TESORO GOLDEN SABRE

[ivconic]

Indeed. "Wildly" adjusting GEB trimmer there will affect phase to much.Not comfortable and easy in real conditions on the field.Operater must pay a lot of attention on pot. position.

[Qiaozhi]

So... how i can tune my RX coil to 16.12 Khz?
I m not very skilled with the scope jet, so please explain moregraphically.
Regards
Nelson

Hi Nelson,

The RX coil will be tuned to 16KHz if your coil is 6.5mH and the tuning capacitor is 15nF - that's all. Regardless of the resonant frequency of the tank circuit, the RX signal will be the same as the TX, so you cannot check this on the scope. Simply measure the RX coil inductance to confirm the correct value.

[Fred]

Hi,
I have put the GB pot on front panel, but used a good quality pot and coax cable .I works OK, but as Ivconic said no much point unless you want to change coils all the time

regards,
Fred.

[ivconic]

"Ground balance?

Could this be my problem with deep?

Ivconic, can GB pot place on front panel?

In advance many thanks
Nelson"

I dont think so. GEB does not have some influence on "depths" in air tests.
You can put it on front panel but no benefits from that. Actually it is not usuall GEB preset to be adjusted oftenly. Better to adjust it once and good and leave it inside for good. Depth problems are usually related with coil specs and quallity of nulling.
Regards!

[nelson]

Ground balance?

Could this be my problem with deep?

Ivconic, can GB pot place on front panel?

In advance many thanks
Nelson

Hi,
I have just tried my new DD coil, here are the results.
All tests where made in air, with a 1 dollar coin,38mm diameter.Coil is 20cm diameter

When at maximum,the "sens" pot is at 5 o´clock, here i get a few random beeps,i reduce it to 4 o´clock and it is perfect.
-With ground ballance pot a one side (no ground balance),all metal,i could detect the coin at more than 45cm!! With sens at max, barely detectable at almost 50cm. I had to fix the coin on a 1m plastic pipe to avoid detecting my hand.
-With GB properly set, all metal,38cm.
-"Disc" on , 27cm

Now i want to put the GB pot on the front , i let a space for this.
The TGS i really an excellent detector!

Thanks for all who helped here to build it , in particular Qiaozhi,Max,Ivconic Etc.
If i find a treasure i will let you know
No i am going to build to the next project, a PI.
Best regards to all! ,
Fred.

[nelson]

So... how i can tune my RX coil to 16.12 Khz?
I m not very skilled with the scope jet, so please explain moregraphically.
Regards
Nelson

Hi Molzar,

For the TGS, the TX frequency should be 14.65KHz and the RX must be tuned to 16.12KHz. So it's important to note that the resonant frequency of the RX circuit is higher than the TX. This might be causing the right-shifting of the phase if the RX frequency is lower. Otherwise, there is no reason why the DD and concentric should react differently, unless it's something to do with the physical construction. i.e. under or over-nulled.
Perhaps you could experiment with your setup, and let us know the results.

[Aziz]

Hi all,

during looking into LC oscillators deeper, there is a potential for improvements for TGS. The signal from the LC oscillator should be bufferd with a simple transistor (impedance conversion) and from this it should be fed to the four destinations. This would improve the frequency and phase stability of the LC osc. As this is the main important part of the MD, it should make the detector more stable. Just try out.
Aziz

[tiktak]

Hi,

Hi,
Thanks.

[Max]

Hi,
Ok.
Max I will try!But what you mean buy swap?Change new with NEW?
Right?
Thanks for Help

Hi,
no... you can change one at end of chain with another that is before it... same type of course.

You can also try new parts there if you have handy.

Kind regards,
Max

[tiktak]

HI,

Hi,
Ok.
Max I will try!But what you mean buy swap?Change new with NEW?
Right?
Thanks for Help

[Max]

Hi,
Max.
I am using only brand new parts!
But I have went today and buy all again.This time I found 10mTANT and metal case 2N2222!
When cheanged all looks cool now NO heating! I probaly have turned 2N2222 wrong way and my PCB werent cleaned good!
Now BATT check is ok!I can detect metal very poor performance for now.But we will change this.The probleme is that there is constant week sound.More like treshold.But I dont here this on my first device!Why?
I am using now TL081 insteed of lm308 and TL082 insteed of TLC2262.
Can this be the source of this noise?Or its just bad coil?
Thanks for your help.

Hi,
sure new parts... are better, but there's a problem with new parts also... so when I say "old" this would mean different things: some shops and dealers buy e.g. electrolitic capacitors in huge stocks (thousands of them all same value) and this just with slow process... that sometimes require also 10years from one order to the other...

If so... you buy "new" parts (at least you think so) but then the seller give actually you a 10years old product (yes, could happen easy in some places... and with some dealers...expecially when you find this stuff at very attractive prices...). Since ESR and drying don't know the difference between staying on the shelf or not... BUT knows very well that time goes by... you could buy "new" stuff with fairly low ESR.

Also... if you live in an hot place or really humid in some part of the year you could be sure , unless you buy stuff really made in around 1 year before not more, you got degradated ESR parts.

This was a cause of lot of troubles in old CRT TV sets (and also some newer) cause people sometimes don't have enough understanding of what's an electrolitic cap and that they MUST avoid putting TV in the kitchen or bathroom to keep working the TV and avoid rapid ESR derating...

Now cause some dealers are like users that put TV in the bathrooms... you can be sure you could buy bad caps, even "new", from them...

Anyway... the threshold sound you hear is strange too... try swap op amps starting at audio section and see what happens...

Kind regards,
Max

[tiktak]

Hi

Hi,
Max.
I am using only brand new parts!
But I have went today and buy all again.This time I found 10mTANT and metal case 2N2222!
When cheanged all looks cool now NO heating! I probaly have turned 2N2222 wrong way and my PCB werent cleaned good!
Now BATT check is ok!I can detect metal very poor performance for now.But we will change this.The probleme is that there is constant week sound.More like treshold.But I dont here this on my first device!Why?
I am using now TL081 insteed of lm308 and TL082 insteed of TLC2262.
Can this be the source of this noise?Or its just bad coil?
Thanks for your help.

[Max]

Hi,
Max.
Thanks for the fast reply!
I will check all!The fets are the same as on my previous device BF245C.
I am using test coil,so maybe this is the probleme!
Yesterday I have played again with device.I were prety shore that I have burned something.But I found point where I have responce to hugh metal so.............
What could be the probleme there?I will serch buy your leads.
p.s.the main probleme is that this LM358 near BC517 is heating and bc517 too.When I turn on.But some times they dont.Realy confused here.
I cheked the voltages just to make shore there is power and I think they were ok!But dont remember exact values.Will chek again and tell you.
Thanks.
The strangest thing is that I dont have same batt check like on first device!Now its have different voice.I use same parts.And some time batt chek dont stop at all,other time dont sound at all??

Hi,
look at the 10uF capacitor... it's new part or did you use some old one there ? If dryed it could expose bad ESR (equivalent series resistance) enough to make your fet there stay sometimes/always on or off and thus giving confusing behaviour.

The fact 517 is running hot depends on fact it stay on for too long time... and current there flow, as it should, hi cause of driving the speaker. To reduce the problem mount a smaller speaker as temporary with say something 25-50 ohm impedance (some scraped from an old headset/headphones could be ok)... this way you'll save the 517 from thermal runaway when still trying to understand where problem is.

The LM358 hot seems, instead, a bad sign... probably means device is burnt already : look carefully at tracks for small solder joints or "ball" between legs if any. If you'll find fault there it's probable you need a new LM358 to replace the damaged.

Kind regards,
Max

[tiktak]

Hi,

Hi,
Max.
Thanks for the fast reply!
I will check all!The fets are the same as on my previous device BF245C.
I am using test coil,so maybe this is the probleme!
Yesterday I have played again with device.I were prety shore that I have burned something.But I found point where I have responce to hugh metal so.............
What could be the probleme there?I will serch buy your leads.
p.s.the main probleme is that this LM358 near BC517 is heating and bc517 too.When I turn on.But some times they dont.Realy confused here.
I cheked the voltages just to make shore there is power and I think they were ok!But dont remember exact values.Will chek again and tell you.
Thanks.
The strangest thing is that I dont have same batt check like on first device!Now its have different voice.I use same parts.And some time batt chek dont stop at all,other time dont sound at all??

[Molzar]

Hi,
Ineresting.
We asumed here 14kHz for optimal!
So strange if TGS work fine in such wide area?
But what is best here?

Tiger Sharks operate Freq is 12.5kHz, not sure if this is same coil as one for Tiger Shark (that why I ask), suppose to be old land based coil.

Freq when hooked to my TGS is ~ 14.5kHz.

Molzar