TESORO GOLDEN SABRE

[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.

[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

[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

[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.

[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

[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

[Naeem]

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

[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/s...ad.php?t=13145

Maybe the 4k7 one is from Inca ?

Anyway, there are 3:

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

Kind regards,
Max

[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..

[simonbaker]

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..

Regarding audio: can you remove three capacitors after comparators (i.e. C24, C25, C26) and tell us what the audio sounds like? It will probably increase chatter, but will reveal some clues.

Regards,

-SB

[ivconic]

I did that long time ago, so as experimented with different values - no benefits.
Removing C24 and C25 seems does not change anything in audio, but removing C26 do affects it to become worse.
Heck is somewhere else. I guessed once and will repeat again; all the signal path is issue here. Possibly some low amplification. Guess they (at Tesoro) wanted to supress chatters also so whole design is adapted in that manner.
What we need is sort of "linear" amplification, one stage more, than some MPSA13 or whatever at the end. But signal at last LM358 is pretty awkward to be easy played with it. If you followed this thread from a start ,you probably remember dozen small modds i tried already, sheeesh, nothing helped much! Few times i used signal to switch something to produce audio, and it worked but not "linear". Audio was independent of target preferences. That is not what i want. I want audio to be directly dependant of a target, so you can hear depth and size. Tough...very tough.

[Max]

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..

Hi,
I see...

Yesterday I tried with a BC557 instead of 2N2907... and no fet on my TGSL board.

Result was 15Vpp signal but distorted at top... who knows why ???

The BC557 I used was 250 as HFE so about an average pnp one.

Using the fet (a BF245B) the voltage drops with that stuff at 14.4Vpp BUT is much more linear and almost near to perfect sinus wave.

As reported before, the FET serves much to mantain amplitude stabilization BUT also linearity of the sinus wave.

Is linearity important ? Well... I saw also distorted signal giving good performances on air but not always, and on soil linearity I think is important cause of geb/disc implications.

I also know that just transistor osc is fine (I have bandidoII running fine) but components are different at it... look at picture, with that values I really get perfect sinus there.

I think that's maybe a good idea refine components at oscillator of TGS if wanna pull-out the fet and have good linearity.

Kind regards,
Max

[ivconic]

I think you have right, Max!
I would rather adjust resistors there than to keep fet stage.
I was thinking to put trimmers instead base and emitter resistors and to adjust those using scope.
It was my idea from long time ago...i am just to lazy to do things faster than usually do...

Already adapted pcb draw, but dont have time to make it right now.Will be ready in a week or two...

[Max]

I think you have right, Max!
I would rather adjust resistors there than to keep fet stage.
I was thinking to put trimmers instead base and emitter resistors and to adjust those using scope.
It was my idea from long time ago...i am just to lazy to do things faster than usually do...

Already adapted pcb draw, but dont have time to make it right now.Will be ready in a week or two...

Hi,
yes, I think that's the good way to keep everything powerful and stable, with good linearity of sinus.

The colpitts are easy but when doing at these levels of tuning is better tune also that stuff.

Kind regards,
Max

[ivconic]

I am also waiting some more ideas to occur, to adapt this pcb further, so once i make it, i want to change few more things than just TX amplitude and shape....
I done 28 TGSL's so far....kind a tired of repeating same old thing again and again....
So next MUST be pretty different.
Sooner or later i will face KT315's oftenly repeated attitude and remarks about "old and obsolete" stuff. Although i dont agree with it at all. But KT315 is right at some point, we must do something major at TGSL...