TESORO GOLDEN SABRE

[ivconic]

Hi Ivica.

How is the weather at Beograd?????
Regards

Dont really know for sure? Here at my place rains,rains,rains....Today a bit better. But you have luck Geo, it is getting bettter. On November the 2. will be sunny an shinny! Wish you nice trip!
Regards!

[Geo]

Hi Ivica. Thanks for info
I will arrive at 2 Nov morning.
My regards

[Darko]

When I turn my TGS on, while batt check audio tone is loud enough, but when batt test ends, audio going to be very weak in normal operation. Some short time everything was been ok but then difference between tone loudness in batt test and working mode now has very big. Coil is 255x137 ivconic data, on former Max posted here, but TX freq is 15,30????I’m sure that wire diameter is 0.25 without varnish. What should be I check first? Voltages seems to be ok. +8V and -6,12V. Please help. My English is too bad to explain better.

[Max]

When I turn my TGS on, while batt check audio tone is loud enough, but when batt test ends, audio going to be very weak in normal operation. Some short time everything was been ok but then difference between tone loudness in batt test and working mode now has very big. Coil is 255x137 ivconic data, on former Max posted here, but TX freq is 15,30????I’m sure that wire diameter is 0.25 without varnish. What should be I check first? Voltages seems to be ok. +8V and -6,12V. Please help. My English is too bad to explain better. [/font]

Hi Darko,
the battery checker is always loud cause the op. amp. that battery checker use gives a strong commutation when batt is ok... so it's normal it is very loud.

When it stops the fet at battery checker "open" circuit from it to output so your output depends then just of output of signal path amplifier (comparators) that drive the last LM358 half connected to audio stage.

Voltages are ok: +8 , -6.2 are fine. If you used Ivconic's data also coil must be ok.

Your frequency is no good... good operations are under 15KHz... with data provided you must gain min. 14.6 to 14.8 Khz maximum.

About coil you need tightning wire with rubber or plastic adesive tape or a cotton cord... and the like... cause if not tight you get bigger frequency from it.

That's could be a problem cause of some capacitance reactance at that higher frequency in the circuit , so stay under 15KHz, possibly under 14.75Khz.

So I suggest you check coil again and oscillator section, cap values, zener diode etc... you must reach something around 14.7KHz first of all.... then you'll focus on optimization. Of course, that will be with shield too, that you always need for real use on soil.

Audio is always weak at good GEB setting: this is an original drawback of TGS... so you have to make some mod to gain better.

For audio you have, basically, two choices :
- use a 2K2 resistor instead of 33K at last LM358 will rise up audio easy, but more instability could be the price
- use the 1Mohm resistor at D12 like Ivconic showed in schematic of TGSL, with the switch I mean: same thing, strongest audio from far targets too but you'll have some instability more

Or both things... if your instability level is low enough to leave you in conditions of using detector on real soil.

Then using headphones is always better: you don't lose even smaller sounds with them... where instead using speaker you can lose much of them.

Kind regards,
Max

[nelson]

This is tru.
When you setup GEB on the field, TGS works great.
I had the same problem, but on the beach with black sand, after i tried a few GEB settings, i got good ground balance.
Now my question is if is possible to use a smaller variable resistance on GEB. This because setting it on the rigth point was a little difficult, while the pot has a very narrow way to reach the correct setting.
Also, what about setting GEB has an external control on TGS?
Regards
Nelson

You dont need to move Disc. pot to reject ceramics at TGS. You can adjust it with GEB trimmer to void ceramics,hot rocks and simillar. But you have to take it there and adjust it at that moment under those conditions...It will work just fine....of course you must make good coil...DD coil!
Regards!

[Darko]

Max, thank you for hints. I’l will check all as you sugested.
Speaking about coil, I quite sure that i tight wire good with cotton cord. Maybe my former is’nt good. I suspect on circumference of D shape is not good? It is around 66cm?

For audio you have, basically, two choices
use a 2K2 resistor instead of 33K at last LM358 will rise up audio easy, but more instability could be the price

2k2 is already there and no instability at all because of veak sensitivity,

-use the 1Mohm resistor at D12 like Ivconic showed in schematic of TGSL, with the switch I mean: same thing, strongest audio from far targets too but you'll have some instability more

There is no differene’s if I put 1M resistor or not. Without 1M, TGS have behavior like a there is 1M resistor. Will see when I check once more all of capacitors and semi’s in osc section.

Best regards,
Darko

[Fred]

Hi,
The Zener diode is also very important for frequency,you should check its value and polarity.
Fred.

[Max]

This is tru.
When you setup GEB on the field, TGS works great.
I had the same problem, but on the beach with black sand, after i tried a few GEB settings, i got good ground balance.
Now my question is if is possible to use a smaller variable resistance on GEB. This because setting it on the rigth point was a little difficult, while the pot has a very narrow way to reach the correct setting.
Also, what about setting GEB has an external control on TGS?
Regards
Nelson

Hi Nelson,
yes we can try with an external pot... but problem is that resolution of normal 3/4 turn pots is that you cannot move easy between narrow small resistance values... very difficault.

Solution could be a multiturn pot there from 3 1/2 turns to 10 will be ok I think. Then one must perform that setting each time using all-metal mode. In bandidoII geb is that way: 3 1/2 turns pot wirewound.

The fact GEB is so critical sometimes is related to different soils... that's why in bandido and others there is an external geb pot.

I haven't tested yet but I'd like to do... cause could be positive for a better stabilization from one soil to another.

Kind regards,
Max

[Max]

Max, thank you for hints. I’l will check all as you sugested.
Speaking about coil, I quite sure that i tight wire good with cotton cord. Maybe my former is’nt good. I suspect on circumference of D shape is not good? It is around 66cm?

For audio you have, basically, two choices
use a 2K2 resistor instead of 33K at last LM358 will rise up audio easy, but more instability could be the price

2k2 is already there and no instability at all because of veak sensitivity,

-use the 1Mohm resistor at D12 like Ivconic showed in schematic of TGSL, with the switch I mean: same thing, strongest audio from far targets too but you'll have some instability more

There is no differene’s if I put 1M resistor or not. Without 1M, TGS have behavior like a there is 1M resistor. Will see when I check once more all of capacitors and semi’s in osc section.

Best regards,
Darko

Hi,
my circumference of nails pattern is exactly 64.5cm.

If using 1M resistor is all about the same you probably have some bad thing before comparators... could be some IC like TL081 or the like... cause I noticed a huge difference when 1M is in the circuit:

comparators saturate at minimum signal , even from far and very weak from small targets... where with just diode it isn't... and I get a very small audio response like tic-tic from speaker... not a good and loud tone.

With just diode the response is progressive... nearest the target, louder the response; with 1M instead is a totally flat response, always loud... independently by target size or distance...so kind of real comparator action (with very sharp rise/fall edges).... also you can understand if target is far or near just hearing the sound lasting less or more, but not about intensity that's always the same.

Check the LM308s part before comparators... also try different ICs there.

Best regards,
Max

[Darko]

Hi,
The Zener diode is also very important for frequency,you should check its value and polarity.
Fred.

Thanks Fred,
I already leplace Zener with new one. Also replaced 1N4148 near Zener. I suppose my coil is not good. I making former in way to design it in eMachineShop, then print drawing and glue to the wooden board. I'm designed it following pictures posted by Max. I dont know where i'm make mistake in drawing former but for sure fault occured.

[Darko]

Hi,
my circumference of nails pattern is exactly 64.5cm.

If using 1M resistor is all about the same you probably have some bad thing before comparators... could be some IC like TL081 or the like... cause I noticed a huge difference when 1M is in the circuit:

comparators saturate at minimum signal , even from far and very weak from small targets... where with just diode it isn't... and I get a very small audio response like tic-tic from speaker... not a good and loud tone.

With just diode the response is progressive... nearest the target, louder the response; with 1M instead is a totally flat response, always loud... independently by target size or distance...so kind of real comparator action (with very sharp rise/fall edges).... also you can understand if target is far or near just hearing the sound lasting less or more, but not about intensity that's always the same.

Check the LM308s part before comparators... also try different ICs there.

Best regards,
Max

Sorry,sorry sorry.... Freq is 14.631. I check again now with SpectraLab. My multimeter is liar! I must buy new,good one. So, nothing wrong with my coil i build as ivconic and Max described here. Also LM308 s i will replace when i get new ones. Thank you Max. I think problem is solved.

Best regards,
Darko

[ivconic]

"..My multimeter is liar!..."

Use 5kg hammer and kill it!
I still beleive you have problems with coil balance. Why? Simply, as you told me berfore, you dont have neither good unimeter, neither scope...to null coils. The hell!? How did you expected to null coils accuratelly?
In the past i also nulled few coils relying on my "hunch" and audition....Later when checked on unimeter or scope, i found out some residual voltages over 50-80mV..!!! "Hunch" my ***! I killed those coils with that famous hammer...of mine!

[Geo]

Ivica who is the voltage tension at Serbia (230V or 110v). I want to know what to do with chargers for (video camera and mobile phone).
Regards

[Darko]

"..My multimeter is liar!..."

Use 5kg hammer and kill it!
I still beleive you have problems with coil balance. Why? Simply, as you told me berfore, you dont have neither good unimeter, neither scope...to null coils. The hell!? How did you expected to null coils accuratelly?
In the past i also nulled few coils relying on my "hunch" and audition....Later when checked on unimeter or scope, i found out some residual voltages over 50-80mV..!!! "Hunch" my ***! I killed those coils with that famous hammer...of mine!

Yes ivconic, you are right in that way, but my problem with TGS was't nulling but sleepy LM308AN, both of them, just as Max sugested to check them and replace. I don't have problem with nulling at all! I nuling using AudioTester Osci even i knew you disagree with this way of nulling. I think, software like is Audio Tester is good enough for nulling coils and trick is only in proper calibration of these. I order pair of LM308H in metalic case like as you sugested here and I'm sure TGS will work great, just like before i burn it! Anyway, thank you for sugestions and help. About my unimeter,I'll just readjust him and will be good until i buy new one. Then i will try hammer on it.
Regards,
Darko

[Max]

"..My multimeter is liar!..."

Use 5kg hammer and kill it!
I still beleive you have problems with coil balance. Why? Simply, as you told me berfore, you dont have neither good unimeter, neither scope...to null coils. The hell!? How did you expected to null coils accuratelly?
In the past i also nulled few coils relying on my "hunch" and audition....Later when checked on unimeter or scope, i found out some residual voltages over 50-80mV..!!! "Hunch" my ***! I killed those coils with that famous hammer...of mine!

Hi,
...yes I know what you mean... really coloured way to say that!

Sometimes better using hammer and take some rest from multimeters and other strange things...I mean when they make you crazy!

I think that also a good old AC millivoltmeter could be better of many made in somewhere things... when they are just crap instruments.

That's why I suggest people here of rediscover some old funky projects with just one op. amp. to apply on some old analog meter... much much better than a 2eur no-brand-multi-lies-meters.

Best regards,
Max