TGSL Tuning & troubleshooting

[simonbaker]

hello simonbaker
that video in youtube not me . I want to mention I ues same coin But I get 22cm on my tgsl.
and I tried what you said but did not succeed is still weak sensitivity.
Thank you for your interest

Greetings

Hi salih:

Sorry, I misunderstood about the video. I understand it is not your MD now.

With your TGSL, after modifying the sensitivity, what happens if you turn the pot to max sensitivity? Do you hear any beeping of any kind?

Please do this:

1. Put a jumper across your RX coil leads (shorting the RX coil).

2. Measure the DC voltage at the output of each LM308 with a sensitive voltmeter using millivolt scale.

3. Remove the jumper from the RX coil leads.

4. Measure the AC voltage at the output of each LM308 with a good voltmeter that can measure up to 15 kHz.

Tell us the results.

Regards,

-SB

[golfnut]

mylar

Mylar is an insulator and can has zero metal content.

However you can coat it in metal and it can look really silvery then.

DF loop aerials have non ferous solid metal tubes around their windings.


used to see them on top of ships masts - They too had to have a gap otherwise you would have a faraday shield and nothing would 'get in'.

Steve

[Jerry]

Mylar is an insulator and can has zero metal content.

However you can coat it in metal and it can look really silvery then.

DF loop aerials have non ferous solid metal tubes around their windings.


used to see them on top of ships masts - They too had to have a gap otherwise you would have a faraday shield and nothing would 'get in'.

Steve

Survival blankets are conductive on one side and are suitable for coil shields. dfbowers covered it pretty well in his TGSL101 article which you can find here:

http://www.geotech1.com/forums/showthread.php?t=15710

Jerry

[der_fisherman]

Hi Dennis
Its not so much the difference between the LM308/TL071, more to the point its who manufactured them, I know this first hand because after building my TGLS I had problems with detection range which you may remember me posting on here, and I was doubting my build quality , but it was my LM308s that was at fault which was bought here in England, I swapped for TL071 which came from China and all worked to spec as has been posted on here.
I then bought LM308s from another supplier to see if i could get a bit better as we do, results, there was know noticeable difference between the two.
Im affraid that this is what we are up against which is a pain the ***.
Regards

I wonder if you got "forged" components?
I have heard of people buying accidently buying "Forged" processors and when they unpacked one, it was just a thick piece of copper bar......

Just because it has a famous name printed on it, does not mean that they actually made it. In fact, very unlikely indeed.....

I would advise you to drop the famous company an email, tell them that you may have bought components that a) carried their name that b) did not work and offer to send them the components for examination, also where you bought it (receipt).

You will probably get sent back a box containing many new good chips and a few other interesting ones as well as they don't want their name dragged through the mud......

You will also be helping them to track rogue companies.

Having an MD not work is one thing, but having medical equipment not work can kill people, let alone the financial losses involved for the manufacturer....

regards

Andy

[salih]

Hi salih:

Sorry, I misunderstood about the video. I understand it is not your MD now.

With your TGSL, after modifying the sensitivity, what happens if you turn the pot to max sensitivity? Do you hear any beeping of any kind?

Please do this:

1. Put a jumper across your RX coil leads (shorting the RX coil).

2. Measure the DC voltage at the output of each LM308 with a sensitive voltmeter using millivolt scale.

3. Remove the jumper from the RX coil leads.

4. Measure the AC voltage at the output of each LM308 with a good voltmeter that can measure up to 15 kHz.

Tell us the results.

Regards,

-SB

hello simonbaker
I can't do what you said, I do not have tools to know voltage and current. sorry
There are steps I followed, I want to let you know
1-Has changed all resistors (Please do not laugh)
2-I Shield RX and TX
Results:
*my MD Become more sensitive (26cm for coin)
*my MD Become not feel the rock (this is good)
when I Turn On my MD I hear Voice like ( beeping )
the Strange thing if RX and TX shield or not. I can't hear any noisy when I put max sensitivity
By the way I Use TL071 replacement to LM308N
sorry simonbaker I am weak in English.
Regards

[simonbaker]

I wonder if you got "forged" components?
I have heard of people buying accidently buying "Forged" processors and when they unpacked one, it was just a thick piece of copper bar......

Just because it has a famous name printed on it, does not mean that they actually made it. In fact, very unlikely indeed.....

I would advise you to drop the famous company an email, tell them that you may have bought components that a) carried their name that b) did not work and offer to send them the components for examination, also where you bought it (receipt).

You will probably get sent back a box containing many new good chips and a few other interesting ones as well as they don't want their name dragged through the mud......

You will also be helping them to track rogue companies.

Having an MD not work is one thing, but having medical equipment not work can kill people, let alone the financial losses involved for the manufacturer....

regards

Andy

I believe you're right.

I have a feeling that more often the parts are not "fake", but rather out-of-spec parts that are being dumped on hobbiests at low prices.

When I first looked for LM308 chips, I saw prices like $10 per chip -- I was bummed out, thought no way -- end of TGSL experimenting.

I eventually picked up a bunch of LM308s at about $.50 a piece from a typical on-line mail-order supplier aimed at hobbiests (probably). Nobody ever says parts are out-of-spec, but what do you think happens to precision parts that fail a test by a couple of millivolts? I don't doubt they end up in my parts box!

So you pays your money and takes your chances. Suppliers with higher prices that market to commercial businesses probably are safe to buy from.

On the other hand, understanding a circuit thoroughly may allow us to use slightly "idiosyncratic" parts by knowing how to measure and compensate for their peculiarities.

I agree it is aggravating when you spend hours trying to fix a circuit when some part is a dog.

That's why we never can get bored...

-SB

[Qiaozhi]

I can't do what you said, I do not have tools to know voltage and current. sorry

You are really making your life very difficult.
It is hard enough to debug a non-working detector without an oscilloscope, but if you don't even have a multimeter ... well ... I don't know what to say.

[simonbaker]

hello simonbaker
I can't do what you said, I do not have tools to know voltage and current. sorry
There are steps I followed, I want to let you know
1-Has changed all resistors (Please do not laugh)
2-I Shield RX and TX
Results:
*my MD Become more sensitive (26cm for coin)
*my MD Become not feel the rock (this is good)
when I Turn On my MD I hear Voice like ( beeping )
the Strange thing if RX and TX shield or not. I can't hear any noisy when I put max sensitivity
By the way I Use TL071 replacement to LM308N
sorry simonbaker I am weak in English.
Regards

Well, Ok. 26 cm is great, you're done.

Did you build the original TGS with the battery check? That may beep when you turn it on.

Why don't you check the wiring of your sensitivity pot and see if you have it wired backwards. Maybe you have min and max reversed -- no problem, just be aware how it works.

Can you post some photos so we can see your setup?

Regards,

-SB

[salih]

You are really making your life very difficult.
It is hard enough to debug a non-working detector without an oscilloscope, but if you don't even have a multimeter ... well ... I don't know what to say.

I am Not making my life difficult . My life already difficult , I worked so hard Without tools to make something very value to me (TGSL) .
Of course, with your advice I can succeed.
The bright side Now I can detect coin in 26cm.
I want to thank you and thank all the participants in (Geotech Forums).
Greetings

[der_fisherman]

I believe you're right.

I have a feeling that more often the parts are not "fake", but rather out-of-spec parts that are being dumped on hobbiests at low prices.

When I first looked for LM308 chips, I saw prices like $10 per chip -- I was bummed out, thought no way -- end of TGSL experimenting.

I eventually picked up a bunch of LM308s at about $.50 a piece from a typical on-line mail-order supplier aimed at hobbiests (probably). Nobody ever says parts are out-of-spec, but what do you think happens to precision parts that fail a test by a couple of millivolts? I don't doubt they end up in my parts box!

So you pays your money and takes your chances. Suppliers with higher prices that market to commercial businesses probably are safe to buy from.

On the other hand, understanding a circuit thoroughly may allow us to use slightly "idiosyncratic" parts by knowing how to measure and compensate for their peculiarities.

I agree it is aggravating when you spend hours trying to fix a circuit when some part is a dog.

That's why we never can get bored...

-SB

LOL!!

[satdaveuk]

duff parts

I remember years ago it wasnt uncommon to get resistors from known manufactures/suppliers to the radio/tv trade etc where they were sending out resistors with wrong colour codeing, what a pain in the *** that was, tryed to get into the habbit of checking each component where possible before installing, but to this day I still forget.
Another one to look out for is pin outs ID, This particular project uses mainly T092 packages, and that in no way tells you its EBC 123, there are 5-6 pin out combinations, and that is another reason why we are getting so many conflicting storys between say TL071/BF245. Note: you can purchase transistors with same part ID same package, but different pin outs.
Try contacting some of the suppliers and often even they dont know, so again its another pain in the ***.
The best way I found of working out pin out conections is first of all get you multimeter and find the Base which set on 20 mega ohms range, you will find continuety between base and emitter and base and collector one way very much like a diode reading, the polarity will depend on wether its a PNP or NPN, the emitter to collecter reading normally will read O/C on 20mega ohms setting.
So with this first simple test you will know if its PNP or NPN and you know your base conection.
To work out the collector/emitter conections I plug the transistor into the hfc socket on one of my multimeters and swap between the E-C leads until I get the most sensable reading which is normally the lower readings of the two.
If anyone here has any better ways of doing it please bring it on here because its a very important subject that far as I know has been discussed enough.
Hope this helps a little.
Regards

[Qiaozhi]

If anyone here has any better ways of doing it please bring it on here because its a very important subject that far as I know has been discussed enough.

I use a cheap multimeter, as shown below. It has the ability to test bipolar transistors and measure hfe.

[golfnut]

IGSL KIT - feedback

All - got my Silverdog IGSL-TGSL kit thru.

Positives
Very prompt delivery

Silverdog had written the resistor values on the packing strips which was handy.

Good quality Branded IC's like ST etc, some caps made by Wima - well respected brand

Pleased to see a little speaker in the kit too.

I tallyied the parts and it all was there to the letter.

Solid pcb, massively better than bodging something yourself.


Not sures
10k trim pots, 20k were supplied - should be ok though.

Cmos Ics loose in polythene bag - better chance of survival in antistatic foam, bag, or in ally foil wrap.

All 4u7 caps on the schematic are clearly markrd - Non Polarised Electrolytics
Supplied 4u7 caps are Polarised! (normal electolytics)?


I can look these up.
2N2907? Osillator transistor was metal can type - doesnt match silkscreen image - orientation?
BD140 pin out not known - could go either way?


All in all a good effort.

[der_fisherman]

Component values

I remember years ago it wasnt uncommon to get resistors from known manufactures/suppliers to the radio/tv trade etc where they were sending out resistors with wrong colour codeing, what a pain in the *** that was, tryed to get into the habbit of checking each component where possible before installing, but to this day I still forget.
Another one to look out for is pin outs ID, This particular project uses mainly T092 packages, and that in no way tells you its EBC 123, there are 5-6 pin out combinations, and that is another reason why we are getting so many conflicting storys between say TL071/BF245. Note: you can purchase transistors with same part ID same package, but different pin outs.
Try contacting some of the suppliers and often even they don't know, so again its another pain in the ***.
The best way I found of working out pin out connections is first of all get you multimeter and find the Base which set on 20 mega ohms range, you will find continuity between base and emitter and base and collector one way very much like a diode reading, the polarity will depend on whether its a PNP or NPN, the emitter to collecter reading normally will read O/C on 20mega ohms setting.
So with this first simple test you will know if its PNP or NPN and you know your base conection.
To work out the collector/emitter conections I plug the transistor into the hfc socket on one of my multimeters and swap between the E-C leads until I get the most sensable reading which is normally the lower readings of the two.
If anyone here has any better ways of doing it please bring it on here because its a very important subject that far as I know has been discussed enough.
Hope this helps a little.
Regards

I still check all transistor data sheets (still get it wrong sometimes ), but I check caps, inductances and resistors with the meter(s), its far too easy (forgetting for a moment wrongly marked devices as you correctly pointed out) to put a 4K7 where a 47K should be as red and orange are sometimes, especially under artificial light, difficult to sort out.

Due to an inadequate brain, I can almost never read a cap value and be certain I have it right......the cap meter is then the only way to go for me (never regretted making a Cap meter "addon" many years ago and buying one about 10 years ago with a larger range).......I have been too often wrong with values x10, x100 or even x1000 different to what I want......DUUUUHHHH!!

Regards

Andy

[silverdog]

All - got my Silverdog IGSL-TGSL kit thru.

Positives
Very prompt delivery

Silverdog had written the resistor values on the packing strips which was handy.

Good quality Branded IC's like ST etc, some caps made by Wima - well respected brand

Pleased to see a little speaker in the kit too.

I tallyied the parts and it all was there to the letter.

Solid pcb, massively better than bodging something yourself.


Not sures
10k trim pots, 20k were supplied - should be ok though.

Cmos Ics loose in polythene bag - better chance of survival in antistatic foam, bag, or in ally foil wrap.

All 4u7 caps on the schematic are clearly markrd - Non Polarised Electrolytics
Supplied 4u7 caps are Polarised! (normal electolytics)?


I can look these up.
2N2907? Osillator transistor was metal can type - doesnt match silkscreen image - orientation?
BD140 pin out not known - could go either way?


All in all a good effort.

Glad to hear it arrived safely

The 4u7 caps are arranged back to back to replace the Bipolar shown on the schematic, thats why C15 for example is shown on the pcb as C15a & Ca5b
The little lug on the 2N2907 is Emitter, the legs if you look are arranged like the pcb placement
Bd140 - with the writing facing you its ECB

good luck with your build

Silverdog