TESORO GOLDEN SABRE

[simonbaker]

Pictures are much better. Will take a little while to study.

TX signal missing on some. Was it there when you took picture but camera shutter missed sweep?

You can compare phase differences of your good circuit with the troubled one using same traces as in pictures. They should be about the same. If not, then we look further.

I assume coil works much better on the other circuit?

Regards,

-SB

[Ultimate_Haze]

Sorry that it took me so long.Hope this pictures are better.
Yes I have other device that is almost OK.
You want me to scope same points?

[simonbaker]

Ultimate_Haze: What kind of digital camera do you have? It may be better to take a little further away for better focus -- and/or use tripod for steadier pictures, to make sharper. And/or use "close-up / macro" setting if you have one.

Regards,

-SB

[simonbaker]

Ultimate_Haze:

It does take persistence to find subtle problems. If anyone thinks this is thread clutter, we can start a new thread for troubleshooting individual's MD problems.

I suggested new pictures of U101 pin 7 because that would be affected by wrong capacitors you discovered.

However, if oscilloscope was set wrong (trigger or vertical mode), you can take new pictures of other outputs also. As we discussed, I recommend trigger on TX channel, and use ALT mode.

Here are some more oscilloscope traces that would be useful -- each compared to the TX signal as before (dual trace):

1a. gate of JFet TR4 (disc detector) ,disc mode, with disc pot to left.

1b. gate of JFet TR4 (disc detector), disc mode, with disc pot to right.

1c. gate of JFet TR4 (disc detector), all metal mode, GB pot to left.(if signal disappears, back off a little)

1d. gate of JFet TR4 (disc detector), all metal mode, GB pot to right.(if signal disappears, back off a little)

2a. gate of JFet TR5 (GB detector) with GB pot to left. (if signal disappears, back off a little)

2b. gate of JFet TR5 (GB detector) with GB pot to right. (if signal disappears, back off a little)

Regards,

-SB

P.S. If you have more than one TGSL circuit, it is very helpful for troubleshooting to compare them.

[simonbaker]

I have check all several times.Couldn't find mistake.Measure all that I could.
And everything seams to be ok.
So this morning I have found that when bought 10p and 15p caps the seller have give me 10n and 15n.Damn stupid guy.
Now after replacing I have both chanels working.And sens increce.Still too low.But this is maybe up to coil.
Now I will clean PCB again and will try to make new coil.
I wonder could this mismatch made some harm to other components?


p.s. porkluvr the schematic and PCB are working OK.I were searching for mistake the I have made!Anyway thanks for attention.

That is good you found capacitor errors. Would you make new picture of TX signal vs output of U101a pin 7 (RX preamp) with corrected capacitor? The other outputs probably not affected, although all-metal JFet gate signal would be fixed too.

Can you tell us the model of your oscilloscope and maybe a link to specs or manual? Just to make sure you are triggering on TX only? I think you probably are, but need to make sure.

The disc signal with all the oscillations looks bad but even Molzar's original TGS had some of that, so I don't know how important it is to clean up -- I do it anyway in my circuits using a different circuit than porkluvr. But I think many people have good TGSL even with such oscillations!

I agree at this point the coil is probably the important factor. Those pesky coils....!

-SB

[Ultimate_Haze]

I have check all several times.Couldn't find mistake.Measure all that I could.
And everything seams to be ok.
So this morning I have found that when bought 10p and 15p caps the seller have give me 10n and 15n.Damn stupid guy.
Now after replacing I have both chanels working.And sens increce.Still too low.But this is maybe up to coil.
Now I will clean PCB again and will try to make new coil.
I wonder could this mismatch made some harm to other components?


p.s. porkluvr the schematic and PCB are working OK.I were searching for mistake the I have made!Anyway thanks for attention.

[Ultimate_Haze]

TX -5V/div in all pic.s
1.TX_VS_U101 pin1/5V
2.U101 pin1 only
3.TX_VS_U101 pin7/0.1V
4.U101 pin7 only
5.TX_VS_U102 pin1/2V
6.U102 pin1 only
7.TX_VS_U103 pin7/2V
8.U102 pin7 only

[porkluvr]

If that jittery waveform is from the LF353 pin-7, you should probably use a lower value of feedback resistance in the DISC circuit. Remember that the original TGS had a 10k notch pot in parallel with DISC. (That is, 10k according to the only schematic I have available, right or wrong.) Higher feedback resistance increases the chance of amplifier instability, and makes it more noticeable when it does occur. Removing the parallel notch pot without adding a "filler" increases that resistance from the original design value.

Another possibility is to add a small value capacitor in parallel with the feedback. It will have some affect on the overall phase relationship setup, but you might not notice and be able to ignore it. Look at the Bandito schematic to see what I mean.

If you have instability that just won't go away, try using lower feedback resistance AND adding about 5~10pF.

Changing the DISC pot to 10k (or adding a 10k parallel resistor (will have neglegable effect on the range of the DISC pot, however the slope of the control may be different, judging from my virtual testing.

[simonbaker]

Ultimate_Haze:

Thanks for pics.

1. Are you triggering on TX only, or both signals of dual trace? It is important to trigger on TX only so we can see phase relationship.

2. Would you please provide descriptions for each picture, what each trace is and what volts/div for each trace is?

There should be four pictures, outputs of U101a, U101b, U102a, U102b. Each one should also have TX signal as one trace.


The trace with all the jaggies looks like output of U101b. But the phase does not make sense to me, unless you are triggering on both input signals.

Is it possible you connected the TX signal to the + (non-inverting) input of U101b (disc op amp) instead of the - (inverting) input by mistake? That might also explain it.

-SB

[Ultimate_Haze]

Hi,
Simonbaker.
So I try with another coil/DD22-TX=5,84mH;RX=6,2mH/.
Voltages are U103 pin3 -0,06;pin5 0,00.
All measurments were taken in 20Vrange DC volts.Disc mode
Turning disc pot change U103pin3 value.It starts from -0,06 and in the end shows -0,00.Turning GB trimer change U103 pin5 value also.Starts from 0,00 and at the end show -0,04.
But still detects 2cm nikel coin from only few cms.And no ALLM mode.No sound at all.Not even beep.
Have a technical problem with the pic-s.Will hand draw the diagrams and post them tommorow.

[xix]

TGSL frequency

I saw it somewhere at the forum, but I can't find it any longer...
What is the formula for calculating the oscilation frequency of the TGS?
Cheers

[simonbaker]

Hi,
Simonbaker.
Its same with 3 diferant coil.
Thats why I think its further in the chain.
I am prepering pictures now.But which outputs A or B?

All of them are important for this. One picture for each output, showing TX signal and one of the outputs on dual trace. Let us know volts/div for each trace.

It might be further in chain, but still should check these front end outputs first.

U103
pin1,2,3 0,00;pin4 -6,47;pin5,6,7;pin8 8,14

Would you check again voltages on pins 3 and 5 of U103? (the + input pins). They are not usually exactly 0 volts, although it is possible to null the coil to make that, or to turn the disc pot or the GB pot to get to zero.

Check that turning disc pot changes the voltage at pin 3, and turning GB pot changes voltage at pin 5. This assumes you have some kind of null signal at U101 pin 7, which I think you must if you get any detection at all, even though you measure zero (DC volts?).

Regards,

-SB

[Ultimate_Haze]

Hi,
Simonbaker.
Its same with 3 diferant coil.
Thats why I think its further in the chain.
I am prepering pictures now.But which outputs A or B?

[simonbaker]

Thanks but nope.Cable is ok.Coil is not perfect but fine.
There should be something mistaken.
IC voltages are:
U101
pin1 0,27;pin2 0,24;pin3 0,00;pin4 -6,47;pin5 0,00;pin6 0,00;pin7 0,00;pin8 8,14
U102
pin1 -3,44;pin2 0,09;pin3 0,00;pin4 -6,47;pin5 0,00;pin6 0,00;pin7 -3,33;pin8 8,14
U103
pin1,2,3 0,00;pin4 -6,47;pin5,6,7;pin8 8,14
U105
pin1 7,48;pin2,3 0,00;pin4 -6,47;pin5,6 0,00;pin7 8,14;pin8 0,14
U106
pin1 -6,47;pin2,3 0,00;pin4 -6,47;pin5,6 0,00;pin7 -6,47;pin8 8,14
U104
pin1 -6,33;pin2,3 0,00;pin4 -6,47;pin5 -6,33;pin6 0,00;pin7 8,14;pin8 0,27

Voltages are 8,14 and -6,36 at begining.And I can see small change in - in RX stage -6,47
This is with one already sealed coil.There should be some mistake because no ALLM mode at all.

Dual scope traces needed, show TX oscillator signal compared to outputs of U101 and U102 to start with.

Also try other coil, see if same.

Regards,
-SB

[Ultimate_Haze]

Thanks but nope.Cable is ok.Coil is not perfect but fine.
There should be something mistaken.
IC voltages are:
U101
pin1 0,27;pin2 0,24;pin3 0,00;pin4 -6,47;pin5 0,00;pin6 0,00;pin7 0,00;pin8 8,14
U102
pin1 -3,44;pin2 0,09;pin3 0,00;pin4 -6,47;pin5 0,00;pin6 0,00;pin7 -3,33;pin8 8,14
U103
pin1,2,3 0,00;pin4 -6,47;pin5,6,7;pin8 8,14
U105
pin1 7,48;pin2,3 0,00;pin4 -6,47;pin5,6 0,00;pin7 8,14;pin8 0,14
U106
pin1 -6,47;pin2,3 0,00;pin4 -6,47;pin5,6 0,00;pin7 -6,47;pin8 8,14
U104
pin1 -6,33;pin2,3 0,00;pin4 -6,47;pin5 -6,33;pin6 0,00;pin7 8,14;pin8 0,27

Voltages are 8,14 and -6,36 at begining.And I can see small change in - in RX stage -6,47
This is with one already sealed coil.There should be some mistake because no ALLM mode at all.