TESORO GOLDEN SABRE

[ivconic]

You should read posts more carefully. I explained how made mistake and soldered LM308H (same as yours-metalic case) wrong way, considering pin 1. under notch. When switched ON it started screaming...! I was confused...
Later when corrected and resoldered right way (pin 8. under notch) it started working good. No harm done. Nothing burned ...thanks to God!
But you dont need to check if it is gonna burn or not !
Just put it right way - pin 8. under notch.
About capacitors....i dont know. I put components respecting component placement on pcb you posted here...No mistakes, so far as i am concerned..
Regards!

P.S.
Inform us when you finished...

[ivconic]

But...if you insist; here it is!

[Max]

If you look at the schematic posted earlier, where I asked you to disconnect pin 1 of U106A, there is no 1M resistor. BUT - if I look again at the original schematic, then there is a 1M resistor, but it is connected by a dotted line with some words that say "To check this!". Must be an old schematic.

Glad you have fixed the problem.


Looks like you really had 15mV after all ...


I plan to do some experiments soon to look more closely at this question. At this time, however, I still think that nulling the residual voltage to the nth degree is not necessary.

Hi,
no... i nulled it at 5.5mVpp using scope... the multimeter reads also 0.0mV but that's another story... I've checked at 0.1mV indication of multimeter and read about 20mVpp so I concluded that 0.1mV on multimeter are about 15mVpp more on scope!

So guessed about tesoro guys and how they null cause of your previous post... if they actually use in the test pattern just a digital multimeter to do so... maybe they look at transition between 0.0 and 0.1mV indication as reference... thus producing 15-20mVpp out-nulled coils.

I really don't know... what they use or is there are everything same procedures making e.g. a concentric coplanar coil or a DD or oval... but maybe someone there use really a multimeter to speed up things instead of watching at scope... or some differential circuit fully analog ... maybe with center zero!

Problem is not instrument used but that people must know what are doing... and they of course know everything about coils... and how to make mass production of them fast.

Anyway the fact that building another coil , with same specs , I get now just 10Hz difference from Ivconic and just about 0.5mVpp difference in null comparing with first smae type coil means that you can replicate also so close the coil yourself to better looking at these misteries if you want.

Best regards,
Max

[Qiaozhi]

Ehm! No...i am looking for audio simillar to CZ5; a bit longer lasting,changing pitch,decayed and as you explained earlier in that post i quoted above..
Should not been a huge problem...?
Regards

OK - the speech processor wouldn't be any use to you anyway. I found the circuit and it's basically a method of doing soft limiting, which can be used to boost weak signals without blowing your eardrums apart with the loud ones. I guess you are really looking for a simple VCO solution?

[ivconic]

Hi,

no... i nulled it at 5.5mVpp using scope... the multimeter reads also 0.0mV but that's another story... I've checked at 0.1mV indication of multimeter and read about 20mVpp so I concluded that 0.1mV on multimeter are about 15mVpp more on scope!

So guessed about tesoro guys and how they null cause of your previous post... if they actually use in the test pattern just a digital multimeter to do so... maybe they look at transition between 0.0 and 0.1mV indication as reference... thus producing 15-20mVpp out-nulled coils.

I really don't know... what they use or is there are everything same procedures making e.g. a concentric coplanar coil or a DD or oval... but maybe someone there use really a multimeter to speed up things instead of watching at scope... or some differential circuit fully analog ... maybe with center zero!

Problem is not instrument used but that people must know what are doing... and they of course know everything about coils... and how to make mass production of them fast.

Anyway the fact that building another coil , with same specs , I get now just 10Hz difference from Ivconic and just about 0.5mVpp difference in null comparing with first smae type coil means that you can replicate also so close the coil yourself to better looking at these misteries if you want.

Best regards,
Max

Uh! You gave me worries now! Respecting first lines of your post; with or without 15nF capacitor? (i guess with...) In that case my coils have larger residual voltage than i planned! Shame!

The rest; yes i always wandered how the heck they ballanced coils in massive production? Do they have some "special" instrument?
I was thinking to make something simillar. Esteban posted once some schematic...i looked at it and it is not bad at all. But...i was thinking to make more accurate op-amp based milivoltmeter (ultra high input impendance) and separate tunable oscillator with clear sinus at output...
Problem is; i want to keep it as simple as possible, so must use analogue VU scale....very hard to obtain good one with high resolution...
Also another problem is ....question; how to maintain that meter to be linear due eventual jumps,jitters,nonlinearities which may occur on frequencies like 10-15kHz..?

Considering scale..monitoring...i am not sure how good are those lcd indicators based on ICL7107/06...?
I can simply take that part from some cheap multimeter and include in my design....but this probably return us to the begining of this story;
what error level should be expected from those?
Huh!

[Max]

I'll leave power mod as last to do here.
First to do first! Stabillity issue...
But you mentioned replacing one capacitor with few parallel... So i am thinking; we have 220nF at TGS oscillator. We can easuly replace it with 3 parallel of 68nF and forth of 22nF. It will make 226nF..Cool! But what benefits we do have from those, except less current as you said?
Let's explore this more; when oscillator runs better? With one compact or few parallel? This must be scoped to be sure. Second; which type are best suited to put in oscillator? I am using P.P. capacitors mostly..
Also which transistor? I am using 2N2907 although BC557 tested and havent noticed significant differences...
This subject already explored in the past, but no harm if we elaborate it further..
Imoprtant question; how to replace stabilisation with fet in oscillator. Using termistors is bad idea, more obsolete than fet setup. Also i havent noticed jitters in TGS oscillator but that doesnt mean it is perfect. To be honest i havent payed to much attention on its stabillity at all. First time i made TGS just checked it for 2 hours on eventual jitters, and when i saw there are no significant jitters, i left it as it is.
One thing is not clear to me is zener diode. 4V3 is suggested, i put 4V3 and later 4V7 - havent saw any differences too?! So what's point with zener here after all? I think to put 3V9 or 5V1...or even 6V8 to see if any changes?
Should i?
And there are so many other question to be answered....but i am not in a hurry...winter is coming, we have plenty of time...
Regards!

Hi,
oscillator stability is not a big issue on TGS... it's relatively stable. Due to the low power involved and that it has also an amplitude stabilization network by zener + fet... it's really good for this design.

Improving the power would be nice to see till when it could give problems on soil... and using Geo's approach one could e.g. use more power in more easy soil (no or few minerals) and reduce it to standard TGS power on worse (infested or hi-mineralized) soil.

I think that would be good using something like a BD137 with proper driver to get much more power at coil... or using an osc like in the bulgarian designs with the lm317 to limit power.

I think we can easy double the power without problems... but 3 times or more could be impossible on most soils.

The feedback network can be redesigned to be controlled by an op amp... instead of zener+fet params... then feeding the LM317... to avoid open-chain control (direct) of the power (and so increase stability by gain of factor of the gain of amplifier).

Best regards,
Max

[ivconic]

OK - the speech processor wouldn't be any use to you anyway. I found the circuit and it's basically a method of doing soft limiting, which can be used to boost weak signals without blowing your eardrums apart with the loud ones. I guess you are really looking for a simple VCO solution?

Yes! Although not figured proper way how to connect one on existing TGS setup?

[Max]

Uh! You gave me worries now! Respecting first lines of your post; with or without 15nF capacitor? (i guess with...) In that case my coils have larger residual voltage than i planned! Shame!

The rest; yes i always wandered how the heck they ballanced coils in massive production? Do they have some "special" instrument?
I was thinking to make something simillar. Esteban posted once some schematic...i looked at it and it is not bad at all. But...i was thinking to make more accurate op-amp based milivoltmeter (ultra high input impendance) and separate tunable oscillator with clear sinus at output...
Problem is; i want to keep it as simple as possible, so must use analogue VU scale....very hard to obtain good one with high resolution...
Also another problem is ....question; how to maintain that meter to be linear due eventual jumps,jitters,nonlinearities which may occur on frequencies like 10-15kHz..?

Considering scale..monitoring...i am not sure how good are those lcd indicators based on ICL7107/06...?
I can simply take that part from some cheap multimeter and include in my design....but this probably return us to the begining of this story;
what error level should be expected from those?
Huh!

Hi,
yes... I've used 15nF cap and 1k resistor parallel (as in point 4.)... and problem is related to planes of coils... and overlaps...

I think that if they use an analog meter is something similar you can find here mixed with other stuf:

http://members.aol.com/omlcgm/radiometer/radiometer.htm

The link was posted by Sean Goddard somewhere...before.

You can also find some other useful info.

I have also some schematics (but where ???) of op. amp. driven analog ac meters (using moving coil instruments) for bf... so good till 20Khz. That would be very nice in that kind of stuff.

Personally I think that an analog meter would be always better doing such a measure... instead of using a digital something.

Also I'll made my instrument with linear meter with central zero (e.g. +/-100uA instrument) and a cascade of resistance to set the dinamic gain to have end-scale e.g. 20mV, 10mV, 5mV, 1mV , 0.1mV

That way one could set with rotating switch the gain during the nulling using one hand... and with the other moving the coils... that's somehow similar rotating the vertical knob of scope.

Best regards,
Max

[ivconic]

I do have idea already....
Glad to see that you suggested scale...only have to find good one.
I'll prepare schematic of "coil balancer" and post here later...
Actuallly i dont need to include separate oscillator!?
Best way is to suite exact coil to exact device and only way to do so is to use origin oscillator from device, when balancing coil...
So i'll consider only RX part...

Regards!

[Max]

I attach here the pcb with errors that Max sent here. I have checkthe 10pF... the 1M and one diode that there is at the schematic but no at the pcb. Tell me if are correct.
I have 2 LM308 with metallic case. Where is the ledge??? Ivconic said that it is on pin1......... i looked at datasheet and shows it at pin8. Who is the right.... the shop had only 2 pieces so i dont like to burn it.
Regards

Hi Geo,
look at green oval... there is the diode (labeled as D12 in TGSL schematic by Ivconic) : you have to put the 1M resistor there in parallel to diode... but using the switch in series... to connect/disconnect it.

Be aware of it if you notice too erratic noise without. If there isn't too much internal noise you can use it gaining better audio for far targets and weak signals.

About the cap... yes... 5 or 10pF. You can use 5pF without problems; circuit works also with 10pF there... me cannot see or ear differences by that.

Looking at other schematics by Tesoro now actually I think it was 5pF and not 10pF. But maybe TGS is different from them... who knows.

Important is that works with both.

Best regards,
Max

[Max]

I do have idea already....
Glad to see that you suggested scale...only have to find good one.
I'll prepare schematic of "coil balancer" and post here later...
Actuallly i dont need to include separate oscillator!?
Best way is to suite exact coil to exact device and only way to do so is to use origin oscillator from device, when balancing coil...
So i'll consider only RX part...

Regards!

Hi,
yes you could add a general purpose oscillator... with variable freq. from e.g. 1KHz to 20KHz and variable amplitude of 1Vpp to e.g. 10Vpp... I think the easy and best thing could be :
- a bf oscillator Wien type
- some ic like ICL8038

+ some power stage (class A transistor amplifier)

That way you have really good shaped sinus and stable frequency on the BF region... and also really few distortion from end stage.

Maybe the ICL8038 could drive coil directly... using some small impedance matching component... so saving also the work to make output stage.... or one could use also some old small function generator to do the same... maybe just dismantling board and enclose everything in a single box (osc+meter stuff).

The advantage of using an old signal generator (like e.g. some 70's HP I have in mind) is that you could also pump a sweeped signal to trace self resonance of coil... by meter !

But it will become more complex of course.

Best regards,
Max

[porkluvr]

too much Q?

Ivconic-
False targets could be caused by instability of the DISC opamp.
The high value of feedback along with input capacitance can cause ringing.
It will be worse if you have a Hi-Q coil.

I had a longer spiel typed up to explain my screen shot image,
but my computer crashed while editing the photo. I hadn't saved the text. Sooo, I'll just post the before and after photo and let you determine if you can use the info.

Adding a capacitor across the 100k resistor makes the TGS DISC control similar to the Bandito's topology.

[ivconic]

Thanks Porkluvr! I have good will to experiment more on this...

[Geo]

Hi Porkluvr. Can you simulate the circuit with Tx transistor the 2N2219 and Vosc=18V. I want to see how much bigger will be the Tx signal and if the signal phase is the same.
Regards

[Geo]

No Geo! Beware! I sad that made MISTAKE considering pin 1. under notch...
It is pin 8. under notch not pin1. !
Yes there are 4k7 resistors in chopper, not 47k as showed in schematic.
There is also 2k2 instead 33k....
about 470k in battery test....i put 470k,it is working...
1M resistor goes parallel to diode...only if you want to boost audio. For now do not put it.Leave as it is...

Ok Ivconic.
In the schematic there is a diode at one LM308 that there is not on the pcb (pcb shows only one LM308 with diode parallel to the feedback resistor). Do you connected it??
I finished the pcb with the components. Now i must connect the potentiometers and switches and it is OK. Maybe tomorrow .... today i am busy.
Regards