Tesoro Lobo news

[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

[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

[Derx]

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

measured in input j-fets

[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

[ZL17]

I solved the problem! Through the alignment of the coils got close to the original graph. Additionally did shielding coil Tx and strengthened the resin. Discrimination is ok but the problem is the setting of the signal lead. When using headphones is good but after disconnecting headphones and turn the discrimination is sometimes throbbing sound - what could cause this?

[Davor]

Insufficient power filtering. Try low impedance/ low ESR elcos.

[technos]

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 ...

The drain and source to jfets are often interchangeable;
http://en.wikipedia.org/wiki/JFET#Schematic_symbols

But the ultimate arbitrator to this (and any part) is the datasheet for the 2N4393, and at least on one it is;
http://www.soiseek.com/CALOGIC/2N4393/

So if you note the handwritten schematic has the drain hooked up to the output of opamp, which may seem backwards but in this case does not matter.

But this is one of those niggly things that can go wrong if for some reason the FET is not symmetrical in manufacturer and the builder/designer does not pay attention. But as the wikipedia article noted, that should be reflected in the schematic (like it is hand drawn here). However the CAD drawn symbol on the schematic on the left shows the current flow moving from source to drain from that opamp, with the arrow of the gate near the source. Which means that the schematic indicates source and drain are not interchangeable. (The wikipedia article probably needs to be edited to explain this a bit better). However, the datasheet does say that drain and source can be switched;

http://www.nxp.com/products/rf/transistors/mosfet/jfets/n_channel_junction_field_effect_transistors_for_ge neral_rf_applications/BF245C.html

It appears that the fet is in the same configuration as the handwritten schematic, so technically the CAD drawing on the right used the wrong symbol (as the gate arrow is near the source indicating there is a difference), and the symbol with the arrow equidistant between drain and source should have been used as in the pdf datasheet for the BF245C shows above. But this is a technical drawing error, as both schematics will be functional either way!

The reason why this may be convenient has to do with component placement on circuit boards. It may (occasionally) be advantageous to have shorter traces with high frequency radio circuits (and then you have a better performing circuit). Or have traces that don't have to navigate around the part, when it really does not matter. And this is important when you want to avoid multilayer boards and stay with a double or even single sided board. Even though it may seem like that you are only saving $.02 - multiply that by 1000000 units, that represents $20,000 which could represent someone's salary!

Hope this clears up the confusion just a bit!

[Fabian]

The drain and source to jfets are often interchangeable;
http://en.wikipedia.org/wiki/JFET#Schematic_symbols

But the ultimate arbitrator to this (and any part) is the datasheet for the 2N4393, and at least on one it is;
http://www.soiseek.com/CALOGIC/2N4393/

So if you note the handwritten schematic has the drain hooked up to the output of opamp, which may seem backwards but in this case does not matter.

But this is one of those niggly things that can go wrong if for some reason the FET is not symmetrical in manufacturer and the builder/designer does not pay attention. But as the wikipedia article noted, that should be reflected in the schematic (like it is hand drawn here). However the CAD drawn symbol on the schematic on the left shows the current flow moving from source to drain from that opamp, with the arrow of the gate near the source. Which means that the schematic indicates source and drain are not interchangeable. (The wikipedia article probably needs to be edited to explain this a bit better). However, the datasheet does say that drain and source can be switched;

http://www.nxp.com/products/rf/transistors/mosfet/jfets/n_channel_junction_field_effect_transistors_for_ge neral_rf_applications/BF245C.html

It appears that the fet is in the same configuration as the handwritten schematic, so technically the CAD drawing on the right used the wrong symbol (as the gate arrow is near the source indicating there is a difference), and the symbol with the arrow equidistant between drain and source should have been used as in the pdf datasheet for the BF245C shows above. But this is a technical drawing error, as both schematics will be functional either way!

The reason why this may be convenient has to do with component placement on circuit boards. It may (occasionally) be advantageous to have shorter traces with high frequency radio circuits (and then you have a better performing circuit). Or have traces that don't have to navigate around the part, when it really does not matter. And this is important when you want to avoid multilayer boards and stay with a double or even single sided board. Even though it may seem like that you are only saving $.02 - multiply that by 1000000 units, that represents $20,000 which could represent someone's salary!

Hope this clears up the confusion just a bit!

More than clear! Sorry, Technos, for making use of your time for my ignorance on such a large (and very clear) explanation. The data sheets that I have not made it clear this point (or maybe I did not know understand), which is surely known to every beginning student of electronics.

Thanking you once again, I salute you from the south,

Fabian

[ZL17]

Well, the problem with the pulsating sound of the discrimination resolved. The problem was not connected to the shield wire probe. When connected to the negative all is well. I still have a problem with the fact that I can not set the sound of the lead. Maybe someone knows what the problem might be?

[Fabian]

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

measured in input j-fets

Hi Derx. Could you post the details and some photos of your project? Seems to be one of the few that work around here ...

Fabián

[ZL17]

Do Lobo is a diagram zener diode?

[daverave]

are the diagrams on this page the supertrac version...also ive decided to buy a second hand lobo and i want to know the coil inductances so i can make my own coil...also can a 5 pin tesoro coil be modified to be used on a lobo.

[ZL17]

Hello colleagues! I'm not an electronics away excuse for the content of the questions. I have a few questions. I did a coil DD: 1.33 mH (, DNE 0.28 mm, about 9 ohms!?) And 10.97 mH (DNE 0.22 mm, about 38 ohms!?) - 25 cm x 13 cm. Do you want to set Tx frequency of 17.5 kHz (measured miltimetrem) or 20 kHz (+ 47n capacitor)? Is it possible to measure the frequency multimeter Rx work? I think that electronics have made good, but the maximum setting "threshold" window there is no sound - whether this is due to the fact that the coil is badly aligned or the problem is with the LM308N (I used LM308N - probably stutter Asian fake, but I changed it to NE5534P the treshold worked well but was poor sensitivity of the coil. LM308AN original already ordered and waiting for delivery). Please help me.

[kt315]

LM308AN original already ordered and waiting for delivery

it is not something warm sound from older lamp amplifier. why you so sharply need to use obsolete components? that is unfathomably for me. there are modern components with better data you can find at low price around. WITHOUT PROBLEM.

WHY do not come back to your old school girlfriend NOW, Buddy? she seems so sweety now!

[djjmilan]

Lobo works on original tesoro12x10 DD coil 17.5khz but also works to 20kHz. 1E 30 cm very good stable but not very good discrimination lobo obscure as much depth. I have more work to do on it yet. But the depth is great.