where are dumped oscillations you can see clear in one picture.

I hope that's enough... cause otherwise I have to dismantle again and that's not so funny!

In the map you can see where test-points are an index for each signals, in the list you can see explaination of figures and references to measured signals.

Kind regards,
Max

[Geo]

Hi Geo,
fine. If you tune coil and it's 32cm diameter you'll get more depth I think.

As you can see the TGS circuit is good for depth with small things... much like some PI detectors with small coils!

My only thoughts are about sensitivity to very small objects like 1eur-cent sized things... maybe the 32cm coil would detect them at lower distance cause of field shape/density.

Let me know.

Kind regards,
Max

Hi Max. I have not a 1Euro-cent to try, so i found at my Lab a old bronze coin (unknown) 7mm diameter (yes it is very small). I detect it at 20...22cm. I don't say you for sure 22 or 20 cm because at full sens as i wrote before i have some parasitic signals.
Regards

[Geo]

For Ivica and Max.
Do you tried to connect the Rx capacitor (15nf) at the wind of coil before the cable (from coil to detector)
Regards

[Geo]

Hello Ivica.

Made a testboard, giving me also some problems. If I pas my hand over the print it wil give an echo..... can be becorse of the long connections.?!
Can also be a problem in the desing from the print.......?!
If I pul out the zener 4v3 I got the same signal at 353-1 that you have, look at the screenshot.The transmitsignal has so also some effect.

The first board is working fine, it is the test board that gives problems, wel wil check and test tings, if answers are there I let you know.

Ap

Hi Ap. I have a problem like your........
Sometimes when i touch the pcb or the coil housing or any wire i have erratic signals (beep...beep...etc). Other times it works ok. I think that it must be shielding problem. If i will find it i"ll write you. I must go out to test it (when rain stops) because i am afraid that at my Lab there are a lot of parasitic signals.
When the box with the pcb is at a position with the potentiometers to look the roof then i can put the sens to "7"position". But if i rotate the box with pcb 90degrees then i can put the sens at maximun.
What to say???
Regards

[Qiaozhi]

"...I think that you probably have some other and bigger problem that mask the positive effects of having it.

That's why you cannot see advantages... or maybe is just simulator that make us crazy now..."

Most likely i do!

But also possible other??? I never liked simulators...many times results from them do not correlate with reality!!! Plain truth!

This depends on how proficient you are with a SPICE simulator. As with any computer program - "rubbish in, rubbish out".

[ivconic]

Final notes

I reac the point where can say that i am very satisfied with TGSL, after a lot of effort involved and lot of problems so i'll rather make final conclusion and stop thinking about this anymore. Further i'll take a part in this discussion only when some new mod occurs....

Conclusion:

TGSL is working PERFECT in All Metal and DISC mode. Neither one false signal even if i swing, bend or anyhow "torture" cable and coil.
I am not using 1M resistor any more. I am not using any extra resistances in serie with speaker any more, cose i changed resistor 2K2 (33K) with 10 K resistor. Although lowest resistance i can suggest here is 8K2...Experiment and you will see. I can freely lift Sense pot to "9" at All Metal mode or "10" to Disc mode without chance to face any false signal at all.
In Disc mode when Disc pot. is at minimum - "0" it is still stabile and calm. Discrimination is perfect...
Only thing that bug me is weak audio but this has nothing to do with present setup. It will need some mod to have louder tone.
At front end i put again LF353 just to respect original setup, but aint no difference if i put TL082 too. Works same.

- 2cm coin at 40cm in the air (AllMetal) and 37cn in Disc mode..
- Cola can at 85cm in the air (AllMetal) and 80cm in Disc mode...
Stabile,stabile,stabile...all i ever wanted from detector..
At the end it showed that oscillogramms i posted here (latest one)are accurate-no mistakes at all...

That is all from me.
Next thing i am interested would be audio mod....but now i'll take rest for few days...
Regards!