TESORO GOLDEN SABRE

[Geo]

Hi Max.
All Fets are BF245C. I hear the 480Hz and i see on scope and i measure it with Freq counter. A lot of instruments for nothing. Now i will go again at the lab to give it again a try. The only that i dont connected right is the 10uF tantalium. I have not it so i connected a 4u7. I think that it is not the problem.
I will write you later, now i go to the Lab (it is down the stairs)
Regards

[Max]

Hi all.
I am the same with you. I made the GoldenSabre. Of course it don't work. Why........ i don't know, i am very tired to check it. I connected it only as "all metal" mode because i had not the time to connect all the potentiometers and the swiches. So all metal..........one pot for sensitivity and one bridge for the all metal/disc mode and it was ok. But what OK if it dont work. I connected a coil that i had from CL3 and i have a very good oscillation at 15.5Khz. The sine is perfect, the voltages are +8v and -6.2v. When i put an object near the coil i see a variable at the output of LF353 and from LM358 and LM308 but not at the last LM358. The MPSA13 give a continuous tone of 480Hz tone. I take out the last 358 but the MPSA sounds yet. I look with the scope to the colector of the MPSA and i see a sine wave about 10Vp-p. Who is the job of the 220uF capacitor??? why it does not decouple the AF signal?????.
Maybe later or tomorrow to check it again.
Bye

Hi,
which fets have you used ? BF245 ? if so no problems ... but if you use BF244 or different ones check your pinout cause there are very different from model to model and also from one manifacturer to another.

The fact you ear always the 480HZ tone at output or read it by scope means that maybe the battery checker fet doesn't open (again look at pinout) when capacitor charge.

Check that and let us know.

Kind regards,
Max

[Geo]

Why

Hi all.
I am the same with you. I made the GoldenSabre. Of course it don't work. Why........ i don't know, i am very tired to check it. I connected it only as "all metal" mode because i had not the time to connect all the potentiometers and the swiches. So all metal..........one pot for sensitivity and one bridge for the all metal/disc mode and it was ok. But what OK if it dont work. I connected a coil that i had from CL3 and i have a very good oscillation at 15.5Khz. The sine is perfect, the voltages are +8v and -6.2v. When i put an object near the coil i see a variable at the output of LF353 and from LM358 and LM308 but not at the last LM358. The MPSA13 give a continuous tone of 480Hz tone. I take out the last 358 but the MPSA sounds yet. I look with the scope to the colector of the MPSA and i see a sine wave about 10Vp-p. Who is the job of the 220uF capacitor??? why it does not decouple the AF signal?????.
Maybe later or tomorrow to check it again.
Bye

[Max]

I've just fixed the dodgey wiring in the plug of my 10" Tesoro concentric coil. The residual voltage is 4mVpp.

So far I have measured:
9x8 web coil = 13mVpp
Laser 8" concentric = 100mVpp
10" concentric = 4mVpp

All of them work fine on my detector, but the one I prefer is the 9x9 web coil. It gives a crisper sound. Probably because of the 60mm receive coil.

Hi,
yes sound is good but the conic shaped flux that's so cool when you pinpoint targets is also cause of lost of many targets if you don't sweep it at low advancement (5-6cm) ahead each time... too close for my taste... that will require days to scan even a small area.

The good recipe is making a 120+120turns 30AWG DD22 coil... that has more performance and doesn't lack too much about pinpointing...and you don't lose targets at same depth you can find with 9x8''.

If you need a nice coil for coins or other small things... to be used on bandido or other uMax make one... null at max 1mVpp and it will be rock solid and better than 9x8''.

Kind regards,
Max

[Qiaozhi]

I've just fixed the dodgey wiring in the plug of my 10" Tesoro concentric coil. The residual voltage is 4mVpp.

So far I have measured:
9x8 web coil = 13mVpp
Laser 8" concentric = 100mVpp
10" concentric = 4mVpp

All of them work fine on my detector, but the one I prefer is the 9x9 web coil. It gives a crisper sound. Probably because of the 60mm receive coil.

[ivconic]

Since i havent started yet to learn how to use it, is not too late to switch on LTSpice ! Thanks a lot Porkluvr! I'll install it and try!

Now, these are simple schematics; milivoltmeter i made and it is working very good. Although scale i do have is low resolution so error can occur. Need high resolution scale to run it just fine. Another, smaller schematic i took from some musician site. It is absolute miracle how this small,tiny preamp working FANTASTIC on guitar pickups!!!!? So those are coils too, arent they? I was thinking to experiment with this preamp a bit more....Seems nice to put it as RX front end...

[porkluvr]

I have Tina 7 TI installed in my system. Actually i just installed it, few days ago. Still novice in this thing. What do you think? Is it good for a start?
Regards!

I've played with TINA. Much too restrictive. Please, do not waste your time. TI makes good ICs, but their TINA addition is a second rate answer to LTspice. Please believe me.
Download LTspice, and forget about using TINA except for evaluating (ONLY) TI products.
TINA might be better suited for noise analysis than LTspice, but so far as I know, you can only evaluate TI products with the TI version of TINA.
I tried TINA's "evaluation version", several times (years ago, they MAY have changed) and it did absolutely NOTHING for me. (Actually, I may have just been too stupid to get it to work, but that was THEN, and this is NOW.... hmmmmmm. I won't do it again, and again, and, but, I tried several times.)
That was, oh, about 3-5 years ago. TINA may be different now, but... .. Hmmmmm if someone were to ask me what to do.... I would have to say:
I remember that I wasted time trying to get TINA evaluation version to work. I REMEMBER. SWITCHERCAD, on the other hand, was straight-forward from the beginning. Then it morphed into LTspice and it got even better.
So, I recommend:
Download Ltspice.
Run it.
Use it.
You won't be sorry.
You can run TLC2262 with LTspice. So, by the same token: try to run LT1037, or LTC1046, or MC33178 with TINA? (Gag-choke; not allowed, I'll bet)!!! DOES THAT SEEM FAIR ? Damn right it doesn't.

Love those TLC2262, but if you can do without noise analysis, RUN WITH LTSPICE!

[ivconic]

I have Tina 7 TI installed in my system. Actually i just installed it, few days ago. Still novice in this thing. What do you think? Is it good for a start?
Regards!

[porkluvr]

not the answer

Geo, the FET circuit will fight (and defeat) you when you try to exceed the "design limit". Ten volts is about all I would suggest using. Changing to a 10V supply requires changing the feedback components (use 2N4392?) - or else removing them.

From my experience: a different approach should be used to gain appreciably more power output. Remember, we should operate the phase reference circuits at approximately 50-50 duty cycle.

In my opinion, this particular circuit can not be forced to deliver much more power - or else it will cause unacceptable non-symmetry of the transmitted wave and (especially) the phase reference voltage. How accurate would discrimination be, if it was fed a 55-45 waveform?? I don't enen like to see a 51-49 waveform!! (Well, that's just my problem. Not everybody needs to be a perfectionist.)

I can supply you some of my spice simulation circuits if you would like to experiment with LTspice (it's free). Some people would disagree, but I think it's pretty easy to use. Sometimes, it's almost likeable. It's up to you. Send a pm if interested.

I would like to have a real-life laboratory, but I still live in a shoe where there's not enough room available. temporarily............................... ........... ............. (time keeps marching on, and on, and on.... )

[Geo]

No Geo! Beware! I sad that made MISTAKE considering pin 1. under notch...
It is pin 8. under notch not pin1. !
Yes there are 4k7 resistors in chopper, not 47k as showed in schematic.
There is also 2k2 instead 33k....
about 470k in battery test....i put 470k,it is working...
1M resistor goes parallel to diode...only if you want to boost audio. For now do not put it.Leave as it is...

Ok Ivconic.
In the schematic there is a diode at one LM308 that there is not on the pcb (pcb shows only one LM308 with diode parallel to the feedback resistor). Do you connected it??
I finished the pcb with the components. Now i must connect the potentiometers and switches and it is OK. Maybe tomorrow .... today i am busy.
Regards

[Geo]

Hi Porkluvr. Can you simulate the circuit with Tx transistor the 2N2219 and Vosc=18V. I want to see how much bigger will be the Tx signal and if the signal phase is the same.
Regards

[ivconic]

Thanks Porkluvr! I have good will to experiment more on this...

[porkluvr]

too much Q?

Ivconic-
False targets could be caused by instability of the DISC opamp.
The high value of feedback along with input capacitance can cause ringing.
It will be worse if you have a Hi-Q coil.

I had a longer spiel typed up to explain my screen shot image,
but my computer crashed while editing the photo. I hadn't saved the text. Sooo, I'll just post the before and after photo and let you determine if you can use the info.

Adding a capacitor across the 100k resistor makes the TGS DISC control similar to the Bandito's topology.

[Max]

I do have idea already....
Glad to see that you suggested scale...only have to find good one.
I'll prepare schematic of "coil balancer" and post here later...
Actuallly i dont need to include separate oscillator!?
Best way is to suite exact coil to exact device and only way to do so is to use origin oscillator from device, when balancing coil...
So i'll consider only RX part...

Regards!

Hi,
yes you could add a general purpose oscillator... with variable freq. from e.g. 1KHz to 20KHz and variable amplitude of 1Vpp to e.g. 10Vpp... I think the easy and best thing could be :
- a bf oscillator Wien type
- some ic like ICL8038

+ some power stage (class A transistor amplifier)

That way you have really good shaped sinus and stable frequency on the BF region... and also really few distortion from end stage.

Maybe the ICL8038 could drive coil directly... using some small impedance matching component... so saving also the work to make output stage.... or one could use also some old small function generator to do the same... maybe just dismantling board and enclose everything in a single box (osc+meter stuff).

The advantage of using an old signal generator (like e.g. some 70's HP I have in mind) is that you could also pump a sweeped signal to trace self resonance of coil... by meter !

But it will become more complex of course.

Best regards,
Max

[Max]

I attach here the pcb with errors that Max sent here. I have checkthe 10pF... the 1M and one diode that there is at the schematic but no at the pcb. Tell me if are correct.
I have 2 LM308 with metallic case. Where is the ledge??? Ivconic said that it is on pin1......... i looked at datasheet and shows it at pin8. Who is the right.... the shop had only 2 pieces so i dont like to burn it.
Regards

Hi Geo,
look at green oval... there is the diode (labeled as D12 in TGSL schematic by Ivconic) : you have to put the 1M resistor there in parallel to diode... but using the switch in series... to connect/disconnect it.

Be aware of it if you notice too erratic noise without. If there isn't too much internal noise you can use it gaining better audio for far targets and weak signals.

About the cap... yes... 5 or 10pF. You can use 5pF without problems; circuit works also with 10pF there... me cannot see or ear differences by that.

Looking at other schematics by Tesoro now actually I think it was 5pF and not 10pF. But maybe TGS is different from them... who knows.

Important is that works with both.

Best regards,
Max