Tesoro Lobo news

[Legaucho]

Hello all

I worked last night on suggestions of Qiaozhi and to Porkluvr

Tests with the basics of Qiaozhi, gave permanent instability. Capacitor .01uF on TX ok, but the same value plus some adding on RX make the trouble.

Tests with the basics of Porkluvr, allowed to have a threshold interresting (I have one on TX .01 uF capacitor in parallel and 590pF, one .0033 uF capacitor one RX).

I confess I did not continue further because I was tired of my day.

But I have another question which has me pure novice I can not answer: What is the role of C7 and what should be its value? (see attached diagram).

I could not do testing for over a week because I must take time off.

[Qiaozhi]

It's a pity for me because I don't have scope

It would be a good investment to get one.

[Legaucho]

Many thanks Qiaozhi andporkluvr for your answers rich in interest.

I wil try this evening the capacitors change.
Concerning the Fisher coil I made an extension cable to be similar with the connection on the Lobo.

I use this schematic http://www.geotech1.com/forums/attachment.php?attachmentid=18453&stc=1&d=13289041 55
It's a pity for me because I don't have scope

[porkluvr]

First change the 15nF on the TX to 10nF. This will give you 20.5kHz. which should be close enough. As a "calculated guess", I would also replace the 4n7 cap on the RX with a 10nF. If the residual voltage and phase are incorrect, then try adding a few pF across the RX cap until you get the right values.

As porkluvr says, you'll really need a scope to do this properly.

AND we also need to see the exact same schematic as what you are working from and know about any deviations from what is shown, otherwise we are just barking at the MOON.

edit: Maybe I should speak for myself. I didn't mean we, I meant me. I would really like to see what you have built before I try to tell you how it should be modified. I mean, there are about 5~8 different versions of Lobo "clones" floating around. Which schematic did you use?

[Qiaozhi]

Hello

The caracteristics of the Tesoro 9'x 8' concentric coil:

RX = 6.54mH ( 24.9 Ohms )
TX = 6.03mH ( 26.1 Ohms )

Good news, my first try was not not so bad, no mistakes on PCB and all function is running, I must finalize the discrimination, I am currently on :

RX stage one 4.7nF capacitor and on TX stage one 15nF capacitor. Can someone help me refine these parameters to obtain the initial 20 kHz of the detector.

First change the 15nF on the TX to 10nF. This will give you 20.5kHz. which should be close enough. As a "calculated guess", I would also replace the 4n7 cap on the RX with a 10nF. If the residual voltage and phase are incorrect, then try adding a few pF across the RX cap until you get the right values.

As porkluvr says, you'll really need a scope to do this properly.

[porkluvr]

Legaucho, what do you have in the way of test equipment?

You need to choose between either using the factory coil which was designed for a different machine, or the home made coil which may or may not be properly aligned. And we need to know what you have in the way of test equipment before you will get any good advice.
Just my opinion.

The Fisher coil probably has the wrong connector so shouldn't you forget about that, at least for now?

It is relatively easy to figure out how to find a capacitor to tune a TX coil to a particular frequency, but it will be much more difficult to align the receiver phase to the correct angle for your ground and discrimination channels to work correctly. I really hope you have a dual trace oscilloscope.

edit: For the 6.03mH tx coil you should use a .01uF capacitor and about 600pF in parallel to tune to 20kHz. If you can, select a .01 that is slightly high and then you won't need a parallel capacitor.

edit: With the 6.54mH rx coil I think you should use a 3nF capacitor in parallel. That should give you approximately the same phase as what a 10mH coil (with no parallel capacitor) would.

[Legaucho]

Hello bernte, again me

I have also two other coil, I can try it

One DD homemade coil

RX = 11.14mH ( 51.9 Ohms )
TX = 1.68mH ( 9.5 Ohms )

One DD Fisher coil

RX = 7mH ( 38 Ohms )
TX = 0.67mH ( 2.4 Ohms )

[Legaucho]

Hello bernte,

I have mesuring those caracteristics on my coil ( it's a first generation coil ).

[bernte_one]

hello

the last coil i buy was for cibola, vaquero, lobo supertraq
combination of 1mH and 16mH
are you sure you have the right coil?

you can caculate frequency
when you now inductivity and caps for the coils

regards

[Legaucho]

Is that a 20Khz coil?

Hello

The caracteristics of the Tesoro 9'x 8' concentric coil:

RX = 6.54mH ( 24.9 Ohms )
TX = 6.03mH ( 26.1 Ohms )

Good news, my first try was not not so bad, no mistakes on PCB and all function is running, I must finalize the discrimination, I am currently on :

RX stage one 4.7nF capacitor and on TX stage one 15nF capacitor. Can someone help me refine these parameters to obtain the initial 20 kHz of the detector.

[homefire]

I will used one TESORO 9'' X 8''

Is that a 20Khz coil?

[bernte_one]

i will see this machine work

[homefire]

WOW! lOOkING gOOd there.

Coming along nice for sure.

[Legaucho]

Hello all

Before the last step, all connections ready now.

[Legaucho]

Very very nice!!!!!
Good work
In my lobo design i found lot of problems with coil, do you plan use a original coil?

Bye Max

I will used one TESORO 9'' X 8''