TESORO GOLDEN SABRE

[Max]

Hi Qiaozhi and all,
I'm reading the George Payne's article... JC1 posted the link yesterday.

Found all very interesting... maybe I've read before... don't remember now.

Anyway, my problem now is on conventions

I mean in the Payne's article I read that ferrite rod gives "zero" point... ok... then I've looked again at an old patent of Jack Gifford and he said that pure mineral give RX shift of -90° : all fine, I remember this also.

But then Payne call it zero and Gifford -90° (referred to the osc signal).

I think that -90° is the right way... of saying that thing...

Then Payne wrote that normal ground could fall between 0° and -5° of shift... so more negative of ferrite imposed shift.

QUESTION IS: that means soil could give a shift from -90° to -95° or from -90° to -85° ???????

Kind regards,
Max

[Max]

- sens at max
- disc at min
- notch pot at min
- notch off

Huh! When i adjust:
- sens at max
- disc at min
I'll get bedlam of bleeps!!! Usually no bleeps if Sens at "6" and Disc at "2", if we consider pot scale as from "0" to "10"...
So!? If these works for you, than something is much different between my and your detector? What?
I had Minelab Musketeer Advantage on service last month. After fixing minor problem i tested it. Behavior was simillar to my TGSL. When Sense on it adjusted over "7" Minelab start screaming, Disc level hadnt influence...
So i thought it was normal...
What should be the problem here?!
Huh!

Hi,
yes is really strange. I noticed that with different components things change very much in TGS working about that... I mean noise.

I think your problem could be at LM308s if they are not original ones... I got enormous noise from the fake ones I bought some time ago...and at that time I really was impressed by that... before I had start thinking they aren't true National's parts.

Then replaced with secure originals I got much less noise... and good stability as described. Also with changing and testing TL071 and TL081 I noticed that but noise is always not much with those too.

With ST TL071 parts I got absolutely no bleeping at max sens.

But all these considerations are empiric... we have to look forward to insulate better the problem source. I strongly think that some kind of feedback occours between output comparators and preamp. along the supply rail, of course I'm not sure of that but solved the middle noise (fake LM308s) I suppose this could be the cause of bleeping at higher-max sens.

I think that problems are mainly noise from ICs but then, lowered noise, also propagation along supply line could be an issue.

I'm start thinking that an higher CMRR preamp will do better instead of LF353... but problem is finding as good sensitive as it for this design, and we know it's not easy.

LF353, if I remember well, has minimum CMRR of 70dB... not very good for a preamp directly connected to the same supply rail of output stages !

There are a lot with 120 or 130dB CMRR... much better but they lack on sensitivity cause of the input stage... example is the OPA227 with CMRR of 138dB ! Damn good... but I haven't and so I can't test it as preamp.

Best regards,
Max

[ivconic]

- sens at max
- disc at min
- notch pot at min
- notch off

Huh! When i adjust:
- sens at max
- disc at min
I'll get bedlam of bleeps!!! Usually no bleeps if Sens at "6" and Disc at "2", if we consider pot scale as from "0" to "10"...
So!? If these works for you, than something is much different between my and your detector? What?
I had Minelab Musketeer Advantage on service last month. After fixing minor problem i tested it. Behavior was simillar to my TGSL. When Sense on it adjusted over "7" Minelab start screaming, Disc level hadnt influence...
So i thought it was normal...
What should be the problem here?!
Huh!

[Max]

Hi Ivica. I will come with Bus (all the team will come with Bus).
About Anker ........... i have n't make the tests because i have problem with TGS pcb. When i will finish the TGS then i will make the test and to compare the detectors.
When I try to present the pcb it is dissolved immediately the photosensitive material. Maybe bad photosensitive material. I made about 10 pcbs without results . I think it is time to leave all these.......... maybe i am very old for these
Aby comment????
Regards

Hi Geo,
you can try reducing time of exposition... and making the solution more weak... to give you more time when removing eccess resist from it... but it could work or not depending of status of photoresist... sometimes the alteration is on 100% of it so you simply cannot reach your result with it.

Heat is the big problem for conservation of that boards... then time is the second critical factor (1-3 years good, 3-7years still good, more than 7years... is a challenge!)

The big problem with lowering the time is that some resist could remain there ! and is very tricky finding the right "seconds" of UV (yes seconds) you need to remove it good from board.

One time I repeated 22times the procedure to get a working PCB from old stuff...more than 10years old. After that I've made it good... but then considering the time and efforts required... it isn't any good and so I recovered boards and painted with new photoresist can all them. And now I make smaller PCBs at first attempt with them!

If you have many boards of good quality... I suggest you clean them one by one and buy a can to repaint again with fresh resist (I've done 35 small 10cmx8cm using a 12eur can), then find a cool place to store using a black paper or similar to cover from light.

Best regards,
Max

[Max]

Actually, this is very simple to measure. See attached image.
Switch to All Metal mode, and connect scope to point marked GEB. Then adjust GEB control until you have 0V DC. This should also work with a meter instead of the scope.

Hi Qiaozhi,
thanks for the hint...the other method! you gave me before...but I always follow the gate signal and RX one...to figure out the zero-crossing. I think that this is really useful for people that haven't or cannot use scope the right way... for one reason or another.

Kind regards,
Max

[Max]

Agree.That's why put tha 1M resistor as KT315 suggested.Much better audio response. But than bleeping occured!? Somehow i am wandering in the circle!? I do have oscilloscope, but better if i dont! It is old, obsolete,one channel and without internal synchro...!? Very,very old....Must buy new one asap!
BTW your story justify another thing; Relic Hawk is probably the best VLF ever....yet without speaker! Only earphones available with it...

Hi Ivconic,
with these controls:

- sens at max
- disc at min
- notch pot at min
- notch off

No bleeping at all. Nothing on air. Nothing in medium soils, detection is really good and deep.

I noticed that moving the disc pot further (say to the middle or more) and moving forward the notch pot (even with notch-off) I get sometimes some erratic bleeping due to maybe closed path and hi amplification. Probably supply rail is where the noise find its path to op. amps.

The problem was really huge with TL062 in place... that I've removed for the TLC2262.

You haven't notch on TGSL so it's not your problem there... but I think that a filtering on e.g. first preamp. would be always good... even if hi CMRR of modern op amps often don't require filtering for that.

Best regards,
Max

[Geo]

Toss it! I had simillar situation once.You may use thin marker and draw lines over photoprint....

Years are years .
I can't see so good

[ivconic]

Toss it! I had simillar situation once.You may use thin marker and draw lines over photoprint....

[Geo]

There is bus line Belgrade-Sokobanja twice daily....I am not sure about termin...If you come with car than it is 2 hours of driving in one direction.Also if you come with ca than you must pass highway, 30km away from Sokobanja...
Do you have Route66 Europe? Or Microsoft Autoroute? Easiest way to image this. I can send you plan with directions if you want?
But if you come with plane than you'll go directly to BG...
What was with your Anker?
Can you perform some fast air tests with few items? Coin 1cm, coin 2cm, Cola can.....

Hi Ivica. I will come with Bus (all the team will come with Bus).
About Anker ........... i have n't make the tests because i have problem with TGS pcb. When i will finish the TGS then i will make the test and to compare the detectors.
When I try to present the pcb it is dissolved immediately the photosensitive material. Maybe bad photosensitive material. I made about 10 pcbs without results . I think it is time to leave all these.......... maybe i am very old for these
Aby comment????
Regards

[Geo]

Also, try here -> http://maps.google.co.uk/maps?oe=UTF-8&hl=en&tab=wl&q=

Thanks Qoaozhi

[ivconic]

Actually i only reversed it!? Never mind....i'll do that later....Time to "sharpen" TGSL a bit more....
LOL

[ivconic]

Yes....and later add or substract some resistances on pot pins to achive full linearity....

[Qiaozhi]

Come to think...! Simillar should be done in Disc mode on other channel? Is'nt it? Or not...due relative position of Disc pot..?
Stupid me! Of course not! But another thing; low down Disc to minimum,measure second channel;
a) if not zero, than add or substract some resistance on one side of pot. to gain zero,
b) if zero, increase a bit and measure again;

Why? Try to achieve linearity in Disc range, cose i noticed some non-linear behavior also, there..
At the moment, if Disc pot. is lower than "2" than producing chatters more often, if Disc. pot is higher than "3" than no chatters at all...
That's why i suspected this stage, at first place...
I do beleive there are some differences in FET behavior also. I put J107, not BF245 or other.. ?
I think we are pretty close to solve this problem....
Thank you again Quiaozhi, your suggestion gave me some other ideas...
Best regards!

Also easy to do...
To get the correct minimum position for DISC, monitor the output of Q6 (above Q7) and adjust DISC control to get maximum voltage. This should then reject ferrous targets but allow all higher conductivity targets, such as foil, pull tabs, coins, etc.

[ivconic]

Come to think...! Simillar should be done in Disc mode on other channel? Is'nt it? Or not...due relative position of Disc pot..?
Stupid me! Of course not! But another thing; low down Disc to minimum,measure second channel;
a) if not zero, than add or substract some resistance on one side of pot. to gain zero,
b) if zero, increase a bit and measure again;

Why? Try to achieve linearity in Disc range, cose i noticed some non-linear behavior also, there..
At the moment, if Disc pot. is lower than "2" than producing chatters more often, if Disc. pot is higher than "3" than no chatters at all...
That's why i suspected this stage, at first place...
I do beleive there are some differences in FET behavior also. I put J107, not BF245 or other.. ?
I think we are pretty close to solve this problem....
Thank you again Quiaozhi, your suggestion gave me some other ideas...
Best regards!

[ivconic]

Heil Quiaozhi!
I'll do that! Thanks!