TESORO GOLDEN SABRE

[dbanner]

Welcome back,
Thanks for the clarification, you're really good at this, really. I'm just learning and I can't judge my oscillogram like that, but I guess it's not bad. Besides, it is not a real oscilloscope, but a computer adapter. I can't expect her to work better.
But let me tell you something: with my PCB, I visited a friend who has an old Russian oscilloscope, still analog (I can't find what model it was on the network) and not fully functional (no electrodes and problems with switches). And when I connected the PCB to it, for the TX waveform it showed exactly the same sine wave distortion as in the Don Bowers documentation.
What do you think - can I already think about GB and discrimination at this stage?
Greetings.

Yes.

What about the audio? Does it respond to metal object.

Also notice as you move Rx coil, the signal amplitude dips to minimum and then rises again as you emerge on the other side of the null point.
So you want to be 20 degrees, but how do you know which side?
20 degrees leading or lagging? This is where you look at pictures of dbowers.

Also as I noted previously, so long as you can reject ferrite within the range of the gb trimmer and get good distance and discrimination, you can be assured that it's going to be pretty close to the 20 degrees required for this circuit. If you have 19 or 21 doesn't matter.

[Majster]

Welcome back,
The sound is present from the beginning of the construction. Reacts to any metal in All mode. I tried to test the discrimination when the coils were not yet well corrected with capacitors. It worked so that it was rejecting ferrite by then, and sometimes I thought it was rejecting other metals as well, or all of them. You know how it is: when you are not sure about the reaction, you imagine it, and the more you want to see it, the more you imagine it. But in such cases, I prefer to remain skeptical and not rely on my imagination.
Looking at my waveform, the RX seems to be ahead of the TX, but I don't know if it's good or bad. Should it be ahead or delay? How is this done? How to cary about it?
I plan to attempt GB tuning and discrimination this afternoon. I just preferred to make sure it made sense beforehand, because my previous attempts did not satisfy me.
Yesterday I chose elements so that their values were relatively constant and equal, by the way I calibrated the second capacitance meter, now I have 2.
And what about these elements? Can any more be changed?
Greetings.

[Majster]

Welcome back,
I have just tried to check how GB and discrimination work. And unfortunately there are problems again. At the beginning I switched to All mode. I set all the potentiometers to the middle of the scale. I found a position for the coils that gives the minimum AC voltage between ground and IC101 / 7. Today I was able to get 0.4V AC. Then I started turning the GB potentiometer until it rejects ferrite. The documentation says so. The position of the potentiometer at which the ferrite is rejected is basically at the beginning of the scale (left). When I turn the knob clockwise, the ferrite is still visible. Other metals too (copper, aluminum, steel) are visible. So I left the GB potentiometer at the beginning of the scale on the left. Detection may not be the best (15-20cm), but acceptable at this stage of construction. I switched to Diss mode. Detection has ended. Regardless of the position of the Diss and GB potentiometer and the sensitivity on the PCB, there is no detection. Everything is rejected, every metal. When I go back to All mode, every metal gives a signal again. When I go back to Diss mode, all metal disappears. There is no combination of potentiometers where some metal gives a signal. I'm worried. What could have happened? What should I check now?
Greetings.

[dbanner]

Check all metal/discrimination switch is wired correctly.
Check for waveform at gate of tr4 when switch is set for discrimination.

On a different note, many of opamp chip on the market are fake, especially from eBay.
Make sure you have genuine opamps.

[Majster]

Check all metal/discrimination switch is wired correctly.
Check for waveform at gate of tr4 when switch is set for discrimination.

On a different note, many of opamp chip on the market are fake, especially from eBay.
Make sure you have genuine opamps.

Welcome back,
I checked all metal/discrimination switch: they are wired correctly.
I did this: I finished the second PCB (PCB2). I applied changes to it:
both 2N2907 → BC557
both 2N2222 → BC547
both LM308 → TL071
I chose all capacitors and resistors so that they were as close to the measurement value as possible to the declared value. So that they should be equal to the description in the diagram, not just close. The differences from the declared one do not exceed 1%.
I got the values of the supply voltages + 8.0V and -5.5V. On PCB1 it was +8.0 and -7.0V.
I tuned both coils to this board according to your directions, which is exactly as before, but I left 14.2kHz on TX (i.e. C1 = 220nF, C2 = 22nF, no correction capacitance) and I adjusted RX to 15.8kHz for a shift of 1.6 kHz (it required 220pF soldering parallel to C6, so now C6 '= 15nF + 0.22nF = 15.22nF).
I connected both coils and tried to get the minimum AC voltage between IC101 / 7 and ground. About 0.38V AC was obtained. It is not possible to receive 5mV AC. I assume that with this minimum value, the voltage at the RX connectors is also minimal, I did not check it. I checked how detection works in the All mode. It works, maybe not great, rather weak, but it works.
I switched to discrimination mode. PCB2 behaves almost exactly like PCB1. There is no possibility of obtaining discrimination.
I went back to PCB1.
I tried to set the required AC values (as described above). With the minimum AC voltage value between IC101 / 7 and ground (about 0.45V AC) I recorded the waveform / oscillogram on the TR4 gate. File in attachment.
I know that many of the elements on the market are non-original, but I cannot tell them apart. I try to buy from reliable suppliers, but it doesn't always work. You can check the transistors by yourself, but I can't check the integrated circuits myself.
Greetings.

[dbanner]

Check the legs of jfets for correct pinout.
Which jfets are you using for tr4 and tr5?

Oscillogram for gate of tr4 does not look right.

You could remove centre wire from switch and take oscillogram of output of pin 1 of comparator 102a.
Check your comparator circuits.
You must have proper switching waveforms for the jfets.

[dbanner]

You might be suspicious that your comparator lm393 chip is not comparator chip but is really a normal op amp masquerading.

[dbanner]

Perhaps you can test.
Looking at internal schematic for lm393.
If you put multimeter on diode check, you should see voltage drop of base/ collector junction between either input pin and pin 4 of comparator chip lm393.( Remove chip from socket)
A regular op amp will not show up like this.

[dbanner]

On separate note, I discovered easy way to distinguish real NE5534 chip from fake.
Their are anti parallel diodes across the inputs.
Unique to this chip.
A multi meter on diode check range will confirm this if you have the genuine chip.
If not, you are sure to put in trash bin.

[waltr]

Yes, tr4 scope picture is not right. This is why it does not discriminate.
Refer to the TGSL 101.pdf for what the Gate of TR4 should look like.

[SkyeHi]

hi cristiano, i have two of these i bought a kit of parts from ebay.............the only downside is you must use a good quality battery and keep an eye on it, the inbuilt battery volt meter tells lies, it will say 8.4v but really be 6.9v so just use a duracell or energizer and disconnect it when not in use.
low power makes the meter readings wrong.
[ATTACH]56476[/ATTACH]

ahhh ha, thanks for that sinclair.
Late to the party as usual but I also have one of these kits, just finished winding a coil and expecting 415/465uH, instead I got 8mH. I was blaming the weave geometry, the thin ply former I used instead of the acrylic one that snapped. Snow showers on a gale of wind atm, as soon as it eases I'll be out in the workshop to check that bloody battery.
Thank you all, great site this.

[Majster]

Check the legs of jfets for correct pinout.
Which jfets are you using for tr4 and tr5?

Oscillogram for gate of tr4 does not look right.

You could remove centre wire from switch and take oscillogram of output of pin 1 of comparator 102a.
Check your comparator circuits.
You must have proper switching waveforms for the jfets.

Welcome back,
I did this: I searched for all LM393 in my stocks and it turned out that there are 3 populations of different designations, maybe that's what the manufacturers mean. Of course, there is LM393 on all of them, but the extra numbers / letters / symbols are different. I chose the first pair other than the ones I had in PCB. I took out the previously used ones (both) from the PCB and put this pair in positions IC102 and IC106. I turned the chip on and tried to set the coils to the minimum AC voltage between IC101 / 7 and ground. It turned out much worse than before, just slightly below 1V AC. I turned on the diss mode. Nothing has changed, discrimination still does not work. I didn't even record an oscillogram on the T4 gate. I found another other pair of LM393. I put in both instead of the previous ones. I repeated the setting of the coils as above. It turned out worse again. I put Diss Mode on and a long continuous beep came from the speaker. I'm back in All mode. Silence, regardless of the presence of metal / ferrite above the coils. I checked IC102 - very hot, I assume it got burnt but why? The previous ones did not heat up. For sure I inserted them correctly and I did not confuse pin 1 with 5. I did not short-circuit anything, I did not change anything on the PCB, nothing accidental is on the PCB or underneath. I took out the IC102, now I have an empty slot. I don't know what to check.
For the T4 and T5 positions I use the BF245c. I checked the legs, in my opinion they are correct, the gate is on the side, not in the middle. Behind the gate is the source, the last drain.
You proposed some way to test the LM393, but I don't understand your tips, I don't even know how I could connect the multimeter electrodes to this LM393. Even if I can check, and even if all my LM393s are fake, I still won't be able to buy the real ones.
This is an optimistic scenario. Because if I buy another LM393 and luckily find a real one, it may be discriminatory. But I don't know how to buy such a real LM393.
The pessimistic thing is, however, that some pair of my LM393 are correct, and the cause of my failure lies elsewhere, and I cannot locate it.
Greetings.

[Majster]

Yes, tr4 scope picture is not right. This is why it does not discriminate.
Refer to the TGSL 101.pdf for what the Gate of TR4 should look like.

I just realized that something else could burn on the PCB besides this unfortunate LM393. If so, then I won't find what it might be at all. I'm worried about the progress of my work, but I can't do enough. I don't think I will finish this project, it is too difficult for me. It's a pity because I made 2 PCBs and I think I have properly wound and tuned coils, it's a shame about it all.
Is there any simpler detector with discrimination? Obviously not BFO, something with better sensitivity. Could you recommend something with good installation and commissioning documentation? I would be very grateful. I am grateful anyway, because you help me a lot, but I must be for a weak student.
Greetings.

[waltr]

Sorry to hear all the trouble with this circuit.
The TGSL is about the simplest one with discrimination.
It is the TGS without the notch circuits.

The IDX is about the same complexity wise.

[dbanner]

I just realized that something else could burn on the PCB besides this unfortunate LM393. If so, then I won't find what it might be at all. I'm worried about the progress of my work, but I can't do enough. I don't think I will finish this project, it is too difficult for me. It's a pity because I made 2 PCBs and I think I have properly wound and tuned coils, it's a shame about it all.
Is there any simpler detector with discrimination? Obviously not BFO, something with better sensitivity. Could you recommend something with good installation and commissioning documentation? I would be very grateful. I am grateful anyway, because you help me a lot, but I must be for a weak student.
Greetings.

I think your problem is very simple. There is some error in the circuit of the lm393.
I suggest re-evaluating the PCB layout and components around this area. Check every component.
LM 393 getting hot is very bad sign. Now you describe continuous beep and overheating.