TGSL Tuning & troubleshooting

[johnsmith77]

Can you try to describe it more fully? I'm not clear what is happening.

As Ivconic answered once, it is possible to wire the DISC or GB pots backwards, so they work in opposite rotation from what you expect.

Please describe it more fully.

Regards,

-SB

I checked trim, pots, switch connections, it is ok.

On TR4 drain pin (disc channel) i see negative impulses.
And TR5 drain pin (gb channel positive impulses).

According to oscilograms in forum it shoul be on contrary.

So in TGSL_101 documentation i found usb cable connection: J2-1 (U101a pin 5 not inverted) goes to ground in coil head.
In forum i see (also your posts) J2-2, should go to ground in coil head.

Is there a mistake in that manual or in forum?


Thanks

[johnsmith77]

Can you try to describe it more fully? I'm not clear what is happening.

As Ivconic answered once, it is possible to wire the DISC or GB pots backwards, so they work in opposite rotation from what you expect.

Please describe it more fully.

Regards,

-SB

Mistake on tgsl 101 pdf. As i described in upper post.

But on TR4 drain pin (disc channel) i see negative impulses. Yours positive: http://http://www.geotech1.com/forums/attachment.php?attachmentid=3277&stc=1&d=119294976 3


And TR5 drain pin (gb channel positive impulses). Yours negative: http://www.geotech1.com/forums/attac...1&d=1192949787

According to your oscilograms it should be on contrary.


Reasons?:
Coils gives no double beeps sound, so not reversed rx or tx. Wrong phase shift with 29cm 1e detection and good ferrite rejection?
Even try a big and small off ressonance: add plus 1nf parrallel to RXc or to TXc. Later plus 10nf to RXc or to TXc. Just for trying to make another phase shift, to check if i can get other polarities.
I could not make signals at these points sinus shape opposite polarity. Can get only if signal shape rectangle, but it means nulling bad.

Thanks

[dfbowers]

I checked trim, pots, switch connections, it is ok.

On TR4 drain pin (disc channel) i see negative impulses.
And TR5 drain pin (gb channel positive impulses).

According to oscilograms in forum it shoul be on contrary.

So in TGSL_101 documentation i found usb cable connection: J2-1 (U101a pin 5 not inverted) goes to ground in coil head.
In forum i see (also your posts) J2-2, should go to ground in coil head.

Is there a mistake in that manual or in forum?


Thanks

Hmm.. I don't know why I didn't notice that before. Maybe a mistake in the TGSL_101 document. To check, only connect shields in coil to the cable shield.
That's the only way I have been building them lately and it improves performance in wet grass.

[johnsmith77]

Hmm.. I don't know why I didn't notice that before. Maybe a mistake in the TGSL_101 document. To check, only connect shields in coil to the cable shield.
That's the only way I have been building them lately and it improves performance in wet grass.

But this don't change Tr4, Tr5 drain signal polarities in mine TGSL. Another mistake in ?http://www.geotech1.com/forums/showt...hase#post61260

pictures F11-F17.

Can't still clear up.

Sorry for that, but have suspect that oscilograms F11-F17 was made with mixed scope leads: ground to signal, signal to ground.
Or rx, maybye tx leads reversed during scopping.
It is important to me, cause i want be sure i made TGSL correctly or not.

[simonbaker]

Mistake on tgsl 101 pdf. As i described in upper post.

But on TR4 drain pin (disc channel) i see negative impulses. Yours positive: http://http://www.geotech1.com/forums/attachment.php?attachmentid=3277&stc=1&d=119294976 3


And TR5 drain pin (gb channel positive impulses). Yours negative: http://www.geotech1.com/forums/attac...1&d=1192949787

According to your oscilograms it should be on contrary.


Reasons?:
Coils gives no double beeps sound, so not reversed rx or tx. Wrong phase shift with 29cm 1e detection and good ferrite rejection?
Even try a big and small off ressonance: add plus 1nf parrallel to RXc or to TXc. Later plus 10nf to RXc or to TXc. Just for trying to make another phase shift, to check if i can get other polarities.
I could not make signals at these points sinus shape opposite polarity. Can get only if signal shape rectangle, but it means nulling bad.

Thanks

Hi johnsmith77:

It would help if your links referred to the message containing the photo instead of the photo itself. Then we can see the context.

I'm not sure, but it may be possible that your coils are nulled to a different phase, which could make the oscilloscope signal at tr4 drain look different. It depends on which side of the minimum null point you choose. However, which side you choose null should not affect the basic DISC function. The target signal phase is the same regardless of null signal phase.

Are you sure you do not have the DISC pot leads reversed? Please describe more fully how your DISC control is working. For example, for each pot position, list all the metals that are rejected and which metals are accepted. Describe which position is clockwise (CW) and which is counter-clockwise (CCW). For example, some people divide the pot range from 0 to 10, with 0 meaning fully CCW.

Regards,

-SB

[simonbaker]

So in TGSL_101 documentation i found usb cable connection: J2-1 (U101a pin 5 not inverted) goes to ground in coil head.
In forum i see (also your posts) J2-2, should go to ground in coil head.

Is there a mistake in that manual or in forum?

I think that is definitely a mistake in the illustration -- good catch! We should fix that since it seems pretty essential. As dfbowers mentioned, the alternative wiring (with no grounding of RX coil) removes the possibility of error.

This highlights how darn difficult it is in these forums to divine a clear, accurate set of instructions for building some of these projects. Reading the threads is fraught with peril -- every other post has a mistake or disagreement. It really is an experimenter's game here. But Don's and Ivconic's manuals are the gold standard for now. It is very important to put such documents in a "sticky" post, like Qiaozhi did with Ivconic's material, and then allow continual editing to fix discovered errors. That way over time the information will become more thoroughly "vetted", tested, and reliable, and you'll always know where to find the latest version.

Of course if you're willing to tinker, analyze, and ask questions, you'll eventually get there regardless.

-SB

[johnsmith77]

Hi johnsmith77:

It would help if your links referred to the message containing the photo instead of the photo itself. Then we can see the context.

I'm not sure, but it may be possible that your coils are nulled to a different phase, which could make the oscilloscope signal at tr4 drain look different. It depends on which side of the minimum null point you choose. However, which side you choose null should not affect the basic DISC function. The target signal phase is the same regardless of null signal phase.

Are you sure you do not have the DISC pot leads reversed? Please describe more fully how your DISC control is working. For example, for each pot position, list all the metals that are rejected and which metals are accepted. Describe which position is clockwise (CW) and which is counter-clockwise (CCW). For example, some people divide the pot range from 0 to 10, with 0 meaning fully CCW.

Regards,

-SB

I have pot leads reversed, but i know it and when i say min, it is on pot max really. So there is no difference. I later change them. It is my mistake, which generally not effect tgsl working. It would affect i did not know it

It should be: CCW by mine opinion to R19, 3,3k; CW to R17, 100K

Foil, silver is rejected about at 5. Later check more.

I add some picture. It would help better compare to yours.

[johnsmith77]

Another pic.

[simonbaker]

I have pot leads reversed, but i know it and when i say min, it is on pot max really. So there is no difference. I later change them. It is my mistake, which generally not effect tgsl working. It would affect i did not know it

It should be: CCW by mine opinion to R19, 3,3k; CW to R17, 100K

Foil, silver is rejected about at 5. Later check more.

I add some picture. It would help better compare to yours.

Hi johnsmith77:

I think silver should not be rejected at 5. Maybe more like 10.

I am interested in seeing the oscilloscope traces comparing the TX oscillator (J1-1) to the gates of TR4 and TR5 at different pot positions (DISC pot for TR4 gate, GB pot for TR5 gate).

Put pot at 0, 5, 10 and show each pair of traces.

Regards,

-SB

[johnsmith77]

Hi johnsmith77:

I think silver should not be rejected at 5. Maybe more like 10.

I am interested in seeing the oscilloscope traces comparing the TX oscillator (J1-1) to the gates of TR4 and TR5 at different pot positions (DISC pot for TR4 gate, GB pot for TR5 gate).

Put pot at 0, 5, 10 and show each pair of traces.

Regards,

-SB

I don't have 2 channel scope. Will try with 2 channel pc scope, so signal shape will not be very nice with that kind scope at almost at the end of 20khz (sound card), but phase shift can be obtained

[simonbaker]

I don't have 2 channel scope. Will try with 2 channel pc scope, so signal shape will not be very nice with that kind scope at almost at the end of 20khz (sound card), but phase shift can be obtained

We'll see -- maybe too much frequency/phase distortion, but worth a try.

-SB

[johnsmith77]

I don't have 2 channel scope. Will try with 2 channel pc scope, so signal shape will not be very nice with that kind scope at almost at the end of 20khz (sound card), but phase shift can be obtained

I attach teoretical scope pic. I am 99% sure i will see the same on the scope.

Also i attach one more lower - yours real oscilograms, posted on page 57. I made from your pics, it will help to compare.

So mine impulses are shifted 90 degrees from yours. This will change polarity, not shape.
Why equal 90? I am so good to ballance coil 90 degrees from yours? Not 12 or 47 ? Think no. Reason is somewhere else.

[simonbaker]

I attach teoretical scope pic. I am 99% sure i will see the same on the scope.

Also i attach one more lower - yours real oscilograms, posted on page 57. I made from your pics, it will help to compare.

So mine impulses are shifted 90 degrees from yours. This will change polarity, not shape.
Why equal 90? I am so good to ballance coil 90 degrees from yours? Not 12 or 47 ? Think no. Reason is somewhere else.

Hi johnsmith77:

LF353 pin 7 is not a good reference for phase. Can you do same pics but referenced to TX signal?

Sometimes a 90 deg shift means wrong capacitor somewhere -- uF instead of pF -- for example.

But first let's compare waveforms referenced to TX signal.

Regards,

-SB

[johnsmith77]

Hi johnsmith77:

LF353 pin 7 is not a good reference for phase. Can you do same pics but referenced to TX signal?

Sometimes a 90 deg shift means wrong capacitor somewhere -- uF instead of pF -- for example.

But first let's compare waveforms referenced to TX signal.

Regards,

-SB

I solved it. I know why?

It depends on cable connection mode.

Connection "for wet grass" according to ussuall cable connection to coil, changes signal polarity on Tr4, Tr5, drains. Also it changes phase shift by 90 degrees.

Do you agree?

I am interested how is going coil nulling if someone is trying null, having standart cable connection on his TGSL and that someone compares his oscilograms to oscilograms of "wet grass" connection. The second person should think he made coil wrong, then he make another hoping then he will get oscilograms as got the first person, then again again and big trouble.
He can faill

Maybye it was disscused in forum before, but i could not find?

Thanks

[satdaveuk]

I think that is definitely a mistake in the illustration -- good catch! We should fix that since it seems pretty essential. As dfbowers mentioned, the alternative wiring (with no grounding of RX coil) removes the possibility of error.

This highlights how darn difficult it is in these forums to divine a clear, accurate set of instructions for building some of these projects. Reading the threads is fraught with peril -- every other post has a mistake or disagreement. It really is an experimenter's game here. But Don's and Ivconic's manuals are the gold standard for now. It is very important to put such documents in a "sticky" post, like Qiaozhi did with Ivconic's material, and then allow continual editing to fix discovered errors. That way over time the information will become more thoroughly "vetted", tested, and reliable, and you'll always know where to find the latest version.

Of course if you're willing to tinker, analyze, and ask questions, you'll eventually get there regardless.

-SB

I think thats a bit over the top you yourself and many others here have worked there *** off on this project, it cant be expected to be laid on a plate, the next thing they will be asking it to be built for them, this forum is a technical set up for experiments etc, anybody who didnt spot the error far as wireing inverted/non inverted on the circuit going to ground oviously hadnt done there home work previously before starting the project.
Far as reversal of wireing on the various pots..... so what, its only a matter of swaping to wires over so controls are going clockwise instead of counter clockwise, and dont say they got the wiper wrong I really cant see the big deal and if people on here are doing these projects cant sort that out then they shouldnt be attempting such projects in the first place.
My golden rule is when commencing the TGSL project use the origonal TGS circuit along side Ivionics and work between the two, then you cant go wrong.
Far as coil connections I personally found wireing up the same as Tesro do with there manufactured coils is best, I get few falses and its quiter, but of course I can only speak as I found in real use situations here in the UK.
This project was never a fool proof project for people with no engineering skills, they need at least a basic knowledge in electrical engineering and of course accurate test equipment.
Without either one or both of those things they are knackered, just wasting there money and everyone elses time.
And another golden rule is as said so many many times by Ivonics read the bl..... forums over and over again till its planted in the brain to how the TGSL ticks, all the imformation for this project is there in black and white, its no good reading bits of it, you need to read how it progressed, and may I add still is, its ongoing theres no final here and proberly still going when a lot of us are pulling daisys from below.( So dont lable anything as final)

You know simon I am a TV engineer by trade so Using test equipment and fault finding in the field of TV/Radio is like second nature , but even with those skills I had to get my brain in gear because of a doggy inductance meter duff chips and ongoing experiments, so how these lads with neither test kit and knowledge exspect to achive anything other than a non working project baffles me.
Or maybe im on a different planet or just plain old fasioned, if either please correct me and put me in my place.

Kind regards as always