TESORO GOLDEN SABRE

[ivconic]

Whatever....i am not using fet part anymore. Of course base of 2N2907 goes via 47K to gnd. I get full 16vpp at collector.
With or without fet part i havent noticed any differences in behavior so far.
I do void fet part just for reason to save some space on pcb, no other special reason...

Other question here is interesting and possibly very important; threshold part? Original setup from first TGS posted here is without any trimmer just with fixed values. On one of my pcbs i included trimm for threshold and gained no benefit form it...
So at next pcbs i omitted it again.
Audio path is an issue here and must be reconsidered and modded. I tried many times and yet not satisfied..

[Max]

I look at Eldorado thread, schematic has 47K just like TGS. Is there another schematic?

Another possibility: try pot with fet, tune the coil voltage for max volts without distortion... Not easy for Tesoro because production environment, but easy for us! But if doesn't matter anyway... Only way to know for sure is use pot, test with very deep target barely detectable.

Regards,

-SB

Hi,
I think you're right... in Eldorado it's like TGS, I think I made a mistake following that old Leto's post here:

https://www.geotech1.com/thuntings/showthread.php?t=13145

Maybe the 4k7 one is from Inca ?

Anyway, there are 3:

- silver-bandido
- eldorado-tgs
- other with 4K7

Kind regards,
Max

Hi all.
zener diode reduce your amplitude.its correct.but this can help on disc scale.
because the maximum differential voltage on LF353 is 10v.more amplitude can destroy your
sinus wave after that 100pf(disc).and also after amplifying.so there you havent sinus voltage and this can affect on your disc scale.

best regards.
Naeem

[simonbaker]

Hi,
???
You omitted it, but short S and D terminals, right ?

That way base goes to GND by 47K.

It's an amplitude regulator... change transistor polarization to give steady output voltage.

Some Tesoro's oscillator haven't the fet stuff... others, like TGS, have it instead. The difference is small.

I think it was added to give extra long time stabiliy than in versions without it.

Also, when strong temperature changes happens the just transistor approach could give consistent variations at amplitude of TX.

In picture I report same stuff of an old thread about silversabre: on left it's silversabre-osc, on the right is eldorado-osc.

Note the difference from TGS: in eldorado seems there's a 4K7 instead of 47K and NO 330K resistor at S and D.

So, we have , at least, 3 different strategies by Tesoro in their MDs:
- silver-bandido, with no fet section
- tgs with fet 47K and 330K
- eldorado with fet 4K7 and no 330K

But which is the best ???

Kind regards,
Max

I look at Eldorado thread, schematic has 47K just like TGS. Is there another schematic?

Another possibility: try pot with fet, tune the coil voltage for max volts without distortion... Not easy for Tesoro because production environment, but easy for us! But if doesn't matter anyway... Only way to know for sure is use pot, test with very deep target barely detectable.

Regards,

-SB

[simonbaker]

Errr..
Looking at the schematic posted in gift pack, threshold part.
Instead of R43-100K and the trimmer connected to + and - which is perhaps the best option so I can adjust threshold manualy I have 348K resistor (330K on ivocnic's pcb) connected to +8V. I already asked for this, it should be working fine. Maybe audio level is going too low, and eventually Im loosing some depth.

Still not clear about your schematic -- Ivconic design without threshold trimmer pot has 330k to -5V not +8V as I see it. Then he has R44 33k resistor from inverting input to ground. Your schematic showed single R46 30k resistor from inverting input to ground. Can you fix schematic and show us what you are actually building? Those resistors do affect sensitivity for deep targets (not so much for shallow targets).

Regards,

-SB

[Fred]

Strange? I omitted whole fet part from my last few TGS's and it is working the same. Also get 16vpp the same as was in the past.
I think fet part with zener is just sort of "fuse" there and in normal conditions do not affect signal amplitude at all. It is inactive all the time. Fet is "opened" and actually 2N2907 base is connected via 47K to ground.

The Zener voltage had a significant impact on the oscillator frequency , just by changing from 3v3 to 4v7 and 5v6.
Fred.

[Max]

Strange? I omitted whole fet part from my last few TGS's and it is working the same. Also get 16vpp the same as was in the past.
I think fet part with zener is just sort of "fuse" there and in normal conditions do not affect signal amplitude at all. It is inactive all the time. Fet is "opened" and actually 2N2907 base is connected via 47K to ground.

Hi,
???
You omitted it, but short S and D terminals, right ?

That way base goes to GND by 47K.

It's an amplitude regulator... change transistor polarization to give steady output voltage.

Some Tesoro's oscillator haven't the fet stuff... others, like TGS, have it instead. The difference is small.

I think it was added to give extra long time stabiliy than in versions without it.

Also, when strong temperature changes happens the just transistor approach could give consistent variations at amplitude of TX.

In picture I report same stuff of an old thread about silversabre: on left it's silversabre-osc, on the right is eldorado-osc.

Note the difference from TGS: in eldorado seems there's a 4K7 instead of 47K and NO 330K resistor at S and D.

So, we have , at least, 3 different strategies by Tesoro in their MDs:
- silver-bandido, with no fet section
- tgs with fet 47K and 330K
- eldorado with fet 4K7 and no 330K

But which is the best ???

Kind regards,
Max

[Max]

Hi Eclipse,

It could be my scope, will double check once I am finished the new board I am building. I used a 4v3 zener diode. I am reading app. +7.8V and -6.3V. Using power supply set at 12V to power board.

Thanks,

Mike

Hi,
if you change (actually select) the fet at oscillator stage (amplitude control part) you'll get higher voltage there.

Usually I see it good at 14-14.5Vpp, but in some cases you'll get near twice the supply rail like in the ideal case -the famous 16Vpp-.

The original TGS was with TIS75... but I think , cause of tolerances of devices, any Tesoro TGS had little different amplitude of output signal... not really all running at 16Vpp.

The fet kind also impact on non-linearity, but much more the PNP transistor you use... low gain ones give a sharp bump on signal.

Kind regards,
Max

[eclipse]

Errr..
Looking at the schematic posted in gift pack, threshold part.
Instead of R43-100K and the trimmer connected to + and - which is perhaps the best option so I can adjust threshold manualy I have 348K resistor (330K on ivocnic's pcb) connected to +8V. I already asked for this, it should be working fine. Maybe audio level is going too low, and eventually Im loosing some depth.

[eclipse]

Hi SB,
I took ivconics board and redisigned it. RH audio for test, visual low batt,
monostable (all those blocks are manually connected but onboard).
Adding ground plane took out 1/2 of the jumpers, also some traces were optimized. Added 1K resistor and I made the 2x100K into one 220K.
All capacitors were replaced with other larger footprint (otherwise there is no space for them). Replaced for BF245.
Otherwise everything is the same as the schematic.

I think i have failure, maybe board mistake or pcb manifacturing deffect or both. I had problems with getting it work good, after all I trashed it for now, took all valued components out and these days I'll assemble new standard board. When I get it working good (with chatters'n stuff) I'll go back to see what's wrong with that design.
Regards

[simonbaker]

Sorry for the delay, im attaching now the eagle file. Its made with Eagle 5.
Don't remember free or professional version, if I did it with prof, there is a big chance that you won't be able to open it. Check for errors, use it as is
I found the problem causing that I was unable to null the coil properly.
And next thing in the menu: changing the phase shift between Rx and Tx signals seems almost impossible just using the method of moving the two coils. The thing is I am now able to adjust the amplitude having 5mV/Div on the scope and Its hard to see even the peaks in the voltage, less than 1mVpp for sure! How much exactly I don't know perhaps around 0.1-0.2Vpp.
BUT: I can't adjust phase in this case. I can do that measuring on the output of LF353, but this will automaticly disable the good ballance achieved!
So the dilemma now is ways to achive phase shifting, not using Rx and Tx:

1. Using metal pieces, What type: Al, Cu, Fe... Drawbacks of this method? I know it's used by DIY-ers not by famous manifacturers (mineleb, tesoro) this must have a reason.
2. Using different values of resistors in the Rx preamp part. I've seen circuits which you can change resistor's values in Rx part to achieve phase shift
3. Others??

Regards

Hi Eclipse -

My job is to go crazy over different versions of TGSL schematics...

I notice some differences in your schematic from others. You have R41, R42 4k7 resistors on outputs of T1018 comparators IC7. Ivconic PCB and many of his schematics don't have them. Are they on your PCB?

Also, your final op amp driving audio (IC8B) has different bias to inverting input, just a 30k resistor to ground. That is different from all schematics I've seen. Is that on your PCB also?

Otherwise, looks like Gift Pack schematic with 555 astable audio enhancement.

But if those differences on your PCB, maybe perform different from Ivconic's?

Regards,

-SB

[simonbaker]

Here you go SB Only mods I did to board was to add attachment points for the wiring to the pots.

Mike

Thanks! Looks like you use infamous "Gift Pack" circuitry.

Note: schematic and PCB not match exactly -- schematic shows two 4.7k resistors on outputs of LM393 (U106). However, not on PCB. Just one of those mysteries...I am only one who cares though...it works fine apparently...

-SB

[simonbaker]

Strange? I omitted whole fet part from my last few TGS's and it is working the same. Also get 16vpp the same as was in the past.
I think fet part with zener is just sort of "fuse" there and in normal conditions do not affect signal amplitude at all. It is inactive all the time. Fet is "opened" and actually 2N2907 base is connected via 47K to ground.

I always wondered if that JFet really helped performance. I feel purpose is to operate oscillator more in linear region of transistor for less distortion (with less voltage), but who cares about distortion? Your tests are the truth, must not matter much.

However, JFet definitely affects my oscillator voltage (makes it smaller compared to grounding 47k). Depends on JFet Vgss-cutoff though -- maybe yours is on all the time, so shorting not change anything! Might as well bypass it then!

Regards,

-SB

[ivconic]

Hi Max,

I was pulling my hair out when nulling the coil, every footstep downstairs was knocking it out Plan on sending my wife shopping when I get around to fine-tuning it!

Mike

Guess what? Today i got mad due impossibillity to null one coil!?
I spent all day trying to balance it without success. Finally i muss coil and stamped madly on it jumping and swearing. Than made another coil and again had a lot of problems to null that too?? Finally i recured the fact that i DO have scope now!! (poor me..... i totally forgot that recently got scope - used to work without it so long time).
So connected pin 7. of LF353 on scope and saw pretty ugly oscillogramm! Not a sinus, not a square...but something very strange!? After 15 minutes i discovered micro junction on brand new coil connector!?!?! Damn! Damn! Damn! I destroyed first coil and lost all day just for that! Damn local supplier!
So when junction removed, nulling was easilly performed just in 10 minutes....sheeeesh!!!
Today i learned another lesson! Huh...life is difficult from time to time!

[ivconic]

Yes, 12-13 with sens not at max is a good detector, find good stuff with it as is. If make better, icing on cake!

Oscillator voltage depends directly on zener voltage and Vgs-cutoff of JFet. (Right now I have 10v p-p.) More zener volts and/or more Vgs-cutoff = more oscillator voltage. You can get distortion though -- but does it matter? One way to increase voltage is put diodes such as LED in series with zener, make volt drop higher. Of course, proof is in field if makes deeper detection. Or substitute JFet with greater Vgs-cutoff.

Regards,

-SB

Strange? I omitted whole fet part from my last few TGS's and it is working the same. Also get 16vpp the same as was in the past.
I think fet part with zener is just sort of "fuse" there and in normal conditions do not affect signal amplitude at all. It is inactive all the time. Fet is "opened" and actually 2N2907 base is connected via 47K to ground.