TESORO GOLDEN SABRE

[ApBerg]

LF353-1

Max:
Hi Ap,
thanks for the good qualiry pictures. Last 4 are like what I have... but I haven't a sinus at pin1 of LF353. Are you sure you are sampling at pin1 ? I'm referring to the original schematic... as in the picture under the red circle

Hello Max.

The signal is from 353-1 it is however not 2 v p/p, but 2 volts per division...
The signals are from the goldy, not from the GS with notch.

Ap

[Max]

Max:
Hi Ap,
thanks for the good qualiry pictures. Last 4 are like what I have... but I haven't a sinus at pin1 of LF353. Are you sure you are sampling at pin1 ? I'm referring to the original schematic... as in the picture under the red circle

Hello Max.

The signal is from 353-1 it is however not 2 v p/p, but 2 volts per division...
The signals are from the goldy, not from the GS with notch.

Ap

Hi Ap,
thanks for the info.

So I have a problem on disc ! Maybe is similar to Ivconic's problem ... the capacitor !

I have just graphite pots... not wire wound so think the problem could be at capacitor.

Thanks again,
Max

[ivconic]

Geo, welcome to the club! I knew you'll make it!

Max, see picture bellow; that was mother ....capacitor!!!

Nothing much to explain; i traced signal from oscillator and noticed nice shape before capacitor and quite deformed after it... When replaced signal had much better shape. When tested on coins and other items...great work!
Yes i am gonna add notch "substitution" today to see differences...
Until than...

Still slleping....uahhhh..

[Geo]

Hi Geo,
fine. If you tune coil and it's 32cm diameter you'll get more depth I think.

As you can see the TGS circuit is good for depth with small things... much like some PI detectors with small coils!

My only thoughts are about sensitivity to very small objects like 1eur-cent sized things... maybe the 32cm coil would detect them at lower distance
cause of field shape/density.

Let me know.

Kind regards,
Max

Hi Max
Later i will try to detect the 1euro-cent......... "a little hard to find this coin". As i wrote before i detect the 2euro-cent at 28 cm. I believe that about the same for 1euro-cent. Offcource in "all metal" mode. At afternoon i will try at discrimination made and i hope to be about the same (2..3 cm is not problem). Also i nust to remember to connect a diode 1N4148 at one LM308 (it missing.... pcb error)
Regards

[Geo]

Geo, welcome to the club! I knew you'll make it!

..

Hi Ivica.
Good news..... good detector with very good sensitivity.
Bad news............ very bad audio. When the signal is hight it sounds hard, bat when the signal is very low it sounds very low and not a real tone but a ks...ks....ks Agrrrr. I must try to put a audio with 555 so the tone to be the same ........ bip or not.
Who is your solution or your opinion????
Regards

[Qiaozhi]

Now, this one is more like it !!! 'Beast" in small package! But with double price...
I have 10 days to rethink on this....

Looks good, and it has two channels. The previous one was also a Velleman kit, but Maplins don't sell this one. In the UK it costs £355.

[ivconic]

Now, when problem solved...i have to apologise to KT315 again!
I deserved rotten tomato in face now! Why? Because that 1M resistor KT315 suggested, now is making a lot of sense! Geo do not make any mod with 555 until you try this one! Just put 1M across diode (parallel) as i posted on previous pages. It will improve audio very much, than you decide about modding it further or not.
Since TGSL is working in both modes very stabile i intend to retreive switch with 1M resitor...

Quiaozhi, that scope is approx. 450euros here in my country. To much for my budget. But also i am very tempted to buy it! I'll see i next week and decide...
Regards!

[ApBerg]

Disc pot

Hello Frends.

Porklvr:
Either change to a 10k Disc pot, or parallel a 10k fixed resistor across the 100k pot, and see what happens. It will very likely cause a different curve
to the Discrimination potentiometer effect (to be more like the original), but things should smooth out.

Your right ! , when placing a 10k resistor parallel across the 100k pot the erretic noise I had on high sens setting is gone !

Now I have replaced the 100k disc pot for a 50K pot. There is now and then some faint noise,... it lets you know it is still alive... I like that.

On a 20 cm opencenter coil a 1 euro is detect in air at 28cm, this is with the KT315 1M resistor

Best regards.

Ap

[ivconic]

OK. Problem is solved,TGSL is working just fine. But i experimented further.Some thing can not match here?
I cant achieve same oscilogramm at pin 1. of LF353 as ApBerg's posted here:

[ivconic]

And here is what i gainedd with good capactior...But i had to put 330pF to streighten up signal. When 100pf is on the place oscilogramm is still "broken" ...

[ivconic]

Experimented with values from 100pF to 330 pF. More i raise capcitance - the better oscilogramm, up to 330pF..
Except changing oscilogramm i havent noticed any other changes in TGS behavior!??
One more thing i noticed; i used 8ohm speaker at output. Audio was loud and clear but with ocassional false signals - beeps...
I added 10ohm resistor in serie with speaker (8+10=1 and no more false signals and beeps. Depth, sensitivity and GEB remained same - perfect! Only thing changed is audio level. Now audio is not loud but noticeable weaker...as expectable...??? What the heck is going on here? Despite TGSL works really good and calm....i am confused. I do not understand how speaker resistance can provoke false signal here??? Is it some kind of intermodulation here?
Looking back to partially correct Relic Hawk schematic i remember very well simillar audio and small transformer with some extra components there?
Did they have same problems in Minelab and solved it with that transformer?

I would not start this thing again but i need complete understanding of this.Also audio is weak now....Again (you'll laugh on me) if i put 1M resistor parallel to diode, even if i have 18 ohms now at output, 1M resistor causes same falses as from begining? Sort of "echo"; beep,beep,beep....once coin is moved over coil....
I 'll repeat; TGSL is working fine as i described....BUT I HAVE STRONG FEELING THAT PROBLEM IS NOT SOLVED COMPLETELY YET!??!!
Can you beleive this?
Nightmare!

[ivconic]

Max, GEo, ApBerg ...can you attach some 8 ohm speaker to your devices, turn Sense to maximum, Disc to minimum and test it on coin? Try to approach to coil with coin slowly just to start weak detection. Than remove coin slowly. Let's see is it gonna stop or continue with beeps...?
Also can you scope pin 1. of LF 353 and post shots here?
I am persistent on this. I will continue experimenting until whole thing become clear to me...

[Max]

And here is what i gainedd with good capactior...But i had to put 330pF to streighten up signal. When 100pf is on the place oscilogramm is still "broken" ...

Hi,
the 1M resistor is also in BandidoII schematic by default... it works cool when there is few erratic noise around... otherwise better avoid it at all.

The signal I see is with 330pf instead of 100pf ? Seems a square wave now !

I've tested my cap and it's ok... I've changed also it and all is the same... if I pull-out the lf353 I can see after the 100pf cap a perfect sinus signal like the one of Ap.Berg... but then when I mount LF353 it distorce the signal and I got the parabolic one with the damped oscillations.

So problem is at op. amp. inputs !

If I put a TLC2262 there instead of LF353 I got a near-to-sinusoidal wave... but different and with much less dumped superimposed signal.

TL072 there works exactly the same of LF353: signal is distorted.

The funny thing is that disc works pretty good... and it cannot detect an hammer at 1cm in disc mode!

So what's the story with LF353 ?

My actual part is LF353N from National, original part made in the 90's.

Any idea ?

Best regards,
Max

[Max]

Max, GEo, ApBerg ...can you attach some 8 ohm speaker to your devices, turn Sense to maximum, Disc to minimum and test it on coin? Try to approach to coil with coin slowly just to start weak detection. Than remove coin slowly. Let's see is it gonna stop or continue with beeps...?
Also can you scope pin 1. of LF 353 and post shots here?
I am persistent on this. I will continue experimenting until whole thing become clear to me...

Hi,
my yesterday scope signal was with an 8ohm speaker already there.
Yes I noticed too... 8ohm increase problems cause maybe more current drawn by output stage... that thing will cause small transients on supply rail that enter then the signal path and produce false signal cause all op amps. reside on the same line... they don't have e.g. separate decoupling and the like you can see in other circuits (often a 10-22ohm resistor + some 22-100uF capacitor at supply rails of ics).

The transients could also create some low frequency oscillation that intermodulate with useful signal... thus giving unpredictable behaviour.

I think that problem could be avoided using some optocoupler instead of transformer...

Best regards,
Max

[Max]

Hi,
here is the bandidoII part I mean... I remember that same problem happened in bandidoII : 8ohm speaker = bad, just good an apple computer 16ohm speaker with it.

So, of course, KT315 is right on mod... he followed Tesoro's rules ! so if you have to launch around rotten tomatoes... you have to point Arizona first ...

I'm joking now. Of course it works... and at Tesoro they made great designs!

but that will work ONLY if there is already really rare and occasional noise... otherwise it's a real boomerang.

Kind regards,
Max