TESORO GOLDEN SABRE

[ivconic]

Just saw this photo on other thread; justify my doubts about pcb.
Seems they also reconsidered S/N issue and made nice ceramic pcb, smallest as possible to improve ratio....ha,ha,ha...dirty trick!

Usually ground potentials at lowest frequencies presents sort of "sucking antenna" for various interferences. In audio technique is imperative to reduce those at very minimum, cose everything is later pretty audible in speaker. So usually when projecting audio preamps and amps, designer tends to form ground loops at one and only spot on pcb. Many loops will degrade S/N ratio more and more. We can freely observe metal detector as sort of audio device, dealing with very low frequencies. So pcb design is more than important here, among other important things.

[Max]

Hi Max
You are right , but I didn’t have short short circuit on coil.
The faraday shields at the transmitter . And receiver coils open in the region
Of gap .
Please more explain .
Best regards.

Hi,
you must have the gaps and you have but the overlap area covered with al foil is seen as a shorted turn by the MD. In that oval shape you have actually a conductive turn that's coupled with magnetic flux generated by oscillator: this produce strong eddy currents in that shielding , closed, loop that will damage your detection range.

So, put some e.g. tape between the two shields where they touch and you solve that problem.

Kind regards,
Max

[Eugene52]

TESORO GOLDEN SABRE

Hello Ivconic , If it chatters only at maximum sensitivity than it is a very slight circuit problem . And not the pcb board . Is your TGSL case Metal or Plastic ???............I fired and retired the "amtech2005" from this forum !!!! And is now Eugene52........I am now junior Super Tech here Cheers.............Eugene

[ivconic]

Hello Ivconic , If it chatters only at maximum sensitivity than it is a very slight circuit problem . And not the pcb board . Is your TGSL case Metal or Plastic ???............I fired and retired the "amtech2005" from this forum !!!! And is now Eugene52........I am now junior Super Tech here Cheers.............Eugene

Detector enclosures are from plastic. Yet, i keep front panel mostly to be metal. If not, than i usually put another piece of metal plate on inside of panel. If you observe my 1265 pcb, you can see some more Cu area at rear side, planned to hold metal "L" holder for coil jack. Also most shortes possible wires from pcb surface to jack. Ground plane is good and benefitial if used smartly, otherwise it can present "radiating" body in overall design; if to many loops incuded there.

[aft_72005]

Hi,
you must have the gaps and you have but the overlap area covered with al foil is seen as a shorted turn by the MD. In that oval shape you have actually a conductive turn that's coupled with magnetic flux generated by oscillator: this produce strong eddy currents in that shielding , closed, loop that will damage your detection range.

So, put some e.g. tape between the two shields where they touch and you solve that problem.

Kind regards,
Max

Hi Max
It was working well later, I did what you said me , also you and Qiaozhi are right.
Theory is true, but it is strange .not any happen after Banded coils with tape.
Best regards.

[Max]

Hi Max
It was working well later, I did what you said me , also you and Qiaozhi are right.
Theory is true, but it is strange .not any happen after Banded coils with tape.
Best regards.

Hi,
this is the good way of doing it, keep separate the shields of tx and rx coils.

I like this way.

Now, about poor results you have to optimize wiring also: read when Ivconic talk about short leads to e.g. panel socket etc all that is another key factor.

I don't like alligator clips there and that wire, why don't you try something shielded cable instead ?

Also, the CHAIR ! Are you sure the chair has no metal inside like iron rivets or nails ? Cause if so you could get lowered sens from detector too.

So, are all "details"... but are important when searching for optimum.

Kind regards,
Max

[eclipse]

Guys I trashed the damn board! I desoldered almost all valued components and I'm making new board for the TGS. Bolder traces, higher copper thickness, no ground plane..
(it could be the plane doing the nasty stuff around, I think I prefer the chatters for a starter)
--
I also needed some additional stuff (pots, diodes, etc) and had the chance to order few more ICs for testing so soon we will have BATTLES:

1. LF353 (metal can) vs LF353N (ST) vs LT1057 (LT) vs TL082 (TI)
2. LM393 (ST) vs LT1018 (LT)
3. LM308 (motorola) vs LT1008 (LT)
4. LM358 (ST) vs TL082 (TI) vs OPA2277 (BB-TI)

Funny thing is that the LF353 metal can looks old, perhaps 10 years old, taken from old russian TV Elektron
( and they are famous all around with the weight - more than 100 pounds, tons of parts I tell you ..)
Manifacturer logo looks like a triangle, can't recognize it.
We'll see how the Old timer works :P

PS: Check out the avatar I think it's the most appropriate!
Cheers

[Max]

"Manifacturer logo looks like a triangle, can't recognize it."

Like this one ?

Kind regards,
Max

[eclipse]

Hi Max, it's not AD.
Here is a picture of the device, looks old isn't it...?

[Max]

Hi Max, it's not AD.
Here is a picture of the device, looks old isn't it...?

Hi,
yes... it's old... it's a Thomson-CSF's metallic LF353... very old!

http://en.wikipedia.org/wiki/Thomson-CSF

Kind regards,
Max

[Max]

LF353 vs TL072 etc

Hi,
today I tryed again and again to spot the difference between LF353 (used in original design) and TL072...

I made that a number of times so didn't expect anything new... this post just to signal what I think of both.

So far I tested also TL082, TL062, TLC2262, MC33178 and NE5532A at that place.

Start with others... OK TL082 is same of TL072 so read ahead for details. TL062 is not good there, too noise. TLC2262 and MC33178 work somehow... but not that good there.

The NE5532, just forget about, doesn't work any good.

TL072 is good at preamp: I use always during testing and it's good always, same for TL082, are stable, not much noise... and good performance.

So what's the difference between 072 and old LF353 ???

It's more sens with LF353, not much, but more.

Say that can add up to 10% more performances than on TL072, so if e.g. you have 1eur at 30cm with TL072 expect also 33cm with the LF353.

The price is more chatters, sometimes you trigger detection and the LF353 generate more "oscillations" in the output sound that last for a while... on TL072 you'll not see that, if everything right.

That's it.

I'd like to know of other comparision too... with other low noise stuff.

Kind regards,
Max

[ivconic]

Speaking of Thom(p)son...

Max...here is better avatar for you !!!

[Max]

Speaking of Thom(p)son...

Max...here is better avatar for you !!!

Uhm... I like the AK too much...

[eclipse]

Hi,
yes... it's old... it's a Thomson-CSF's metallic LF353... very old!

http://en.wikipedia.org/wiki/Thomson-CSF

Kind regards,
Max

More than 10 years old... few years before I first heard what's a transistor
no wonder I haven't seen this logo before.
I like the weapon avatar mania, Ill stick with the clever cavemen for now

[ivconic]

Hi,
today I tryed again and again to spot the difference between LF353 (used in original design) and TL072...

I made that a number of times so didn't expect anything new... this post just to signal what I think of both.

So far I tested also TL082, TL062, TLC2262, MC33178 and NE5532A at that place.

Start with others... OK TL082 is same of TL072 so read ahead for details. TL062 is not good there, too noise. TLC2262 and MC33178 work somehow... but not that good there.

The NE5532, just forget about, doesn't work any good.

TL072 is good at preamp: I use always during testing and it's good always, same for TL082, are stable, not much noise... and good performance.

So what's the difference between 072 and old LF353 ???

It's more sens with LF353, not much, but more.

Say that can add up to 10% more performances than on TL072, so if e.g. you have 1eur at 30cm with TL072 expect also 33cm with the LF353.

The price is more chatters, sometimes you trigger detection and the LF353 generate more "oscillations" in the output sound that last for a while... on TL072 you'll not see that, if everything right.

That's it.

I'd like to know of other comparision too... with other low noise stuff.

Kind regards,
Max

Yes i have almost the same experiences.
Usually i put TL082 when not having LF353, works just fine there. NE5532 is just not working at present setup. I think it will work just fine too, if we readjust components arround it. TL072 is actually TL082 so..same story - it can be used there pretty successfully.
Recently i got LS204 in metalic case. Not tested yet, but i will test those for sure.
It is not a big deal to replace and readjust front end at TGSL.
What bugs me more are LM308 and LM393. OK..TL081 also tested instead LM308 and to tell you the truth; those really do the job with less noise.
But LM393 is a real pain in the .......coil!!!
I am sure that TLC2262 can replace those, even work better, but i simply cant find those in local shops!
Or even better TLV2262.

Another thing...LM358 could be replaced with something better, but which one? I was thinking to put there 4 x opamp instead 2x LM358.
Is it good idea?
I am planing to redraw pcb for that matters soon.
What should i consider to put there? TL074,TL084? LM324? LF444?
So far i used mainly LM324 in many circuits and those suits all the demands.

I am quite unexperienced refering some specific questions, so i will freely ask here, please dont laugh;
are there any changes (benefits,drawbacks) if two double op-amps are replaced with one 4xop-amp? Refering hums,power drains, signal paths etc.etc...?
Reasons why am i asking this funny question is more than naive..but hey, i want to learn and be sure.
Theoretically it should be the same thing; 2x double or 1xquadro...same thing.
But in practice i noticed some thing; usually those cheap chinesse detectors DO have quadros more than singles? Why? Production costs?
Other hand, branded machines usually do have plenty of "doubles" and rarelly some "quadro"....
Ok...many branded's do have TL074, 27m9, LF444 and similars... and also more "doubles" but my (weird) statistics is pushing me to start thinking on this as some special reason.
I havent seen any 27mxx or LF... on chinesse toys, but mostly LM324's and TL064's. Again, on branded machines usually are mentioned and very rare "quadros" like TL064 and LM324..?
Is this only my imagination or there is something else there?