TESORO GOLDEN SABRE

[Max]

I think that i found the problem. As i saw at the datasheet for MPSA13 and BC517 there is a mistake at the pcb aboyt the position of MPSA13.The position is right for BC517 but not for MPSA13. I must reverse 180 degrees the mpsa13 to work. What to say. Ivconic or Max what transistor do you use..... mpsa or bc?
When i will go home i will try it

Hi,
yes you have to reverse 180° from BC517 position.
I use japan made C517 (that's the same of BC517) and it rocks.

Best regards,
Max

[ivconic]

MPSA14 with EBC ..... Yes i have to reverse it due oposite e and c ...
You solved problem GEO!

[Fred]

Hi,
I have been reading your posts with great interest, thanks for sharing your experiences.I have learnt a lot.
About coil nulling, i wonder why you dont measure your voltage at output of 1st opamp instead at the coil istself? this way measurment would be more precise (already amplified), no influences from multimeter or scope probes ,and connecting cable capacitance and resistence already there, as in final use.
Or i am missing something?
regards,
Fred.

[Max]

Hi,
I have been reading your posts with great interest, thanks for sharing your experiences.I have learnt a lot.
About coil nulling, i wonder why you dont measure your voltage at output of 1st opamp instead at the coil istself? this way measurment would be more precise (already amplified), no influences from multimeter or scope probes ,and connecting cable capacitance and resistence already there, as in final use.
Or i am missing something?
regards,
Fred.

Hi Fred,
you are right... one can also use just 1st preamp to do that... and personally I've made too a number of times... but just prefer having passive components on rx coil when null with scope... cause I actually want measure absolute value without considering other scaling factors like gain of first amplifier.

Now a very easy test I made, after measuring with just scope I connect coil to pcb and read output at first preamp... and of course I read the value measured by scope scaled by gain of first stage... but I look also for distortions due e.g. to bad capacitive effects on preamp... and compare with (perfect) sinus I get from just probe measure...

That way I'm almost sure (if I see again perfect sinus) that 1st preamp doesn't introduce noticeable distortion and similar problems.

But that's just my way of testing things...and others would surely disagree repeating things in the two ways.

Best regards,
Max

[Qiaozhi]

Hi,
I have been reading your posts with great interest, thanks for sharing your experiences.I have learnt a lot.
About coil nulling, i wonder why you dont measure your voltage at output of 1st opamp instead at the coil istself? this way measurment would be more precise (already amplified), no influences from multimeter or scope probes ,and connecting cable capacitance and resistence already there, as in final use.
Or i am missing something?
regards,
Fred.

No - you've not missed anything. That's the way I do it.

[ivconic]

Yes this will do, in case you are using exact coil on exact device. But if you want versatile coil, better to null it directly attached on scope. Front end can add some noise,jitter,suck some interefernces due some bad component etc... I choose this way due fact that have 8 devices and 16 differnet sized coils...Many of components arent new, taken from scraped electronics...I do have doubts in some of those.
But anyway, you have right. Max done the best method - both. First without front end and after than with. So you can easily see eventyal differences...
Both ways are correct.

[Unregistered]

Hi
Thanks to all for your answers!.I understand your respective points.
Basically,you are doing so for research purposes, If you want to build ONE (perfect) detector, just using the preamp output is probably the best way.
Ivconic, i work often with radio frequency,so i know what you mean , an "unmached" input can raise the noise figure etc...tsss...perfectionists!
Keep the good work!
Tomorrow i will look for a piece of acrylic glass to make my coil form.

(Im Fred, but i don´t have my password here so i can´t register.)

Best regards!,

Fred.

[Qiaozhi]

Yes this will do, in case you are using exact coil on exact device. But if you want versatile coil, better to null it directly attached on scope. Front end can add some noise,jitter,suck some interefernces due some bad component etc... I choose this way due fact that have 8 devices and 16 differnet sized coils...Many of components arent new, taken from scraped electronics...I do have doubts in some of those.
But anyway, you have right. Max done the best method - both. First without front end and after than with. So you can easily see eventyal differences...
Both ways are correct.

For this exercise, the noise generated in the preamp should not be a problem. Don't forget that this is really the signal that you're sampling, not the one from the coil. If you have noise issues here, then there's a real problem. Also remember that the coil will only be properly balanced for the frequency it was designed for. The only way you can keep your coils consistent between detectors is to put the tuning capacitors in the coil, not on the PCB.

[Geo]

Works

Ok the GoldenSabre works. I rotate the MPSA13 180degrees and now it is ok. I connected it only in manual mode but i dont like it. I null exactly the coil (with the scope at the out of LF353) but i did not connected any capacitor to the RX coil for fine tuning (there is only one capacitor 15nF on the board).
Results:
Audio........ very low.... it needs a audio amplified (LM380... 386). As i see with the scope there is change in the signal that speeker don't sound, so we loose depth.
Sensitivity........ medium.... 2euro coin at 25 cm , 50Euro cents 25 cm, 2cents at 18cm, aold greek coin 30mm at 28...30 cm.
MAybe today or tomorrow i will try to fine tune the coil and to see the max semsitivity of this detector. If the sensitivity is near at my yesterday test then Ankerr SS-60 is Big Winner.
Max can you tell me at what distance you can detect a 2Euro coin???
Regards

[ivconic]

Ok the GoldenSabre works. I rotate the MPSA13 180degrees and now it is ok. I connected it only in manual mode but i dont like it. I null exactly the coil (with the scope at the out of LF353) but i did not connected any capacitor to the RX coil for fine tuning (there is only one capacitor 15nF on the board).

Results:
Audio........ very low.... it needs a audio amplified (LM380... 386). As i see with the scope there is change in the signal that speeker don't sound, so we loose depth.
Sensitivity........ medium.... 2euro coin at 25 cm , 50Euro cents 25 cm, 2cents at 18cm, aold greek coin 30mm at 28...30 cm.
MAybe today or tomorrow i will try to fine tune the coil and to see the max semsitivity of this detector. If the sensitivity is near at my yesterday test then Ankerr SS-60 is Big Winner.
Max can you tell me at what distance you can detect a 2Euro coin???
Regards

Geo, now add 1M resistor, if you want better audio response...
About performances;
you are anticipating too soon! Dont be so sure about Anker efficiency over TGS UNTIL YOU TOOK BOTH OUTDOOR and see real behavior on the ground. I am sure Anker doesnt stand any chance on the ground, comparing TGS. But, i dont need to tell you this, you will see yourself.

So i'll repeat once again, but for sure last time, not for you but for those unawared yet;
Tests performed in the air are not reference. Not accurrate. Detecting single coin in the air, on 40-50cm distance, DOESNT MEAN A THING!
Real detection is when coin is burried in the ground, COVERED WITH SOIL!
As real time prospector, i had chance to fully tested over 50 different detectors, on the ground, under REAL conditions. I am free to form opinion on that. Detectors like Anker, with output boosted that much, are absolutelly UNUSEABLE on some type of soils - most of types actually. You can easilly detect coin at 50 cm in the air. But in the ground it can NOT see same coin, even on 1/3 of air distance. TGS on the other hand is pretty optimized design with simillar air/ground performances (that's why is my favorite)....So distance you see in the air is more likely to be seen in the ground also, dependes mostly of quality you gained making it.
Dont guess me wrong, i have nothing against Anker....but last week i had chance to see on of those, tested, compared.....and when adjusted to work calm on the ground....it is very poor on performances, much,much under TGS...
Wish you luck!

[ivconic]

For this exercise, the noise generated in the preamp should not be a problem. Don't forget that this is really the signal that you're sampling, not the one from the coil. If you have noise issues here, then there's a real problem. Also remember that the coil will only be properly balanced for the frequency it was designed for. The only way you can keep your coils consistent between detectors is to put the tuning capacitors in the coil, not on the PCB.

I do not agree there. We have different points of view. I already explained that i plan using my coils on quite different machines...I want my coils to be as much versatile as possible. I do not want to "tie up" specific coil to specific detector. Just look Fisher,Garret,Whites,Minelab....you are not pushed to buy exact coil with exact machine. If they have 1000 Spider coils available at shop, you can choose any of them to use with you...let's say CZ5, for example....
I simply refuse to beleive taht they nulled every coil with every machine in producing process..!? White's also; i tested some old coils with brand new machines - working perfect!? How come?
About tuning capacitors; yes, here i agree. You can achieve better performances if coil is fine retuned with it. But this you can do after basic nulling, on some specific machine...
Regards!

[ivconic]

I forgot to mention one fact; coil came with 1266, small spide 8", when tested with CZ5 is working perfect. Coil came with CZ5, 27cm Spider is working perfect with 1266...? How come?
I do have many other examples...dont want to bug much.
We missing the point here. My point is to null coil with less residual voltage possible on BASIC frequency. In TGS case freq. is 14kHz. So later i will have less error if that coil is used with Bandido, 10kHz...for example. Or i can decide to rise frequency to 12kHz...even less error. I dont need to null it using front end signal? Why should i do that?
I am standing to this point. Dont think further debate is needed on this. Everyone of use should use own method, which find the best for him. It is like debating on women!
To individual...no need to debate on this...
Regards!

[Geo]

Hi Ivconic.
I agree with you but.....
I understand that there is big difference between air and ground.If one detector locate a coin on the air at 40 cm it will detect it at 20... 30 in the ground. But if detect a coin at 20 cm in the air it can't detect it at 25 cm in the ground. This is the point that i say that SS60 is winner. If i will detect with TGS a 25mm coin (2euro) at 30++cm at the air then i will compare it with SS60.
The problem with my TGS is that i can't locate a coin at the distance that you say that you detect. Maybe when i fine tune the Rx coil to detect it at same or near distance. I use a 32cm DDcoil so i must detect it at 30++cm.
Btw do you use an extra capacitor at the Rx coil? (15nf on the board and other cap on the coil)
Regards

[ivconic]

No. I am using original setup as on schematic posted earlier.
My coil is 27cm (255x137) as described earlier..
To gain more depth you should null coil proper, as described earlier...
With 32cm coil i think you should detect 2cm coin at at least 40cm in the air and for sure at 25cm in the ground...maybe few cm more, depends of soil mineralization - most important!
For 32cm coil use 0.3mm wire, and approx. 92-95 turns for TX and 95-100 turns for RX, inductances; 6mH for TX and 6.5mH for Rx....
Disc.pot to "2", Sense pot. to "8", in Disc mode of course....
If you add 1M resistor you'll have much better audio response but also risk to ocassional chatters appear...again mostly depend of soil type...
Pleas when finished, DO some ground tests with both machines and post results here!
Regards!

[Max]

Ok the GoldenSabre works. I rotate the MPSA13 180degrees and now it is ok. I connected it only in manual mode but i dont like it. I null exactly the coil (with the scope at the out of LF353) but i did not connected any capacitor to the RX coil for fine tuning (there is only one capacitor 15nF on the board).
Results:
Audio........ very low.... it needs a audio amplified (LM380... 386). As i see with the scope there is change in the signal that speeker don't sound, so we loose depth.
Sensitivity........ medium.... 2euro coin at 25 cm , 50Euro cents 25 cm, 2cents at 18cm, aold greek coin 30mm at 28...30 cm.
MAybe today or tomorrow i will try to fine tune the coil and to see the max semsitivity of this detector. If the sensitivity is near at my yesterday test then Ankerr SS-60 is Big Winner.
Max can you tell me at what distance you can detect a 2Euro coin???
Regards

Hi Geo,
I use more often the 1eur coin in tests: I detect it at 35cm loud
If remember well 2 eur coin at more maybe 37cm... I will test again and report here.

That depth are only given by big coils in air... I mean not 8'' and the like but the Ivconic's 255x137mm or other in the 10'' range coils.

You need to null the coil for minimum voltage and on mine I get with a bit of patience something around 5mVpp. I cannot reach at now less than these voltages cause coil is big and overlaps are about critical.

You also need all the rest... I mean coil must be fixed very well in epoxy cause any movement will degradate your SNR cause of the integrations... and so average of signal.

On the ground the behaviour is good if you perform tests on medium soil and tune good way the GEB trimmer (use ferrite but don't null totally... just to ear small "cracks"... then test silver response after that).

Best regards,
Max