lobo improved

[Legaucho]

Lobo

I have finished the PCB for Lobo with Sprint-layout. I would like that some one can check it. Sorry for my english language but I' try it
Thank by advance.

[Legaucho]

Help

No one want to check my job, please take a look on it. I want to be sure before to make PCB.
Thanks

[porkluvr]

No one want to check my job....

Maybe it's because there has not really been a concensus on what is the correct circuit? I wouldn't know what your board is supposed to look like because I don't know which schematic you are going by. There have been several versions floated here, and not 100% agreement on what works. best.

There probably will never be 100% agreement, but which schematic should your PCB be checked by?

[Legaucho]

Maybe it's because there has not really been a concensus on what is the correct circuit? I wouldn't know what your board is supposed to look like because I don't know which schematic you are going by. There have been several versions floated here, and not 100% agreement on what works. best.

There probably will never be 100% agreement, but which schematic should your PCB be checked by?

Thanks for your answer,
I work with two schematic, one is -LOBO- 10-3-89 and the second one is TESORO LOBO W.L 6/90 I have also the shematic from Foma ( with notes of you). A question is now witch one is very close to the original !!!!

We need some numeric pictures from the Original Tesoro Super traq PCB.

[porkluvr]

I'll take some time and do a check for you - tomorrow. I've been kind of busy today. It seems a lot like work, but I have some spare time. And, since I am working on constructing a sort of LOBO detector (on again-off again that's how I "work") I just might learn something.

Later

[Legaucho]

I'll take some time and do a check for you - tomorrow. I've been kind of busy today. It seems a lot like work, but I have some spare time. And, since I am working on constructing a sort of LOBO detector (on again-off again that's how I "work") I just might learn something.

Later

Many thanks, I'll wait for your conclusion..

[tchoci]

Lobo is a very good detektor.Otkakto did test it regularly in real usloviya.Imam very good results.

Tchoci!

[porkluvr]

Tchoci, do you have measurement for your RX coil inductance? I think I can go back through earlier posts, get coil dimensions and then use that data to calculate inductance, but that method is very inaccurate.

Even a relatively small amount of change in coil value would affect receiver phase, so any more information will be greatly appreciated.

Forgive me if you have already stated this. I saw transmit inductance but I can't find it for your rx coil.

Thank you.

Almost forgot- I am looking over the schematic where you marked 2x2.2nF (4.4 total) for the rx capacitor but I read an earlier post where you said 1.3nF. Which one is correct?

[FOMA]

C5-very important capacitor, it is necessary to select with each sensor.

[porkluvr]

Thanks, Foma. Most of the schematics posted so far have had some IMPORTANT information missing, or else did not agree. Maybe it's because of lack on commonality in the coils - different coils requiring different capacitors.
The first schematic I saw was totally lacking probe information. There have been several diffent versions seen here so it's hard to know which one is best.

Your schematic is very complete, you have information for both the TX and the RX coil sections. But I just noticed that you are showing 17500 for the TX frequency. I am confused because Lobo is supposed to operate at 20k. SuperTraq works at 17.8. There is no mineralization control, so this cannot be a supertraq.

Another problem I see is that if the TX coil and capacitor are 1.33mH and 47nF (.047uF) then the natural resonant frequency for the tank circuit is about 20000. So instead of giving good information this is just adding confusion.

Another thing: I might be wrong but I do not believe that the component values shown will allow the 555 to output 17500 (except at the very end of the frequency trimpot's travel). So, what is going on here? I don't think you are intentionally giving bad information, but this is not what I am looking for.

[porkluvr]

correction

I think Math's fun. I'm not real good with it, but it's fun.

[FOMA]

VR2=0, R4=14k7 C1=2H2 under such parameter F=17500HZ
Ñ1 I did not change.
But who has measured the persisting frequency LOBO?

[porkluvr]

VR2=0, R4=14k7 C1=2H2 under such parameter F=17500HZ
Ñ1 I did not change.
But who has measured the persisting frequency LOBO?

Why would you chose the operating frequency at 0% pot travel?
What is meant by Ñ1? I do not see it on the drawing.

I am not an authority, but here is my logic: When an engineer designs a circuit that requires potentiometers for frequency setup, he will select component values with the goal of making the target frequency easy to attain. Preferably, that target frequency will occur with the potentiometer somewhere near its center of adjustment range. It would be a poorly engineered product if it was needed to turn the potentiometer all the way to one end or the other to attain the correct frequency.

Here is a link to the LOBO manual: http://www.tesoro.com/info/manuals/older/lobo/
20khz is listed as the approximate operating frequency.

When I setup a LOBO simulation with the component values shown in our "faked" schematics, I obtain 20kHz operating frequency with my virtual potentiometer turned to about 45~55%, depending on which way it is facing. (Ah-HAH! That was good Tesoro engineering!)

You show that 17500 is your operating frequency, which would be OK except that it can only be obtained with the frequency selection potentiometer turned all the way to 0%.
And, (assuming that 47H is .047 microfarads, correct?) according to the tank circuit components on your schematic, 20kHz would your approximate operating frequency. That's from basic electronics math. You say 17500, but the component values say 20000. I think those two numbers are not very close.

Soooo, you are either driving the coil circuit off resonance or else, more likely, your tank circuit components are not as shown on the schematic. You give confusing information.

Because correct phase reference and demodulation setup depends on having correct operating frequency, I cannot know what to do from following your drawing because 17500 and 20000 do not match.

[FOMA]

I read Tesoro com. No need this believes.
Frequency Tesoro Gold(en) Sabre there 12 Khz
But indeed 15kHz.

[simonbaker]

We need someone with actual Lobo to put oscilloscope probe near search coil and measure actual frequency. But make sure very clear which model (version) it is!

Cheers,

-SB