TESORO GOLDEN SABRE

[waltr]

Did a quick compare of the OP07 verse TL071 data sheets.
What I see that may cause the OP07 to be not as goo is:
Input bias current is higher (nA vs pA) due to bi-polar inputs vs FET inputs.
Slew Rate and BW lower.

The OP07's best characteristic is Stability & low drift.
It also wants a full +-15V (all spec are for +-15V).

[Nandor]

Hi

In my recent build I have used OP07 to replace the LM308, I had no more "free" TL071. Using this opamp the detection distance has dropped about 5cm . I have tried LM741, TL081 TL071 all works fine but OP07 is weak.
Looking at the datasheet it a pretty decent opamp yet it does not perform well in this circuit.
Anybody some ideas? I have bought 10 pcs from Texas insturments they are not fake

[waltr]

hi to all.what is the last version of tgsl?? regards

https://www.geotech1.com/forums/forumdisplay.php?18-Silver-Sabre-Bandido-TGSL

[peyman 74]

hi to all.what is the last version of tgsl?? regards

[Nandor]

Add 1nF in plus for the Rx circuit and it will shift a bit the Rx. Theoretically the Geb phase shifter can do 45deg of phase shift, maybe your Rx signal is not in the range of that. No component is perfect so it could have only 40deg phase shift that could be a reason, it worked for me.
Read the topic, there are so many informations to learn this is only repetition!

[Mr.Jaick]

Scope waveform look ok but best if two scope traces are used. First on TX and then the other.
This is because ALL are relative to the TX signal and why it is called "synchronous detection'.

What are you using as the Ferrite sample??? There are Many different kinds and sizes of ferrite and not all can be used.
I use small thread cores from RF coil salvaged from very old radios. Some of the larger ferrite I have is never rejected.

Also, the adjustment of the GB pot is very, very sensitive. The tiniest movement can be too much.

What does the Coil RX Null look like?? We need to see RX at output of Pre-amp relative to TX to judge Phase shift and amplitude.
Look at Dbower's TGSL 101.pdf Scope pictures for examples.

i use toroid ferrites , new ones for power supply coils ,28mm
the tx vs rx was spouse to be the last pic sir , i forgot to share
here it is

the trigger source in scope is VERT not CH1(TX signal) , is that ok?

[waltr]

Scope waveform look ok but best if two scope traces are used. First on TX and then the other.
This is because ALL are relative to the TX signal and why it is called "synchronous detection'.

What are you using as the Ferrite sample??? There are Many different kinds and sizes of ferrite and not all can be used.
I use small thread cores from RF coil salvaged from very old radios. Some of the larger ferrite I have is never rejected.

Also, the adjustment of the GB pot is very, very sensitive. The tiniest movement can be too much.

What does the Coil RX Null look like?? We need to see RX at output of Pre-amp relative to TX to judge Phase shift and amplitude.
Look at Dbower's TGSL 101.pdf Scope pictures for examples.

[Mr.Jaick]

hello friends
i'm back again ,sorry
i can't reject ferrite with my tgsl
i've done whatever i know that could be effective
everything just looks perfect

take a look at these
scope set up for all pics: 2v/div , 20us t/div

1- pin 7 U102(gate of tr5) , GB pot min


2- pin 7 U102(gate of tr5) , GB pot max


3- mid leg of disc pot(min)


4- mid leg of disc pot(max)


5- Gate TR4 disc set at min


6- Gate TR4 disc set at mid range


7- Gate TR4 disc set at max


8- TX vs RX(output of pre-amp U101)
TX 2v/div and RX 0.5v/div

as you can see nothing is wrong here, i don't know where is the problem... i've tried many different null positions for coils, but nothing
the project looks at my eyes, smiles and says "that's not gonna happen buddy"

[waltr]

Taddaaaa I finally got it
when i was checking the U101 input and output , i realized that the pin 7(the original pin 1) and pin 8 are shorted!!!
i noticed the chip(LF353) is getting too hot , but i thought it is normal(yes i'm being dumb sometimes)
after refreshing all the solder joints i carefully followed the traces around inputs and output and find out that the stupid PCB manufacturer has joint the pin 7 and 8 !!!
because these two traces are a bit close to each other but not out of spec of the manufacturer, they told me they can etch down to 0.25mm at minimum , and my design was about 0.5mm !
the joint was extremely thin and somewhere very unreachable...
i ruined my 100k pot when i was trying to change it, it's a bit touchy but i saw the correct waveform for a second and i'm sure it's okay now, but couldn't capture it
i'll buy a new one tomorrow and test everything, hopefully it'll be fully functional, i'm pretty confident

so yeah fortunately it fixed, well thanks to you great people , i've learned a lot here just within a few days
truly you guys are some of the must helpful and useful people on earth, thank you very much for lessons
regards

Excellent. Very happy you found the problem and got it fixed.
Now waiting to hear how your TGSL performs.

[Mr.Jaick]

the schematic i have build now:
i have removed all those 100nF bypass caps

TGSL_schematic.rar

[Mr.Jaick]

no problem accept can confuse us if you only state U101-7


This is a problem and why Disc pulse changes level.
Check for bad soldering, shorts and layout. Does this chip have -6V on pin 4?


The PN4391 should work and is not the current problem.

god damn it , you're awesome waltr
who are you man? the next Jesus?
i appreciate your help, thank you

[Mr.Jaick]

This is my device, here you can see the Tx signal and the phase shifters output. Tx has 14Vpp clean sinewave
First Tx vs Geb and than Tx vs Disc square wave and last the Disc pot middle leg output as the Discrimination is at minimum and maximum level.

https://www.youtube.com/watch?v=VbjYgZoMek4

This is the video of the Jfet transistor signal vs Rx signal you can see that Geb is on the left and Disc is on the right side of the Rx signal
https://www.youtube.com/watch?v=mqPf72qbTeA

you're posts are very helpful thanks for sharing
i don't know how youtube's search algorithm works , cuz i searched about TGSL before and watched all the videos about it but never found your videos

[Mr.Jaick]

Taddaaaa I finally got it
when i was checking the U101 input and output , i realized that the pin 7(the original pin 1) and pin 8 are shorted!!!
i noticed the chip(LF353) is getting too hot , but i thought it is normal(yes i'm being dumb sometimes)
after refreshing all the solder joints i carefully followed the traces around inputs and output and find out that the stupid PCB manufacturer has joint the pin 7 and 8 !!!
because these two traces are a bit close to each other but not out of spec of the manufacturer, they told me they can etch down to 0.25mm at minimum , and my design was about 0.5mm !
the joint was extremely thin and somewhere very unreachable...
i ruined my 100k pot when i was trying to change it, it's a bit touchy but i saw the correct waveform for a second and i'm sure it's okay now, but couldn't capture it
i'll buy a new one tomorrow and test everything, hopefully it'll be fully functional, i'm pretty confident

so yeah fortunately it fixed, well thanks to you great people , i've learned a lot here just within a few days
truly you guys are some of the must helpful and useful people on earth, thank you very much for lessons
regards

[waltr]

3- U101(LF353) pin 6 , the problem (5v/div , 20us t/dev)
actually i accidentally switched the first op_amp of LF353 with second one when i was designing the PCB, my bad but it doesn't effect anything, does it??

no problem accept can confuse us if you only state U101-7

6- U101 pin 7 , this is the problem for that flat DC voltage (2v/div , 10us t/dev)
[ATTACH]49466[/ATTACH]

This is a problem and why Disc pulse changes level.
Check for bad soldering, shorts and layout. Does this chip have -6V on pin 4?

and to notice i used PN4391 instead of J107 , at that time i only found this FET and didn't know about BF245 so maybe i would change it in advance

The PN4391 should work and is not the current problem.

[Nandor]

This is my device, here you can see the Tx signal and the phase shifters output. Tx has 14Vpp clean sinewave
First Tx vs Geb and than Tx vs Disc square wave and last the Disc pot middle leg output as the Discrimination is at minimum and maximum level.

https://www.youtube.com/watch?v=VbjYgZoMek4

This is the video of the Jfet transistor signal vs Rx signal you can see that Geb is on the left and Disc is on the right side of the Rx signal

https://www.youtube.com/watch?v=mqPf72qbTeA