TESORO GOLDEN SABRE

[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,
Thanks.

[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

[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.

[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.

[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!

[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.

[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.

[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.

[nelson]

Thanks to everyone.
My new coil has the same data has yours Ivconic. Noew i gain a few more cms (24 for a 26mm copper coin)
I also place new LM308.
The coil was nulling with the scope, no problem:
Now i m focusing on cable. I m using usb cable, but i have heard that this is not good for VLF detectors. So what capacity should i use , lower or higer?
Ivconic, this weekend i ll try to open my Gold Bug2. This is also important to me cause i whant to know if is possible to mod the detector to allow full discrimination, instead of fix discrimination (all metal/iron reject).
Regards
Nelson

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.

[ivconic]

Usb? Dont know. Maybe it is not so suitable to be used there? I am not sure.
Search net for Belden cables, explore its specs and try to find simillar one...already proven as very good to be used here.

[nelson]

Ok, thanks Ivconic. I ll do the search.
regards
Nelson

Usb? Dont know. Maybe it is not so suitable to be used there? I am not sure.
Search net for Belden cables, explore its specs and try to find simillar one...already proven as very good to be used here.

[Qiaozhi]

Homemade coils

At last I've found some time to test the overlapping coil configuration that most of you are using to build your homemade coils. The Tesoro factory-made concentric coils are all constructed to provide an initial phase-shift between the TX and RX of about 120 degrees, with the RX signal measured at the output of the RX preamp. All targets give a phase-shift to the left, with ferrous targets causing a decrease in amplitude, and non-ferrous causing an increase.

I constructed a simple test using two round coils of 180mm diameter. The TX coil consisted of 115 turns of 0.56mm enameled wire (5.6mH) and the RX had 122 turns (6.5mH). I was really trying for 5.9mH on the TX, but this discrepancy will not affect the test.

To get the correct 120 degree phase-shift between TX and RX, it is necessary to gradually move the two coils together until you reach a null point, and then go through the null until you have a few mV at the RX input. You can find the null point more easily by monitoring the preamp output with a scope. In this position, ferrous objects will cause a decrease in amplitude, and non-ferrous will cause an increase. However, all metallic objects will cause a phase-shift to the right. This is, of course, different to the concentric coils, but because of the way this type of analogue detector works, the direction of phase-shift is not a problem.

After some experimentation with this test setup, it is clear why Tesoro deliver their detectors with concentric coils. Has anyone tried constructing an omega coil for the TGS? I would think that the omega would be much easier to set up than the concentric, and may perform better than the DD.

[tiktak]

Hi,

Hi,
Max.
Its look like I havent solved the probleme afther all!
Still this week beeeeeeeeeeeeeep all the time.
The 22 ohm resistor were burned and I replaced it but this didnt solved the probleme.The funniest thing is that this morning I bwol air against the PCB from the left short side and this sound stop.But afther a while it begins again.What is this?
Also I have used your pictures and make the same coil but when I attach TX to PCB the frequency is 28,2 kHz???????Why?
Please check the numbers again!I see:11,4;12,5;12,75;13,35;13,7 and 1,6cm~!~~~
Right.
Tx=100w 0,25
Now I have cheked on my old PCB also around this frequency but working desent.
Hum......................

[Qiaozhi]

Hi,
Max.
Its look like I havent solved the probleme afther all!
Still this week beeeeeeeeeeeeeep all the time.
The 22 ohm resistor were burned and I replaced it but this didnt solved the probleme.The funniest thing is that this morning I bwol air against the PCB from the left short side and this sound stop.But afther a while it begins again.What is this?
Also I have used your pictures and make the same coil but when I attach TX to PCB the frequency is 28,2 kHz???????Why?
Please check the numbers again!I see:11,4;12,5;12,75;13,35;13,7 and 1,6cm~!~~~
Right.
Tx=100w 0,25
Now I have cheked on my old PCB also around this frequency but working desent.
Hum......................

Hi Tiktak,

First - I would check all your power supply voltages, not just at the output of the regulators, but also at the power pins of the ICs, in case there are any wiring errors.
Are all your ICs in sockets? If so, then this could easily be the cause of your problems. In particular, the comparator IC should not be socketed. In the TGS circuit, the comparators are responding to relatively slow input signals that tend to hover around 0V. This can easily cause the comparators to go into oscillation. Try monitoring the comparator outputs with a scope to see if this is happening. These oscillations can be avoided by soldering the IC directly to the PCB (not using sockets), by using good PCB layout techniques (ground plane under the IC), and/or by adding a capacitor across the input terminals. A value between 100pF and 1nF should be sufficient. It may even just be a case of adding a 100nF decoupling capacitor across the power pins. If all these methods fail to remove the oscillations, then you will need to add some components around the comparators to provide hysteresis, although presumably the original TGS does not suffer from this, and it really should not be required.

Of course, this may not be the cause of the problems, but that's where I would start my investigation, after checking the power supplies.