TESORO GOLDEN SABRE

[junko]

I am a totally newbye in metaldetecting.
I read everything you write.A lot of thank at all the contributor.
I have mounted the golden sabre with PCB, I found a missing diode in pcb layout near to IC7 lm 308.
I have mounted all standard component eccept
Tis75---Bf245a
Lf442---Tl082
Coil DD255
Tx 5mH 24 OHM 100 turn awg 30
RX 5.5mH 25 OHM 110 turn awg30
Retuned TX +1000pf for obtain 15.1Khz to 14.6 Khz
Now i have a lot of problem with inteconnection cable.
I have put a capacitor for tuning rx in the search coil 15nF, i must connect another capacitor in the pcb side 1000pf for decrease a cable jittering.
I thinks my cable it's no good ( usb cable). I will try another solution.
Have you suggestions ?
I will try to rewind one new coil tx 110 rx 120.
For now poor result 18 cm 1 euro coil.
Sorry for my english .
Thank
Best Regards
Junko

[Hush]

O.K. I'll check it.
Thank you very much.
Regards!

[ivconic]

Sorry for delay. Personally i havent spoted significant differences in behavior, between J107 and BF245b,c in TGS design. It is not critical there.
More critical is choice of LM308. H version showed better stabillity(metal case). Even if you put plastic LM308, will not give you uncontrolled instabillity, dont worry. Even TL081 can work there descent. I think your problems are laying somewhere else, but where? If not arround coil, than must be arround LF353 and first comparator (LM393). You should check those twice, each component.
Regards!

[Hush]

Hello Max and Dirceu!

Max, thanks for an answer. I've found on some slovakian site BF245C isn't good for TGS so decided to change it with BF245A typ.Heh- now as I see
it is not very good solution.Haven't B typ, so I give up of BF245 at all. Can't
find TIS75, any J typ, so I'll try with 2N4392, and post results latter. Tnanks again for trying to help us!

Dirceu wish you a luck, and PLEASE send report!

Regards!

[DIRCEU]

Hi Nelson, Max, and others.

I have a big problems with TGSL too. Can't beleve the problem is with coil, just like Nelson, cose I've made 3 coils, different size,very carefuly and they works all the same-very bad.No, it can't be the coils.I think maybe those FETS BF 245 are not good for this project... somewhere Max and Porkluvr
wrote about this,but as I haven't scope, can't see whats really happening.
Ivconic's detector works from the first moment exelent, but he didn't use BF
but J107, and I think it is reason of his success (not only that, he is old fox, and he knows much about detectors).As I saw, some poeple used BF and
machine works good, but manufactures making components with some tolerances and you can't find components with same characteristics.That could be our problem, but who knows.I've made also TGS and TGSL- works the same, no differences.So, it must be some of those components on PCB
doesen't work properly.Oh, I am very tired of trying again, again and again...
Even Geo, master of detectors, have some problems with TGS, if I understend well.
Can't find those FETs, only similar I can find in market is 2N4392.Is it good enough for this project?
Ivconic, wish you to get well.
By friends, wish you all the best.

HI HUSH

I HAVE A FEW PROBLEMS TOO. NOW I DECIDED CHANGE BF's.
RECENTLY I ADQUIRED TIS 75. I WILL POST THE RESULTS.

REGARDS

DIRCEU

[nelson]

Ok Max. Tomorrow i ll get LM308 from a good guy that contact me.
Next time i ll try to null again my last coils.
Question: When you try to null coils at first try, do you have very poor distance detection. If this is rigth, i have notice that a 2 cms coin is detected at about 5 cms, so may be i nedd to do fine nulling to get correct deep values.
regards
Nelson

Hi,
the BF245 can be A,B or C type. Each series has slight different cutoff voltage range... and that could be your problem if devices do not switch off when they must do.

For example... the "A" version has cutoff at Vgs (max) = -2V.

Personally I've tested B and C versions on my TGS and TGSL... both types worked OK. The A version I don't remember well now... but think I've tested in some critical place there... and worked too as expected.

You can use J117 there and make your life easier or use also TIS75 if find any from old stuff... e.g. radio things or switch to some other fet model too.

No much difference but you have be sure your fets suits there e.g. about the channel type and cutoff voltages etc... that's really important check and you can made with scope watching at gate signal on one channel and drain/sounce sampled signal effect on the other channel.

Design of TGS is not critical about fets... could be other and more important problems to watch at... coils seem easy but aren't for many people here... at least at first. All tesoro's require good nulled coils to works nice... otherwise you'll waste your time with average detectors (as some of them are when you buy and with e.g. original coils).

PS: 2n4392 I think could be ok there... has VGSoff max of = -5V

Kind regards,
Max

[Max]

Hi Nelson, Max, and others.

I have a big problems with TGSL too. Can't beleve the problem is with coil, just like Nelson, cose I've made 3 coils, different size,very carefuly and they works all the same-very bad.No, it can't be the coils.I think maybe those FETS BF 245 are not good for this project... somewhere Max and Porkluvr
wrote about this,but as I haven't scope, can't see whats really happening.
Ivconic's detector works from the first moment exelent, but he didn't use BF
but J107, and I think it is reason of his success (not only that, he is old fox, and he knows much about detectors).As I saw, some poeple used BF and
machine works good, but manufactures making components with some tolerances and you can't find components with same characteristics.That could be our problem, but who knows.I've made also TGS and TGSL- works the same, no differences.So, it must be some of those components on PCB
doesen't work properly.Oh, I am very tired of trying again, again and again...
Even Geo, master of detectors, have some problems with TGS, if I understend well.
Can't find those FETs, only similar I can find in market is 2N4392.Is it good enough for this project?
Ivconic, wish you to get well.
By friends, wish you all the best.

Hi,
the BF245 can be A,B or C type. Each series has slight different cutoff voltage range... and that could be your problem if devices do not switch off when they must do.

For example... the "A" version has cutoff at Vgs (max) = -2V.

Personally I've tested B and C versions on my TGS and TGSL... both types worked OK. The A version I don't remember well now... but think I've tested in some critical place there... and worked too as expected.

You can use J117 there and make your life easier or use also TIS75 if find any from old stuff... e.g. radio things or switch to some other fet model too.

No much difference but you have be sure your fets suits there e.g. about the channel type and cutoff voltages etc... that's really important check and you can made with scope watching at gate signal on one channel and drain/sounce sampled signal effect on the other channel.

Design of TGS is not critical about fets... could be other and more important problems to watch at... coils seem easy but aren't for many people here... at least at first. All tesoro's require good nulled coils to works nice... otherwise you'll waste your time with average detectors (as some of them are when you buy and with e.g. original coils).

PS: 2n4392 I think could be ok there... has VGSoff max of = -5V

Kind regards,
Max

[Hush]

Hi Nelson, Max, and others.

I have a big problems with TGSL too. Can't beleve the problem is with coil, just like Nelson, cose I've made 3 coils, different size,very carefuly and they works all the same-very bad.No, it can't be the coils.I think maybe those FETS BF 245 are not good for this project... somewhere Max and Porkluvr
wrote about this,but as I haven't scope, can't see whats really happening.
Ivconic's detector works from the first moment exelent, but he didn't use BF
but J107, and I think it is reason of his success (not only that, he is old fox, and he knows much about detectors).As I saw, some poeple used BF and
machine works good, but manufactures making components with some tolerances and you can't find components with same characteristics.That could be our problem, but who knows.I've made also TGS and TGSL- works the same, no differences.So, it must be some of those components on PCB
doesen't work properly.Oh, I am very tired of trying again, again and again...
Even Geo, master of detectors, have some problems with TGS, if I understend well.
Can't find those FETs, only similar I can find in market is 2N4392.Is it good enough for this project?
Ivconic, wish you to get well.
By friends, wish you all the best.

[nelson]

Thanks Max.
I know no one can belive me when i said that i can get the correct coil working, but i can tell that i have done it with correct wire, numbers of turns, correct size form, etc. and nothing. The best coil i made it has less turns and is working at 19.2 Khz.
The other coils works, but performance is bad. My 19.2 Khz coil, was very easiñy nulling the others did not.
So is the reason i think i must have a problem with the receiver part of my TGS. Yesterday i lots of time cjeking components numbers on PCB and by now i found nothing.
About coils mH, do you know if the values posted where measured by each experimenter here or where obtained from a factory sheet?
Has always, many thanks for taking the time to help me.
Best regards to all
Nelson

Hi,
change about nothing... use one of the 2 values...

This isn't your problem.

Your coil is wrong if you get such higher frequency... as I told you before... maybe it's wire... or number of turns... or you made wrong tightening of wounds... leaving turns too open etc etc.

Also varnish tickness is important cause of the surface capacitance increase or decrease you can get.

I suggest you find sure 30AWG and made it again using provided data.

The bare wire will be exactly 0.25mm not other things (the varnished wire diameter goes from 0.27 to 0.28mm).

Wire is critical if you use Ivconics numbers on turns... so stay close as possible... otherwise you'll get another wrong coil.

Then nulling is most important phase in all this stuff... and require extra care... it's not easy thing... but you can do. Don't worry.

Kind regards,
Max

[Max]

Hi, i think i found my problem with coils for my TGS. I noticed that a 5 PF cap is on pcb, very close to RX stage. (See the drawing), btw pins 6 and 7 of LF353. But on the schematic there is a 10 PF cap. So can this change my RX frequency?
I m using a 5 PDF cap instead of the 10 PF cap show on the schematics.
Please give me a detail explanation, cause my best performance for TGS is on 19, 2 Khz.
Regards
Nelson

Hi,
change about nothing... use one of the 2 values...

This isn't your problem.

Your coil is wrong if you get such higher frequency... as I told you before... maybe it's wire... or number of turns... or you made wrong tightening of wounds... leaving turns too open etc etc.

Also varnish tickness is important cause of the surface capacitance increase or decrease you can get.

I suggest you find sure 30AWG and made it again using provided data.

The bare wire will be exactly 0.25mm not other things (the varnished wire diameter goes from 0.27 to 0.28mm).

Wire is critical if you use Ivconics numbers on turns... so stay close as possible... otherwise you'll get another wrong coil.

Then nulling is most important phase in all this stuff... and require extra care... it's not easy thing... but you can do. Don't worry.

Kind regards,
Max

[tiktak]

Hi,

Hi,
Nelson.
Unfortunatly I cant help you with detail exponation,you should ask Max or Ivconic for such.I am only entusisast!
But this 5pF cap is not your probleme!First this cap were 5pf and then the value were changed for better performance.But I havent notice any differance when changed this on my PCB.
I am afraid that your probleme is different.

[nelson]

Hi, i think i found my problem with coils for my TGS. I noticed that a 5 PF cap is on pcb, very close to RX stage. (See the drawing), btw pins 6 and 7 of LF353. But on the schematic there is a 10 PF cap. So can this change my RX frequency?
I m using a 5 PDF cap instead of the 10 PF cap show on the schematics.
Please give me a detail explanation, cause my best performance for TGS is on 19, 2 Khz.
Regards
Nelson

Hi,
Nelson.
As I told you I never measure the frequency on my TGS.I just have experimentated a lot and with help from Max and Ivconic found the best nulling for me.
I think that the small diferances in some parts make a diferance,so every TGS is for itself no metter that we are using same elements.
So I sugest you try wind another DD with TX=100 and RX=105 and null afther firs OP!LF 353 pin 7.
Try.

[tiktak]

Hi

Hi,
Nelson.
As I told you I never measure the frequency on my TGS.I just have experimentated a lot and with help from Max and Ivconic found the best nulling for me.
I think that the small diferances in some parts make a diferance,so every TGS is for itself no metter that we are using same elements.
So I sugest you try wind another DD with TX=100 and RX=105 and null afther firs OP!LF 353 pin 7.
Try.

[nelson]

HI TIKTAK.
WELL I HAVE 90 AND 95 TURNS, RESISTANCE 24,2 AND 24,9 OHMS
INDUCTANCE 5.25 AND 5.65 mH, FREQUENCY 15,1 KHZ
IF I MEASURED INDUCTANCE WITH MORE PROFESIONAL METER I GET 8.25 AND 8.65 mH. SO WHATS WRONG?
COULD BE THIS A PROBLEM WITH SOME TUNING CAPS ON PCB?
MY BEST COIL IS MESURING 4.24 AND 5.2 mH, RESISTANCE AROUND 18 OHMS, FREQUENCY 19.1 KHZ
REGARDS
NELSON

Hi,
Nelson.
I think that you use wrong data!
For DD 28cm TX=100 RX=105 w!

My TGS is working realy good now!I have found my first coin!And haven't even measure the working frequency!

I think that you should try nulling the coil from LF353 pin 7!
This way I finaly null my coil more than workable!/you null now using L2 end and start right?/

p.s.Happy new year

[Max]

Hi Ivconic and all TGS fanatics.
Well i just whant to tell and share my expirencies and problems found with TGS coil.
My best coil it measures 4.8 mH and 5.7 mH, resistance btw 17 and 19 ohms respectively, for a 28 cms coil form, wire is 30awg or 0,25mm.
I measure the frequency and this reads 19.2 Khz
I tried another 28 cms coil, with 120 and 125 turns, resistance was around 34 ohms, and inductance was over 10 mH
Then my next coils were 28 cms form, 24.9 and 24.2 ohms, inductance 5.65 and 5.25 mH. Numbers of turns 90 and 95. This were the closest values i got, the frequency on the coil 15.1 Khz. Detection very poor.
Now i have more questions than before, cause i can get the correct deep results.
On this last coil i made, i measured inductance with ordinary multimeter, then i measured with a good inductance meter and this reads values around 8 and 8.9 mH. This also means to me that if i whant to get around correct values i should remove more turns, and this less than 90 and 95 turns.
So finally i belive that i must correct somo caps on the circuit.
I hope the experts on TGS can give me orientation on this, cause i m very confused now.
Ivconic, what inductance meter did you use?
120 turns give me more resistance than the one you posted.
I know i have errors here but can´t figure out what are those.
Regards and thanks for your support.
Nelson

Try to get from 14 to 15Khz... better if from 14.4 to 14.8 Khz... if so and you null well the coil you go well depth with TGS.

Look also for optimum GEB setting ...otherwise you'll get many falses.

My TGS works so great now that I cannot post here about

People don't wanna belive me... think I'm a joker or something if I post.

Kind regards,
Max