tl12000 isn't stable

[Faycalb]

Hello dear friends, this is my first post on the forum I'm really excited about having joined this community I made tl12000 twice the first one its stability was acceptable but the second was nothing but crap the problem is that whenever I adjust the 20 turn variable resistor the sound rise up right away and if I put a metal ahead of the coil it detected it but it keep sounding till I adjusted the resistance again although I all IC's I used were original I tried to change them with the other ic from the first device but nothing I keep having the same results
Any help I will be grateful, thanks in advance

[GeoMax]

Hello,

Which PCB version did you use for your TL12000 project? The TL12000 does indeed have numerous design flaws. If you fixed all the design flaws, you would have a PI-Polones ( alias Sandbank PI from 1979 ) with a dedicated sample-and-hold IC ( LF398 ) instead of a pure FET switch.

[Faycalb]

I used this one, if you have another version which include no flaws please give it to me it at least show me the fault in this version

[GeoMax]

Hello,

Actually, as far as I know, there is no bug-free version of the TL12000. The entire design is a mess. Almost every part of the circuit has design flaws. It would be too much to list them all. But for some, it more or less works. I'd rather skip this project and build a MiniPulse or SurfPI detector.