Tesoro Lobo news

[Fabian]

Doubt

Hello everyone. I was checking one of the FOMA diagrams, and I was struck by the position of the FET's: Are they inverted the source and drain legs?
At least I understand that according to the diagram signed by WL of 6/90 and looking at the pictures of the original PBC ...

Could someone with more knowledge take a look?

Thank you,

Fabian

[Derx]

my modified lobo 100% working with coil balance up to 500 mV

measured in input j-fets

[Derx]

you are coil balance is out
re-balance coil, or drop it to recycle

original sheet lobo is lame horse because of this scheme, you can squeeze more
because it is designed beginners-suckers

[ZL17]

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


/ 2.Oryginal Lobo

[Davor]

Glad to hear that. I noticed some odd capacitor values, but didn't bother much with them as I did not build this rig. I might build a lite version if time allows.
Anyway, for the sound quality, play with diodes at U2. You may extract a diode coming from pin 5.

[ZL17]

Davor Thank you for your response. After many attempts is better. The C7 - 10p treshold has not worked. I changed the 10N and operate. Then swapped C14 (250p) at 560p - that only had (originally in Lobo 510p + / - 5%). But there is a little problem: the limit of audibility is annoying throbbing sound. Can anything be done to make the sound more smooth (as to increase its frequency?). I have to add that I am using oryginelnej coil Tesoro Lobo, on the oscilloscope I have some problems because I have a faulty probe. Discrimination is very poor but it works (R10 - 100K). The NE555 to R4 (15K) added in parallel (trial and error) 47K and so I picked up the frequency. After the change range (maximum sensitivity) is almost the same as in the original Lobo.

[Davor]

You can start by tuning your Tx for maximum amplitude. Adjust a scope for 100V on a working input, and tune the frequency on 555 for resonance. To do that adjust VR1 for some small amplitude on Tx coil connection (with coil connected, of course), and find a maximum amplitude with VR2. You might need to reduce amplitude with VR1 again when you are close to resonance, Once you find the resonance increase the amplitude till the maximum and a little bit more. You should get about 16Vpp at Tx coil.

Then tell us the difference.

[ZL17]

I borrowed from a friend oscilloscope (it has two channels but only one probe) so I'll check on that though well I do not know - what points should be checked oscilloscope to properly tune the coil? I also have a question: which is the responsibility potentiometers on the PCB (except treshold). Is the C14 should be 250p or 510p (I noticed that the more sensitive is the 510p). Thanks for any answers!

[Davor]

7555 is a CMOS version of a NE555. Because Lobo uses discharge pin 7 to drive a PNP, I don't expect much difference in driving capability between these two, but because it uses pin 3 to make it oscillate, the CMOS version should have superior symmetry. Again, it would not make much influence until you hit the noise floor. At 5cm you don't.
I believe your 555 is not tuned well. It provides frequency drive for a coil, and Tx coil is supposed to run near resonance. Most probably you'll need to tweak 555 frequency to hit the Tx resonance. Do you have something to measure amplitude of 20Vpp?
I also believe a capacitor parallel to Rx coil should be omitted. It is supposed to improve noise performance, but it provides only a negligible gain with considerable coil loading. If omitted nothing cardinal happens, only the rig becomes less touchy.

[ZL17]

I would add that I have NE555 instead of 7555 but I think it does not matter. Please help me.

[ZL17]

Colleagues, help me, please. I built Lobo was a problem - poor sensitivity. Building your detector had available to original Tesoro Lobo. In my unit, I used the original coil Lobo. My detector sees coins (on discrimination) to 5 cm, and the ALL METAL does not work. Even built a coil that sees the coins in my detector, also at a distance of 5 cm. In my Lobo integrated circuits and transistors are the same as in the original - the only thing that is different is I instead of 39.3 ohms 38.3 ohms. How do I increase the sensitivity of the device? What to look for? Thank you for all the answers!

[Fabian]

Hello 6666. I sensed that the sentence had not been clear, sorry.
In the archive there are two schemes, one of them has build explanations for the coil. That's it.

Shevakotik: Hello. How is your project? It looks perfect with a two-sided homemade PCB with a very good finish.Congratulations! Tell me: Does It Work? Could you make the coil? Tell us a little about that. (And maybe you could help us a bit with the Russian language )

Regards,

Fabian

[6666]

Fabian
can you please tell us what the words say about the coil information on the schematic , thanks

[shevakotik]

[Fabian]

FOMA PCB

Hello everyone. I leave here I could find so far. I think it is the same information used by Legaucho for your project. It's all about Foma PCB version and another slightly changed by me, the version called OK (I only played tetris) According Foma, the scheme in which NO leaves the coil works when building exactly as in the diagram. Apparently, he achieved a better performance by changing some values, but I can not say what they are.
As for the coils, the specifications are those in the second scheme and I believe are good.
I'll try to build it with these specifications as done with my other projects, because in the summer (winter for most of you) want to go for gold in a river I know, and this is the only project around here that serves for that, but first I have to finish my second Bara and the first White's IDX (fighting with coils ...)

Best Regards

Fabian