TESORO GOLDEN SABRE

[kt315]

Merry Christmas amigo

[ricalbertvig]

hello .. I finished mounting the pcb .. I have a problem ... to put tx generates a permanent noise audo .. what can be the cause?

[kt315]

this schematic is not working right without coil - no second/negative rail voltage. do a dummy temporary coil with 6mH (milli-) and connect
it to TX.

[ricalbertvig]

the problem is when putting the coil, permanent noise without being able to control the audio .. without coil there is no audio

[ricalbertvig]

I was able to solve the problem ... it was the 8v regulator .. I was giving a 3v output .. it restores everything right now

[Ozoz_xba]

Something strange here .i make an 27dd new coil.nulled at 2.2mv ,in all mode .when tested in all mode it works good but disc mode doest work.it rejects all the coins and only the ferroes beep,it should rejects them but it beeps.on the concentric coil the circut worked good at disc mode.now in dd coil the frequency is 15.5khz��

[Ozoz_xba]

I should get 4mv on rx and try it again if disc is working.
By the way my tx and rx is made by 0.45 wire...

[waltr]

Something strange here .i make an 27dd new coil.nulled at 2.2mv ,in all mode .when tested in all mode it works good but disc mode doest work.it rejects all the coins and only the ferroes beep,it should rejects them but it beeps.on the concentric coil the circut worked good at disc mode.now in dd coil the frequency is 15.5khz��

It is not simply the RX Null Voltage --- it is the PHASE difference between the TX and RX that determines the discrimination.

It is much better to use a two channel O'scope when adjusting the coil NULL.
Set the Null so that the RX wave lags the TX by about 20 degrees.

Second, I assume you wound the TX and RX coils with about 0.5mH difference in inductance. This is also critical to obtin the correct phase shift and have discrimination work.

Last is to have the polarity of the coils connected to the TGS correct.
Possible you simply have the RX coil connected backwards. Try swapping the only the RX coil leads.

[Hyena]

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...

It is not simply the RX Null Voltage --- it is the PHASE difference between the TX and RX that determines the discrimination.

It is much better to use a two channel O'scope when adjusting the coil NULL.
Set the Null so that the RX wave lags the TX by about 20 degrees.

Second, I assume you wound the TX and RX coils with about 0.5mH difference in inductance. This is also critical to obtin the correct phase shift and have discrimination work.

Last is to have the polarity of the coils connected to the TGS correct.
Possible you simply have the RX coil connected backwards. Try swapping the only the RX coil leads.

[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

[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]

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?

[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]

[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]

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?