Tesoro Lobo news

[ZOUjiarui]

Oh, and the schematic for the above post is 7808. lm2930 is hard to find

[LukaZ]

I would like to know if there is anyone who managed to complete Lobo successfully.

here it is. it works fine on the table;
https://imgur.io/a/AdWVphh

[Maurizio2]

Please, can you publish the schematic revised correctly?

[LukaZ]

it was done according to this diagram, my Lobo works at 17.5kHz, C14=250pf, the RX coil should be set to 18.1kHz, I haven't done that yet, and I still need to check exactly. IC, U4B, in parallel with C9, instead of a 100K resistor, a 500K trimpot should be placed, also, on Lm392 responsible for battery monitoring, instead of 3k3, a trimpot for fine-tuning the threshold is placed. I used a probe from a Golden Mask, and it is very close to the inductance of a tesoro probe, for a device at 17.5kHz

edit: I also had to remove R5, for some reason with it, IC7660 wouldn't work

[LukaZ]

the easiest way is to get this pcb, and if it is identical to mine, you need to make two simple changes on the back, and the enjoyment can begin.

[Malospelos]

Good morning friends, yesterday I finished assembling the PCB mentioned above with a Tesoro Tejon Widescan 12x10 coil, it works well but I only get 25cm on a coin at most, I have that PCB, what modification should I make? What depths do you get with this unit? ?
I have the frequency at approximately 17.2, and it is sensitive to small objects, the ferrite cancels out and discriminates in its range, in principle it is fine, the only thing is that the depth is a little poor.
With TGSL I get almost double the depth with the Ultimate coil

[hossein62]

My Lobo is working, but there is a problem with the coil (Tx - 170 coil wire 0.2 - 47n, Rx - 65 turns with wire 0,3 - 6n8, 25 x 12.5) - can not see well in the "all metal", the "discrimination" is much better, but after adjustment potentiometer on the 30% no longer sees metals (R10 - 100K). By moving relative to each coil, I noticed that at some point the speaker is silent, and here begins widzić metals. In the most optimal point on the oscilloscope is a graph as in this picture of "my lobo" (measuring points at the exit to the coil). With a genuine Lobo noticed that the chart here is a little different (photo of "original lobo" - the second sine wave is almost flat despite the same oscilloscope settings). When I try to get a graph similar to the original in my lobo stops working properly (adjustable potentiometers on the board also does nothing). My question is whether it can change the number of turns in the coils? Thank you for all the answers.
1. My Lobo
[ATTACH]25623[/ATTACH]

/ 2.Oryginal Lobo
[ATTACH]25624[/ATTACH]

thanks for very nice photo .

the RX voltage of orginal lobo have +90 degree phase with TX voltage!!

[hossein62]

How,
If anyone is considering building the Lobo-Lite, then there is one thing that needs consideration. The sensitivity circuit needs a little work, I ran out of time and didn't fix it.
As the circuit is above the maximum sensitivity is when the pot is at about 75%. It appears that full sensitivity swamps downstream circuits. The 2k2 before the sensitivity pot needs to be increased a bit more....how much? I'm not sure and don't have the time to check....I just make sure I don't turn my pot on more than three quarters.

Here are a few air tests, target weights in grams. The 5" round would probably get a 0.02 or 0.03 at a similar distance to the 0.08 crystalline piece, I didn't have anything smaller handy to test with. (Note also an obvious mistake (sorry) on the graphs the smallest one is 0.08 grams and not 0.

This machine will see many if the flat nuggets on edge at very respectable distances too, much better than a PI, this is exactly what you want for a bedrock sniffer where many of the pieces will be sitting vertically in the cracks and crevices.

Cheers
Kev.

hello Kev.
thanks for share very useful information.
What was the material of the nugets you used for testing?
Because with a homemade coil, I was able to detect a piece weighing less than 0.03 grams in all metal mode at a distance of 6 cm for air test, but it was not very sensitive to non-ferrous metals!!
That's why it is very important for me, what was the type of metal with which you did the test?

[Kev]

Hi hossein62,
If you look at the bottom of the post #212 you will see an image of the targets I used, that Carl has so kindly preserved all these years. All native gold running about 95 to 96% pure.

Note that I wrote 0.8 on the graphs when it should've been 0.08 or 80 milligrams.

Well done making your own coil seems like a winner. Making the coil to suit your machine or adjusting the front end to match your coil gets rid of all the compromises the manufacturers install for mass production, really making a hot combo!

Cheers
Kev.

[hossein62]

Hi hossein62,
If you look at the bottom of the post #212 you will see an image of the targets I used, that Carl has so kindly preserved all these years. All native gold running about 95 to 96% pure.

Note that I wrote 0.8 on the graphs when it should've been 0.08 or 80 milligrams.

Well done making your own coil seems like a winner. Making the coil to suit your machine or adjusting the front end to match your coil gets rid of all the compromises the manufacturers install for mass production, really making a hot combo!

Cheers
Kev.

Hello Kev.
Thanks for the answer.
Yes, I was hurry and I forgot to see the third photo.
The photo you posted helped me a lot. As a result, I realized how much I should expect from Lobo.

I made several coils, 2 of which are 5x10 DD and the 3 of 5 and 6 inch concentric.
I did all the tests with in All Metal mode.
Concentric coils are more sensitive than DD coils. But their problem is that they are not well balanced. For example, the output voltage of the receiver part does not fall below 1.5 volts when the sens is maximum, but for the DD coil, it was easily reduced to 100 millivolts.

So for concentric coils I have to set the SENS to half or less for the threshold sound to appear!!

I would totally welcome any ideas that would make the concentric coils balanced

coil3_6inch was the most sensitive. A small piece that is in the attached pictures from distance 5.5 to 6 cm detected by SENS on less than half!!
but I don't know how much it weighs and whether this amount of sensitivity is good or bad!!


coil4_5inch detected the same piece at 4.5-5cm with SENS on about a quarter.

The coils have a phase problem because I used 4558 instead of ls204 and I think the phase of the receiver is different from the original one and unfortunately I don't have a 2-channel oscilloscope to measure the phase!!

You don't have to worry about using commercial coils . if you give me the coil specifications
TX_inductance = ?
TX_rs = ?

RX_inductance = ?
RX_rs = ?

Phase =?
frequency = ?


I can calculate the amount of capacitor and coil gain for an arbitrary phase for lobo.

[LukaZ]

instead of LS204, I used TL062, and it works fine, I was not satisfied with 4558, most likely due to phase problem.

[hossein62]

instead of LS204, I used TL062, and it works fine, I was not satisfied with 4558, most likely due to phase problem.

hi lukaz.
TL062 is often used instead of LF442 !!!
i use Ts512 instead of ls204 . its very good.
Ts512 is shown in (ST electronic)datasheet LS204as an alternative.

[Boadil]

the easiest way is to get this pcb, and if it is identical to mine, you need to make two simple changes on the back, and the enjoyment can begin.

Could you post photos of these modifications? I have everything set up and I have questions about this modification and the capacitors to use to have one working frequency or another?
I have the same board assembled as you.

[LukaZ]

I can, why not., but in about five to seven days, when I have access to my pc, because now I'm roaming., until then, I'm interested, did your device work?, I guess it didn't, because, in my case, the connection was missing, if I remember correctly, in the part of the input stage, and one branch of the power supply was missing, I forgot exactly which one on which IC., also, it would be interesting to see a picture of your board from both sides, if there is a possibility for it.

[pechkata]

Hello, it doesn't work properly for me.
There is a sound from the general background.