TESORO GOLDEN SABRE

[cristiano.sar]

I have a new doubt. When setting the GB trimmer, I've read that the sensitivity pot should be at minimum. I am able to reject the ferrite with this setting (GB trimmer at middle and sens at minimum). Although, when I move sensitivity to max, the ferrite is detected. Is this normal? Thanks.

[cristiano.sar]

Has anyone a picture of a built TGSL-EDU board so I can compare the components with mine? After a long time without touching the project, I decided to return to it and I'm still with the same issue reported in previous posts: I can only use the sensitivity pot at minimum, it i turn it higher a constant tone is heard (https://youtube.com/shorts/tP9NpLMGQfM). Coil is not shielded for now as i'm only testing it statically. Thanks.

I've just found the problem, something with the LM308s, I changed them to supposed original versions and it worked ok now.

[cristiano.sar]

Thanks.

The coils are not shielded yet. I want to shield them inside the casing, with graphite.
The 15nF RX capacitor is connected to the coil wires so I could change it easily, that why you dont see it in the photo.
I will try other speaker (I'm using a piezo buzzer) and shield the enclosure.

Thanks.

[kt315]

Coils are not shielded?

if a coil is not moving (in space), rests on a table, static, then the shielding is unnecessary. just you take the coil and move it up down - you have to shield the coil.

[ivconic]

I can't see RX capacitor 15nF on the pcb?
Without it it will work similar as on your video.
Coils are not shielded?
Behavior on video is typical when the last comparator goes into self oscillation.
To mitigate this to some extent; use 32-64 ohm speaker.
But first things goes first; shield the coils, shorten the wires that comming from pcb and put the pcb into shielded enclosure.
If not the whole enclosure, at least make sure the pots and switches are all tied to metal front panel and grounded.
Keep in mind; those old Tesoros are all coming into metal enclosures well grounded.
And all use 32-64 ohm speakers.

[Toros]

Another doubt, I'm my EDU board, there are some small holes that are not connected, should I connect them with bridge wires? Thanks

These are through holes from one side of the board to the other. Don't touch them.

[cristiano.sar]

Another doubt, I'm my EDU board, there are some small holes that are not connected, should I connect them with bridge wires? Thanks

[cristiano.sar]

After changing the TL071s to LM308s, now I have much better sensitivity, but it is only usable when the sens pot is at almost minimum. If I increase it, the detector becomes very unstable, a continuous beep can be heard, you can see it in the video:

https://www.youtube.com/shorts/ENlC_If9tP8

[cristiano.sar]

In Brazil, the best source of original ci's is electronic scrap.

Thanks, some time ago I bougth an old TV but can't find any usable components for the MDs I'm building, but I will keep an eye in other used electronic devices.

[Emersonpaz]

In Brazil, the best source of original ci's is electronic scrap.
I buy the TL series from this seller on aliexpress, all original from Texas Instruments.

Aoweziic Raw material spot Store
https://a.aliexpress.com/_m0Xo1Gj

[cristiano.sar]

Hello Cristiano, at a quick glance I can see that your TL071s are fake.TL071 original from Texas does not have this half moon.

Thanks, Emerson

I'm waiting for LM308s now, lets see if they are real, anyway, imported some more LM308s from other countries to see what we can get.
Anyway, what is your best source for good quality components here in Brazil?

Thanks.

[Emersonpaz]

Nice, My coils are 6.0mH and 6.5mH more or less and I made the elliptical format (copied from a tesoro widescan 9x

Coil:

EDU board:

I noticed that I added the TL071 with the 100pf cap, I'm waiting for LM308 that will arrive today to see is something changes in performance (I dont know if these ICs has something to do with it).

Hello Cristiano, at a quick glance I can see that your TL071s are fake.TL071 original from Texas intruments does not have this half moon. Follow the image of the original below:

perhaps the same reason why your performance is lower

[MOR_AL]

Hello Cristiano.

I have had several problems with operational amplifiers (OA) purchased both locally and via Chinese websites. I even returned a batch of OA purchased in China. The seller had assured me that the OA were new. I replied, "They may be new, but they are fake."

I ended up designing, assembling and testing a circuit that identifies whether the OA is fake.

I made a video, which is in Brazilian Portuguese.

If you are investing a good amount of money in your project, it might be interesting to watch the video.

First video

https://youtu.be/1rorBNa5q1g

Second video

https://youtu.be/vzWiiXP-htE

Best regards
Moris

[ivconic]

I forgot the precise specs, but I think that 071 is not good substitution for LM308.

[cristiano.sar]

Nice, My coils are 6.0mH and 6.5mH more or less and I made the elliptical format (copied from a tesoro widescan 9x

Coil:

EDU board:

I noticed that I added the TL071 with the 100pf cap, I'm waiting for LM308 that will arrive today to see is something changes in performance (I dont know if these ICs has something to do with it).