TESORO GOLDEN SABRE

[kt315]

W. Lahr did mistakes in every his sketch. i wrote that billion times. you must YOURSELF check every component
desoldering it off the board. just then you will see right schematic.

[ivconic]

Probably somebody before "iwkonik" did that, not me.
Truth is that there are 4.7k and 47k on same place at different versions of W. Lahr retraced schematics.
I just checked my archive and i found out that there are several versions of the same schematic, done by somebody else, much before me started to grow interest in those.
However; there is not trouble with TGSL.
So many people did it so far with success.

[kt315]

walter
Don Bowers' schematic has fatal mistake in TX colpitts oscillator. look on my right sch of Cobra and you will see R3 is NOT 47k -!
(R10)
somebody (iwkonik?) losted the decimal point.

[waltr]

hi Ivconic
thank you for all that information you post on geotech
i decided to make TGSL detector(schematic in Don Bowers guide) so first i test the schematic
on bread board by using high quality components but it did not work!

A bread board may have too much stray C. It should work somewhat.
I prototyped the TX oscillator on a PCB prefboard and that worked first time. I use this to test coils looking for the frequency they oscillate at.

coil information : TX = 6mh(25 ohms) and Rx = about 6.5mh(26 ohms)

Prototype just an oscillator and check each of the RX & TX coil on the same oscillator circuit as Dbowers recommends in his 101.pdf. The RX & TX coils need to oscillate at a difference of about 550Hz.

but i only get 7 Vpp of amplitude for the best which is reasonable for +8V supply but not 16V(i don't know how it is even possible to get 16V out of +8!!!

The one I built has about 16Vpp output.

so my question is: what schematic do you guys use in order to make it work???

I used the EDU schematic which is the same as in Don's 101.pdf but simply bought that PCB from SilverDog.

https://diydetector.co.uk/store/index.php

my rx frequency are the same as tx(14.5 KHz) and i can't change it

Of course RX measures the same Freq since it simply Receives the TX.

There is a whole sub-forum on the TGSL here:

https://www.geotech1.com/forums/forumdisplay.php?18-Silver-Sabre-Bandido-TGSL

Lots of post about getting this circuit going.
It is one of the easiest VLF circuits to build but still has many subtle pieces that must be correct.

[kt315]

leave it out. buy a board from russian and do normal project, без косяков. you'll get only trouble with tgsl.

https://www.ebay.com/itm/Metal-Detector-Tesoro-Lobo-DIY-ONLY-PCB-1pc/184122294712?hash=item2ade8b41b8:g:7pEAAOSw1r5bW2U6

[Mr.Jaick]

hi Ivconic
thank you for all that information you post on geotech
i decided to make TGSL detector(schematic in Don Bowers guide) so first i test the schematic
on bread board by using high quality components but it did not work!
coil information : TX = 6mh(25 ohms) and Rx = about 6.5mh(26 ohms)

i tried to troubleshoot the circuit and found out that TX circuit does not work anyway
why? because transistor colpitts oscillator(tx circuit) won't work without collector load and base bypass capacitor, in this case(this is a common_base amp) so i added a 10k pot between collector of 2N2907 and ground and a 220nF cap between base and +8 supply rail and it worked, no surprise
but i only get 7 Vpp of amplitude for the best which is reasonable for +8V supply but not 16V(i don't know how it is even possible to get 16V out of +8!!!
since it's a oscillator not a voltage doubler)
so my question is: what schematic do you guys use in order to make it work???
i,ve tried many times with "original" and even different designs but it's not working at all.
and my own design is not working as it supposed to in that makers guide(Don Bowers)
i,m completely disappointed whit this project and kinda wrong information
my rx frequency are the same as tx(14.5 KHz) and i can't change it
so please help me if you don't mind, thank you very much

[Ozoz_xba]

Interesting material this GEM. Found info:
https://www.erico.com/category.asp?category=R2387

Yes its the material that they make the graphite spray and sell back to you x1000��

[waltr]

Interesting material this GEM. Found info:

https://www.erico.com/category.asp?category=R2387

[Ozoz_xba]

Thanks for explanation of how you got the DD coil to work well.

Let me re-state to ensure I understand:
Old DD coil used thicker wire (0.45 mm diameter)
New DD coil used thinner wire (0.25 mm diameter)
Thinner wire results in higher resistance.

What did you use for coil shield?

My tx 0.25 wire (25ohm) and rx 0.45 wire (12-13ohm),rx coil 1 cm bigger in diameter than tx, for shield i have used GEM(ground enhancement material) maked it likuid and get outside the coil glued,its 200ohm everywhere,but i have not put it in my board circuit yet,i will put tomorrow.This GEM i have used before in my concetric coil and no false signals had in my detector ,very good,i search in silent in every earth condition ,becouse the grafit has about 60kohm ,i ptefer to use GEM which i can arrange its ohm as i like...for me 200ohm is best and hard to get in shield.
An exmple of my concetric coil with GEM how it looks

https://i.hizliresim.com/YdYnmz.jpg

[waltr]

Thanks for explanation of how you got the DD coil to work well.

Let me re-state to ensure I understand:
Old DD coil used thicker wire (0.45 mm diameter)
New DD coil used thinner wire (0.25 mm diameter)
Thinner wire results in higher resistance.

What did you use for coil shield?

[Ozoz_xba]

[QUOTE=waltr;265746]Great your new DD coil is working.

have made my DD coil now go deeper in air test,1 euro about 36 cm horizontally and about 16-20 cm vertically,about 2.1mV nulling,tx at 14.5khz rx at 13.7khz(putting at tx).discriminate is very very good .in air tests can take 1 euro puting up to pliers in all mode (pliers rejected) from a distance of 17cm.with consentric coil (txand rx 0.45 wire made) i didnt get that .first of all i have make a new tx 0.25 or 0.3 wire (looks like 0.25)(25.2ohm),putting it at tx arranging 14.5khz ,(my DD coil is 27 cm outside).after i had rx at 13.7 khz(putting at tx) but with wire 0.45,(12ohms),my rx is 13.5 cm x25.5cm the tx id 1cm lower 12.5x25 cm,i put them on my coil dd cab and put also my voltmetre at rx+in board and get at the same time the best nulling which 1 had at 2.1mV ,at the same time i chevked with coin and ferroes.0.45wire rx and 0.25 wire tx(1cm lower than rx in diameter) worked very well,didnt exspect get that result in fact.before get those result my tx and rx was 0.45 wire made and i get just 20cm in air for 1 euro max,but now its good to have it deeper.i advice you all to do those coils.by the way i have no oscolloskope ,never used it from the begining of pcb dedector.i used just 1 multimetre (voltmetre),which also had an frequency meter on it. First test.

https://youtu.be/xxsBFH4geHs

Best regards

[waltr]

Great your new DD coil is working.

I only have a 25cm DD for my TGSL.
However, I have both a 25DD and a 20concentric for my OI detector. The 20Concentric goes deeper.

Don has say this to me that the 20 concentric he has build go deeper than the 25DD on the TGSL's he has built.

https://sites.google.com/site/dbcoilshells/home

Reason I come up with is a DD only has a narrow 'slit' and therefore does not go as deep. Advantage of the DD is you can cover a larger area of ground with each sweep. I like that feature, on both TGSL and PI, for park and sport field hunting so I can cover ground faster and most target are not that deep anyway. With the PI I use the 20cm concentric for relic hunting. I do have plans to build a 20cm concentric for the TGSL, just haven't gotten to do it yet.

[Ozoz_xba]

Thanks to all.my DD coil get nulled at 6.1mV,i used the coin&ferrite method to null it.i got ferrite rejected at 6.1mV and disc worked well,but the xoin in air just go about 22 cm (tx 0.45 wire working at 15.5khz and rx (0.45 wire)at tx is 14.5khz),should i look for tx 14.5khz and rx at tx 13.9khz for more deep for 1 coin?infact the coil on consentric is performing better than DD about 32 cm in air for 1 coin and frekuency is 1khz lower than DD,does 1 khz make so much role in deepnes for a coin?

[Ozoz_xba]

Thanks for your advice i will play with caps.i have tx at tx frequency 15.5khz and will make rx now putting on tx at 14.9khz using the caps and puting that caps on rx with 15nf and see what happened

I had an concetric coil repaired and tested to the board.yes it works well as it eas before.that means that the circuit works now so i should focused on DD now��.get the best nullimg

[Ozoz_xba]

In my excperience, null (voltage nor phase) does not affect GB nor Disc range.
Its Rx resonant frequency, which affect this.


Regardless on coils and oscilator you use: Measure precisely Tx frequency.


Now you have 2 options:


1) Coil tester: Use coil tester with your Rx and Rx cap. Hit Rx frequency to be 1,11 * Tx frequency.
2) Inductance measurement: precisely measure Rx inductance - calculate Rx capacitor value to Rx reach 1,11* Tx frequency.


Does not matter what way you choose. Does not matter on null. Only resonant frequency ratio matter.

Play with it a little and you will see...

Thanks for your advice i will play with caps.i have tx at tx frequency 15.5khz and will make rx now putting on tx at 14.9khz using the caps and puting that caps on rx with 15nf and see what happened