TESORO GOLDEN SABRE

[sinclairuser]

it looks like a board revision.

[paku]

can someone explain me about this Jumper Setting

[Gwil]

Thanks.

[Silver Dollar]

Opps I had meant to post the schematic;

Original




AB/C

[Davor]

AB->C is a mod on Musketeer IGSL that turns a Tx oscillator from class AB to class C after oscillation is established. It improves power consumption and also signal purity to a small degree. The concept may be extended to other oscillators as well.

[paku]

what is that

[Gwil]

Can someone tell me where I can find a description of the "AB/C configuration"? I tried a search but nothing came up - I must have been doing something wrong.

Thanks.

[Silver Dollar]

I was just playing with the minelab oscillator and managed to get it to run at 14.7 khz
just like the original TGSL one and using the AB/C configuration it only draws around 4ma!

I needed 0.124 uf to tune my 1 mh coil to 14.7 khz. It puts out 19.3V peak to peak and
draws 3.9 ma in AB/C mode (normal mode is 9.9 ma). I had another coil that was a little off
somehow so had to adjust the resistor to the -9v to 770k (from 681K) to make sure it stayed
running.

It's a nice oscillator. I could adjust the frequency from 9 khz to 15 khz and the amplitude
stays the same. Current is up there without the AB/C mod but it traps a lot of current in the
coil (150 ma!) and with the mod the power use is reduced when the negative supply comes up.

[manny77]

Manny wrote:

Speaking about tx oscillator, i see not perfect shape of sine wave (distortion on the top). I know that early in the forum someone investigated that issue. Anyway i don't see if a clear solution for that problem was found. Is a good, almost perfect, sinus desirable? IGSL, if i'm not wrong, has a variable resistor for R3 to adjust sine distortion. Can i apply that to tgsl edu? Which are the benefits?

Jerry wrote:
Yes you can apply that to the TGSL. I tried it a couple years ago. It will clean up the TX waveform for a nice clean sine wave. However, I was not able to see any difference in performance in either air tests or in the field.

Jerry

Today I did some mods to my TGSL.
Changed R3 fixed 47K to trimmer 10 turns 100K. Tuned to find a good sine waveform.
I can't notice depth improvements as you already tested Jerry. But I've examinated received waves that are much more clean so discrimination is slightly better.

Silver Dollar wrote:

I found a difference on my Bandito. A pure sine wave got a bit more in air test but
A slight distortion is better for falsing. It hits the rail and stops amplitude variations.

For now I tested it only in air. Hope less falsing as you stated SD.

Disc pot was causing beeps when rotating before this mod. With oscilloscope i saw the wave changing and producing jagged profile, very ugly.
Now LF353 pin 1 is almost SINE WAVE. Only cutted on lower part because not symmetric rails (+8V and -6V). This seems to be not a problem anyway...disc pot now act like charm, without beeps on entire rotation.

During TX refiniment with new Trimmer R3 i notice that amplitude could change a little and frequency too! I saw that rotating it to make worse sine (with distortion on top) frequency goes lower (from 14.3 KHz towards about 13.7 KHz). Testing with an euro coin while rotating trimmer in that direction, detection distance is a little better. BUT waveform is worst! Probably a little lower frequence is tuned better with RX...or amplitude of tx is little (very few) more... I honestly don't know. Anyway for me 14.12 KHz seems the best value. So i adjusted trimmer to perfect sine...rising freq...Losing 2 cm of more detection.
To mantain this little more gain i achieved (previously, with lower freq.), I thought to add a little more capacitance to C2. Inserted a capacitor bank tester in parallel to it, trying to fit the right value. 1nF seems to lower freq. exactly to 14.12 KHz. And NOT CHANGING MY PREVIOUS PERFECTLY ADJUSTED ROUND SINE WAVE! So I win a couple cm of detection... Nice.

After this mod I installed my brand new NJM2068 instead of LF353. See post #6 from Davor here:

http://www.geotech1.com/forums/showthread.php?21579-TGSL-EDU-Mod

It give me some 2cm more (not 5), but I have to test it outside...in real field too. Feelings are good...

Total gain in depth today after these mods: about 4-5 cm IN AIR. Total distance for 1 euro coin: 31 cm (32 broken signal...very faint. 30 almost perfect beeps).

My coil is 27cm, homemade, you can see it in my avatar
Nulled at 280mVpp (pin7 U101a).

[paku]

is that have anyone test this TGS Board

http://eversite.org/download/TGS.zip

[Silver Dollar]

I found a difference on my Bandito. A pure sine wave got a bit more in air test but
A slight distortion is better for falsing. It hits the rail and stops amplitude variations.

I made a new minelab style coil and have something funny going on with it. I nulled
it by connecting to TX and scoping the RX wires directly. I nulled it making sure to be
on the right side of null with min amplitude (10mv) but when connected to
the PCB a scope from ground to one of the RX points on pcb shows 850 mv. So I
grounded one RX wire and then got 2v! This is right where the coil wires enter the pcb
so no effect from opamp...

I ran the TX and RX wires separately and a shield wire (tied to gnd at PCB) maybe
needs the Tesoro wiring scheme?

[Jerry]

Speaking about tx oscillator, i see not perfect shape of sine wave (distortion on the top). I know that early in the forum someone investigated that issue. Anyway i don't see if a clear solution for that problem was found. Is a good, almost perfect, sinus desirable? IGSL, if i'm not wrong, has a variable resistor for R3 to adjust sine distortion. Can i apply that to tgsl edu? Which are the benefits?

Yes you can apply that to the TGSL. I tried it a couple years ago. It will clean up the TX waveform for a nice clean sine wave. However, I was not able to see any difference in performance in either air tests or in the field.

Jerry

[6666]

Good Questions Manny, interested in the answers to.

[manny77]

I've some questions about my tgsl:

When i firstly build it, kit contains TL071 and not LM308. I know that original LM308 was superior op-amp but non easy to find and pricey... So i mounted OP07 for u104 and u105. Not a big step ahead but probably a little better on the field. Searching for optimal op-amps i see that OP77 are something like state of the art... I have to expect another improvement or nothing so special mounting them?
I could have them easily...

OP77 datasheet:http://www.datasheetfind.com/details/1223605.html

Seeking for tgsl refinements i'm waiting for NJM2068 as frontend for rx coil, replacing LF353 (Thanks davor and silver dollar)...hope in sens benefits...

Speaking about tx oscillator, i see not perfect shape of sine wave (distortion on the top). I know that early in the forum someone investigated that issue. Anyway i don't see if a clear solution for that problem was found. Is a good, almost perfect, sinus desirable? IGSL, if i'm not wrong, has a variable resistor for R3 to adjust sine distortion. Can i apply that to tgsl edu? Which are the benefits?

Too much questions? hope not!
Thanks in advance

[zoomtronic]

I just were playing with coil balance using USB Oscilloscope







On RX coil i just placed function generator tuned to 14.5KHz
and that is the channel 2 on scope,
on first scope channel i connected RX coil
And moving coils across each other i got perfect null position