TESORO GOLDEN SABRE

[Max]

Max i havent noticed any changes in behavior; with or without 10 K parallel to disc pot??? When it echoing beeps...it is doing that with and without 10k.
Also al other functions remained the same with and without 10K...It is not big deal, i'll put it again...But havent seen any changes....better or worse???

Hi,
I think that you probably have some other and bigger problem that mask the positive effects of having it.

That's why you cannot see advantages... or maybe is just simulator that make us crazy now...

I told you I have dumped oscillations even with notch pot there ! that's strange thing for real: also for me having it or not is the same !

Maybe the LF353 is inaccurate ? Who knows... ?

What I know is that simulator tell me that I need the damn pot but then I see dumped oscillations on the "real" scope.

I guess the LF353 model that LTspice uses for simulation is too good to be real !

Best regards,
Max

[Max]

"...ONLY if there is already really rare and occasional noise..."

It seems there are some??? Fact that all bad things returned when 1M is present tell me that actually problem is not solved yet for real...
I am wandering what should be proper measuring points here on this TGS?
Can we establish those points and later scoping those we can eliminate part by part of device from further suspicion....With this method would be easy to locate problem and solve it.

I think that good points are:

- collector of transistor at osc
- output of preamp (pin 7 353)
- output of "disc" amplifier (pin 1 353)
- geb syncro signal (pin 7 of 393)
- signal after 20K resistors (drain -or source- of that fets)
- output of first 2 integrators
- output of 308s
- output of comparators

But seems hard work trace them all...

What do you think ?

Best regards,
Max

[ivconic]

Max i havent noticed any changes in behavior; with or without 10 K parallel to disc pot??? When it echoing beeps...it is doing that with and without 10k.
Also al other functions remained the same with and without 10K...It is not big deal, i'll put it again...But havent seen any changes....better or worse???

[Max]

"...otherwise it's a real boomerang..."
Most proper term for it!!!
Now when TGSL solved and working really good, if i add that resistor, i'll return this on the begining of problem...!?

yes ... exactly what I felt when tryed the ST's TL071s there and found no bleeping anymore... then I switched the resistor to be there... and wow... it looked like a crazy horse again !

Damn thing !

Not to say what happens when I put the fake LM308s... it really sings and I have to run away from the lab !

Real boomerang if things aren't quiet... I suggest we put apart that mod till we solve all the "noise" issue.

Then after we (maybe) could rediscover that 1M resistor!

Kind regards,
Max

[ivconic]

"...ONLY if there is already really rare and occasional noise..."

It seems there are some??? Fact that all bad things returned when 1M is present tell me that actually problem is not solved yet for real...
I am wandering what should be proper measuring points here on this TGS?
Can we establish those points and later scoping those we can eliminate part by part of device from further suspicion....With this method would be easy to locate problem and solve it.

[Max]

"..The funny thing is that disc works pretty good... and it cannot detect an hammer at 1cm in disc mode! .."
Same here! That is most funny, not only disc but geb also!?
Actually i stuck to damn pi 1. of LF353! Is it important to examine it after all?
Yes it si square ??? Yesterday was as you saw in shot, today with good cap from 100 to 330pf is square??? Differences between setup with 100pF and 330pf are only in purity of o.gramm not in shape!? Shape remains the very same from 150pF up to 330pF....
Today i'll replace LF353 with TL082,TL072,TL062 and simillars to compare...
About intermodulation...yes i think that too, but how to locate source of it?
When i solve that, automatically i will have chance to aplify audio more without risking of appearing false echoed beeps any more...
Now problem is completely "solved" with 18 and more ohms at the output...

Hi,
have you used the 10K resistor parallel to 100K pot of disc... cause I've made same simulations of porkluvr and results are the same... look.

I think you need it.

1. is the output at pin1 of 353 with the 10K (notch pot)
2. is the output at pin1 of 353 without the above pot...

Seems clear...

my problem is that I have the superimposed sinus WITH the notch pot there... that really puzzle me much.

Kind regards,
Max

[ivconic]

"...otherwise it's a real boomerang..."
Most proper term for it!!!
Now when TGSL solved and working really good, if i add that resistor, i'll return this on the begining of problem...!?

[Max]

Max, GEo, ApBerg ...can you attach some 8 ohm speaker to your devices, turn Sense to maximum, Disc to minimum and test it on coin? Try to approach to coil with coin slowly just to start weak detection. Than remove coin slowly. Let's see is it gonna stop or continue with beeps...?
Also can you scope pin 1. of LF 353 and post shots here?
I am persistent on this. I will continue experimenting until whole thing become clear to me...

It stops on mine.

[ivconic]

"..The funny thing is that disc works pretty good... and it cannot detect an hammer at 1cm in disc mode! .."
Same here! That is most funny, not only disc but geb also!?
Actually i stuck to damn pi 1. of LF353! Is it important to examine it after all?
Yes it si square ??? Yesterday was as you saw in shot, today with good cap from 100 to 330pf is square??? Differences between setup with 100pF and 330pf are only in purity of o.gramm not in shape!? Shape remains the very same from 150pF up to 330pF....
Today i'll replace LF353 with TL082,TL072,TL062 and simillars to compare...
About intermodulation...yes i think that too, but how to locate source of it?
When i solve that, automatically i will have chance to aplify audio more without risking of appearing false echoed beeps any more...
Now problem is completely "solved" with 18 and more ohms at the output...

[Max]

Hi,
here is the bandidoII part I mean... I remember that same problem happened in bandidoII : 8ohm speaker = bad, just good an apple computer 16ohm speaker with it.

So, of course, KT315 is right on mod... he followed Tesoro's rules ! so if you have to launch around rotten tomatoes... you have to point Arizona first ...

I'm joking now. Of course it works... and at Tesoro they made great designs!

but that will work ONLY if there is already really rare and occasional noise... otherwise it's a real boomerang.

Kind regards,
Max

[Max]

Max, GEo, ApBerg ...can you attach some 8 ohm speaker to your devices, turn Sense to maximum, Disc to minimum and test it on coin? Try to approach to coil with coin slowly just to start weak detection. Than remove coin slowly. Let's see is it gonna stop or continue with beeps...?
Also can you scope pin 1. of LF 353 and post shots here?
I am persistent on this. I will continue experimenting until whole thing become clear to me...

Hi,
my yesterday scope signal was with an 8ohm speaker already there.
Yes I noticed too... 8ohm increase problems cause maybe more current drawn by output stage... that thing will cause small transients on supply rail that enter then the signal path and produce false signal cause all op amps. reside on the same line... they don't have e.g. separate decoupling and the like you can see in other circuits (often a 10-22ohm resistor + some 22-100uF capacitor at supply rails of ics).

The transients could also create some low frequency oscillation that intermodulate with useful signal... thus giving unpredictable behaviour.

I think that problem could be avoided using some optocoupler instead of transformer...

Best regards,
Max

[Max]

And here is what i gainedd with good capactior...But i had to put 330pF to streighten up signal. When 100pf is on the place oscilogramm is still "broken" ...

Hi,
the 1M resistor is also in BandidoII schematic by default... it works cool when there is few erratic noise around... otherwise better avoid it at all.

The signal I see is with 330pf instead of 100pf ? Seems a square wave now !

I've tested my cap and it's ok... I've changed also it and all is the same... if I pull-out the lf353 I can see after the 100pf cap a perfect sinus signal like the one of Ap.Berg... but then when I mount LF353 it distorce the signal and I got the parabolic one with the damped oscillations.

So problem is at op. amp. inputs !

If I put a TLC2262 there instead of LF353 I got a near-to-sinusoidal wave... but different and with much less dumped superimposed signal.

TL072 there works exactly the same of LF353: signal is distorted.

The funny thing is that disc works pretty good... and it cannot detect an hammer at 1cm in disc mode!

So what's the story with LF353 ?

My actual part is LF353N from National, original part made in the 90's.

Any idea ?

Best regards,
Max

[ivconic]

Max, GEo, ApBerg ...can you attach some 8 ohm speaker to your devices, turn Sense to maximum, Disc to minimum and test it on coin? Try to approach to coil with coin slowly just to start weak detection. Than remove coin slowly. Let's see is it gonna stop or continue with beeps...?
Also can you scope pin 1. of LF 353 and post shots here?
I am persistent on this. I will continue experimenting until whole thing become clear to me...

[ivconic]

Experimented with values from 100pF to 330 pF. More i raise capcitance - the better oscilogramm, up to 330pF..
Except changing oscilogramm i havent noticed any other changes in TGS behavior!??
One more thing i noticed; i used 8ohm speaker at output. Audio was loud and clear but with ocassional false signals - beeps...
I added 10ohm resistor in serie with speaker (8+10=1 and no more false signals and beeps. Depth, sensitivity and GEB remained same - perfect! Only thing changed is audio level. Now audio is not loud but noticeable weaker...as expectable...??? What the heck is going on here? Despite TGSL works really good and calm....i am confused. I do not understand how speaker resistance can provoke false signal here??? Is it some kind of intermodulation here?
Looking back to partially correct Relic Hawk schematic i remember very well simillar audio and small transformer with some extra components there?
Did they have same problems in Minelab and solved it with that transformer?

I would not start this thing again but i need complete understanding of this.Also audio is weak now....Again (you'll laugh on me) if i put 1M resistor parallel to diode, even if i have 18 ohms now at output, 1M resistor causes same falses as from begining? Sort of "echo"; beep,beep,beep....once coin is moved over coil....
I 'll repeat; TGSL is working fine as i described....BUT I HAVE STRONG FEELING THAT PROBLEM IS NOT SOLVED COMPLETELY YET!??!!
Can you beleive this?
Nightmare!

[ivconic]

And here is what i gainedd with good capactior...But i had to put 330pF to streighten up signal. When 100pf is on the place oscilogramm is still "broken" ...