Surf PI 1.2

[warlockm42]

Hi all . I am building a surf pi detector for the second time.
First time was several years ago and it worked very good.
It was buld from a kit with the black long board pcb.
The one i am building now is using a green pcb i bought off ebay.
The detector works and can detect small metal objects at about 10cm distance. My problem is that when i turn it on and adjust vol and threshhold the sound comes for 1 second and goes.I dont have that continious sound just above silence i shoud hear. Moving pots dont change any thing exept vol. My coil is made out of 0.8mm copper enameled wire 22 turns 30cm diameter with a usb cable for connection all is 1.4 ohm resistance. I have tried several dump resistorsbetween 290 and 390 ohms and a 1k pot for adjustment but no luck. Any inputs on what might be the problem? Thanks in advance!!!

[Eddy71]

Did you buy an operational amplifier and a field effect transistor on Aliexpress?

[warlockm42]

Hi and thanks for your reply.
Only the pcb was bought from ebay.I bought all electronic componets from a local store.I also replaced all components allready , ic transistors and diodes,to make sure there is not a problem with those.

[kt315]

Apberg's long board has mistakes in layout. i can not tell you where just now. this thread https://www.geotech1.com/forums/show...f-PI-Pro/page2

[warlockm42]

Thanks for your reply. How do i know it is the specific board by Apberg? It looks identical with the black surf pi 1.2 only difference is it has more bridges.

[kt315]

pics from your side will tell us more what you bought.

[warlockm42]

Some pics from the board.I also need to state that i have cut the board in half to reduce space.I used wires to conect the 2 pieces. The problem was there before cutting the board.[ATTACH]56578

[warlockm42]

Some pics from my actual board volume and delay pots are working. Tune and offset are not working.[ATTA CH]56582[/ATTACH]

[Carl-NC]

Does it work other than no threshold? That is, if you wave targets does it respond?

[warlockm42]

Yes it will detect a coin at about 10cm distance

[Carl-NC]

Then the problem is in the back end. Double-check your values for C15, P5, P6, R29, R31-34. Make sure the gain pot is hooked up correctly.
With the coil disconnected measure the DC voltage on both sides of C15.

[warlockm42]

I will check and get back to you.Is there way you can send me the correct parts list so i can check the values ?There may be chance i have a wrong list.Thanks for your help

[warlockm42]

Eventualy the problem was spoted.It was a resistance problem after all. R18 and R22 was marked vice versa.Thank you all for your help especially Carl your guidance got me there!!!

[Carl-NC]

Problem wasn't where I thought it would be, but glad you found it!

[Justihnno]

I followed your instructions and made the PCB at home instead of using an industrial process. It works well, but I would like to measure its performance on the oscilloscope as you did in your YouTube video. I am new to this field and I would appreciate it if you could show me how to connect the oscilloscope probes to the right pins for getting similar results. My PCB does not have the test points that yours has, but it is otherwise identical.