TESORO GOLDEN SABRE

[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.

[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]

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

[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.

[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.

[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.

[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.