[nebulos]

Hi everybody,

I was hesitating to create a new post, but I will try first with this 6 months old one!

I'm experimenting a Surf PI 1.2 on a breadbord, and I don't succeed to identify my problem: I have a sound, but it decreases when I approach an objet to the coil. So I think that U4 or U7 (or both?) is not working, because the modification of the delay (P3) doesn't seems to have any impact on the final signal. Also for the sound I still have the pulse emitted to the coil (if I understood well the circuit U4 and U7 reject the pulse transmitted to the coil to just have its response).

I already tried to change U4 and U7, without any result. Do someone have an idea about what point I should check? (Even if I don't reject the possibility of a mistake about that, I already checked at least twice all my connections, resistors values and orientation of transistors). I have a noisy 20MHz oscilloscop to help me, is someone can describe what kind of signal I should expect at some points of the circuit.

Anthony.

[Paul van Heerden]

Hi everybody,

I was hesitating to create a new post, but I will try first with this 6 months old one!

I'm experimenting a Surf PI 1.2 on a breadbord, and I don't succeed to identify my problem: I have a sound, but it decreases when I approach an objet to the coil. So I think that U4 or U7 (or both?) is not working, because the modification of the delay (P3) doesn't seems to have any impact on the final signal. Also for the sound I still have the pulse emitted to the coil (if I understood well the circuit U4 and U7 reject the pulse transmitted to the coil to just have its response).

I already tried to change U4 and U7, without any result. Do someone have an idea about what point I should check? (Even if I don't reject the possibility of a mistake about that, I already checked at least twice all my connections, resistors values and orientation of transistors). I have a noisy 20MHz oscilloscop to help me, is someone can describe what kind of signal I should expect at some points of the circuit.

Anthony.

Welcome to the forum

I unfortunately am not the best with electronics. I think i was fortunate to not have many problems, and also to have a few members like Louis Kriedemann to help me out. Louis and another member Barney might be able to help you out with the problem you are having.

I hope you come right. You can also post your problem on the Geotech forum. They have some very knowledgeable guys there too

http://www.geotech1.com/forums/forum.php

[nebulos]

Thanks, I will ask my questions on the Geotech forum too.

...and like many answers (or at least a part in this case) are answered with well-formulated questions, I come to realize that I made a big mistake. I wanted to ask to be sure that it was a little mistake on the scheme with the alimentation of the LM358 like the pin 4 and 8 were missing. In fact they are on the scheme, but the name is missing. On the very little part at the center top of the scheme (pins and a capacitor linked to V- and V+), I thought U4 was connected with 4, 7, 8, 14 (I know, it's obvious now), whereas it's just the 7 and 14 for U4 and 4 and 8 for U3. The U3 name is missing.

So I think my circuit is better now. But I don't have anymore sound.
The P3 have a little efffect on the amplitude of the pulse which arrive to the pin 9 of U4C.
Here I am.

[Paul van Heerden]

You say you now do not have sound. Are you sure your coil is wired up correctly?

[nebulos]

Yes the coil is ok. I have a signal at pin 6 of NE5534. I have something until before the D3. Nothing after. I already change the 1N4148, and checked the orientation. I continue to investigations in this part of the circuit...

[dheger]

Hi treasure hunters,
first thanks for accepting me in this forum. I found here a lot of valuable information... but still.. I would like to ask you for help.

I bought from Silverdog, UK Surf Pi kit 1.2. Everything is soldered now, I measured all values according to schema and all IC's seems to have correct values (according following table)
u2 pin 7 v 4.97 +
u2 pin 4 v 4.75 -
u3 pin 8 v 4.97 +
u3 pin 4 v 4.75 -
u4 pin 14 v 4.97 +
u4 pin 7 v 4.75 -
u7 pin 14 v 4.97 +
u7 pin 7 v 4.75 -

I have tried to build 3 different coils with different wires (last one according to this video: https://www.youtube.com/watch?v=LFZpy4sdZuk) but absolutely NO reaction when I move the iron object over the coil. I also measured the voltage change on pin 6 of the NE5534P but no change as well.

Strange thing is, that I hear sound from the speaker only when I set volume or treshold potentiomenter to specific position, no linear audible response from adjusting the volume.

Any help highly appreciated.

David