TESORO GOLDEN SABRE

[Max]

Max can you scope your LF353 pin 1. and post it here?

Something is "misty" here???

Hi,
yes, of course, but I need a few time (maybe I can for this evening or tomorrow in worse case).

Best regards,
Max

[ivconic]

No problem of course!
I'll be awake until 4 o'clock this evening (morning)....sa any other night...
If you achive to do that today, fine. If not, than tomorrow is just fine also..
Thanks in advance!
Regards!

P.S.
Now you have rough picture of my oscillogramms....You can do some rough comparsions, also, with results you gain measuring your device...If you notice major differences, let me know..
Also you can suggest me what other spots i can measure and get oscillogramms for further comparsions....Actually you can suggest me now, so i'll prepare those for tonight..

[Max]

No problem of course!
I'll be awake until 4 o'clock this evening (morning)....sa any other night...
If you achive to do that today, fine. If not, than tomorrow is just fine also..
Thanks in advance!
Regards!

P.S.
Now you have rough picture of my oscillogramms....You can do some rough comparsions, also, with results you gain measuring your device...If you notice major differences, let me know..
Also you can suggest me what other spots i can measure and get oscillogramms for further comparsions....Actually you can suggest me now, so i'll prepare those for tonight..

Hi,
sorry for bad quality ... I need a tripod or something to do better cause of latency required inside by camera to shoot pictures.

Actually I haven't around so used hands... and pictures are about "moved"...anyway you could see my signal is different:

-on top you see the signal at osc, collector of 2n2907
-under is the pin1 of lf353 and it's parabolic like... with some spurious sinusoidal noise

Channels amplitude is 5V/square (but can you see squares ?)

This time I can't do better...

Hope you see the difference!

Kind regards,
Max

[Qiaozhi]

So i listened Quiaozhi's suggestions...i played arround KOP's hysterezis....not even close! Same behavior...!

I decided to take shots from some oscilograms....Yes i know; my osci. is obsolete and funny...yet here are some shots...
Only thing is not clear to me is osci at 1.pin of LF353?????

OK - the top two traces are the inputs to the synchronous demodulators. These look ok to me. In trace one you can see that GEB is sampling at the positive-going zero-crossing point. In trace two you can see the DISC sampling should be at the peak of the waveform for ferrous discrimination, so I guess the DISC pot is turned fully anti-clockwise here.
The waveform at the LF353 pin1 looks wrong. It's being driven into saturation and there's some instability there. I've used this configuration in the past, and it's clearly not right. Have you looked at what happens to the waveform when you turn the DISC pot? There's definitely a problem here. Are you sure you measured the correct point in the circuit? I have to ask ...
Receive and transmit look good.

Can you also probe the outputs of U106A and U106B? In particular, look at the waveform when you wave a coin at some distance from the coil so that the audio signal is weak.

[Max]

OK - the top two traces are the inputs to the synchronous demodulators. These look ok to me. In trace one you can see that GEB is sampling at the positive-going zero-crossing point. In trace two you can see the DISC sampling should be at the peak of the waveform for ferrous discrimination, so I guess the DISC pot is turned fully anti-clockwise here.
The waveform at the LF353 pin1 looks wrong. It's being driven into saturation and there's some instability there. I've used this configuration in the past, and it's clearly not right. Have you looked at what happens to the waveform when you turn the DISC pot? There's definitely a problem here. Are you sure you measured the correct point in the circuit? I have to ask ...
Receive and transmit look good.

Can you also probe the outputs of U106A and U106B? In particular, look at the waveform when you wave a coin at some distance from the coil so that the audio signal is weak.

Hi,
yes his lF353 goes into saturation at top of curve... and that's no good... but I think there is a problem on the sampling at DISC (fet #2).

Seems a double pulse of sampling.

Kind regards,
Max

[ApBerg]

Lf353-1

The signal at 353-1 is wrong......!?, think you both use wirewound disc pot?
Think it must be a nice sinus !
Wil make some pictures, mail them.

Ap

[Qiaozhi]

Hi,
yes his lF353 goes into saturation at top of curve... and that's no good... but I think there is a problem on the sampling at DISC (fet #2).

Seems a double pulse of sampling.

Kind regards,
Max

Yes - there is a problem with the sampling in the DISC channel (fet #2), but at least it's sampling in the correct place. I think the double pulse is happening because the sample pulse has that strange instability.

The signal at 353-1 is wrong......!?, think you both use wirewound disc pot?
Think it must be a nice sinus !
Wil make some pictures, mail them.

Why do you think a wirewound DISC pot would cause any problems?

[ApBerg]

LF353-1

Hello Frends.

Qiaozhi, in the past I had some problems with wire wound pots, when replaced by a 'normal' pot the problems were gone, can it be that there is an L function ?

Well made some screenshots, transmit sinus is 2 v p/p also the 353-1 is 2 v p/p for the r25 and r26 signals it is 0.2 v p/p ( I hope..... can be wrong )

First is LF353-1 then two from r25-q7 then two r26 q6

Ap

[ivconic]

OK - the top two traces are the inputs to the synchronous demodulators. These look ok to me. In trace one you can see that GEB is sampling at the positive-going zero-crossing point. In trace two you can see the DISC sampling should be at the peak of the waveform for ferrous discrimination, so I guess the DISC pot is turned fully anti-clockwise here.

The waveform at the LF353 pin1 looks wrong. It's being driven into saturation and there's some instability there. I've used this configuration in the past, and it's clearly not right. Have you looked at what happens to the waveform when you turn the DISC pot? There's definitely a problem here. Are you sure you measured the correct point in the circuit? I have to ask ...
Receive and transmit look good.

Can you also probe the outputs of U106A and U106B? In particular, look at the waveform when you wave a coin at some distance from the coil so that the audio signal is weak.

Actually it is not fully anti-clcokwise...Damn! It is a bit over half in clockwise direstion!???
Yes i suspected signal from pin 1. of LF 535 at once...!I?
I'll scope outputs of U106A and -II- b and see what happens...

I was absent a while.... Now have to go again. Be back soon...

[ivconic]

Yes - there is a problem with the sampling in the DISC channel (fet #2), but at least it's sampling in the correct place. I think the double pulse is happening because the sample pulse has that strange instability.


Why do you think a wirewound DISC pot would cause any problems?

Damn! You are right! And i suspected scope!? It is obsolete and very old so sometimes it is doubling ..gramms when turn one switch on it. But this time i am sure it is not a case, cose i cleaned that switch to avoid internal scope hums...Damn!

[Qiaozhi]

Hello Frends.

Qiaozhi, in the past I had some problems with wire wound pots, when replaced by a 'normal' pot the problems were gone, can it be that there is an L function ?

Well made some screenshots, transmit sinus is 2 v p/p also the 353-1 is 2 v p/p for the r25 and r26 signals it is 0.2 v p/p ( I hope..... can be wrong )

First is LF353-1 then two from r25-q7 then two r26 q6

Ap

Yes - these all look as expected to me.

Ivconic - study these waveforms. This is what they should look like.

[ivconic]

ApBerg do you have ocassional beeps as i described? Or it is working stabile?
Is it Goldy pcb or larger one?
Regards!



Come to think again; large pcb is working just fine, i put LM308 in plastic case on it.
Goldy pcb is not working fine, i put LM308H on it...?! On all 8 pcb's...
But this wrong oscilogramme is measured at LF353..not at late stages...?!

About metalic case of LM308H; is it connected somewhere in internal wirements? Have to look datasheet....
If not than i'll connect those to gnd...if yes than...!?
Front end with LF353 is so simple...i dont understand.I put very same components at all 8 pcb's, same as on large pcb..?

[porkluvr]

OOh, ooh!

Ivconic, the reason that the pin 1 waveform is so out of control, is because you have removed the original GS notch level 10k potentiometer
that was directly paralled with the 100k discriminate pot. By removing the notch circuit, you have increased the gain of the opamp - at
the same time as you also increase the likleyhood of oscillation because of the higher feedback resistance.

Either change to a 10k Disc pot, or parallel a 10k fixed resistor across the 100k pot, and see what happens. It will very likely cause a different curve
to the Discrimination potentiometer effect (to be more like the original), but things should smooth out.

The LF353 is not a rail-to rail opamp. By having raised the circuit's gain, you have run out of dynamic headroom!
It feel stupid for not realizing this sooner.

[ivconic]

If that will turn as main source of problems....than i'll feel stupid even much more!!! What to say? Either you right or wrong, thank you very much for effort. I will obey your suggestion and report here in hour or two...Right now i have some guests...wait they to go

[Qiaozhi]

Ivconic, the reason that the pin 1 waveform is so out of control, is because you have removed the original GS notch level 10k potentiometer
that was directly paralled with the 100k discriminate pot. By removing the notch circuit, you have increased the gain of the opamp - at
the same time as you also increase the likleyhood of oscillation because of the higher feedback resistance.

Either change to a 10k Disc pot, or parallel a 10k fixed resistor across the 100k pot, and see what happens. It will very likely cause a different curve
to the Discrimination potentiometer effect (to be more like the original), but things should smooth out.

The LF353 is not a rail-to rail opamp. By having raised the circuit's gain, you have run out of dynamic headroom!
It feel stupid for not realizing this sooner.

Hi PorkLuvr!
Well spotted. That's just what this forum is all about.

Ivconic - now go and buy a decent scope.