Surf PI Pro

[Jose]

delay on max (turned to right)

If you have the original delay, that consists of R25 to 5.1K and 10K pot delay. You can replace the 10K, by 50K pot, and slowly increase clockwise to achieve the best sensitivity.

[sdesic]

Jose,

Thank you for your help!
I will make another coil with more turns when I receive LRC meter from China.
For now it is good, I must dig a little (not too much deep).
I will try this surf pi pro in field out of power and other disturbance.
Sinisa

[sdesic]

Best results are with gain on 50%
tresh on max (turned to right)
delay on max (turned to right)

[Jose]

Sdesic
You are between 22 and 25 cm for one euro, and not bad, I think it can be improved, the coil of 21 turns, I get a value of 230 uH, according MiscEL.
Increase the turns in the coil should improve performance. It should also increase the delay, since the original values give 10 to 15 us, for coil fast.
Our homemade rolls, are slower.
To give you an idea, in my SurPI, minimum delay resistance is 25K, (R25) and the delay is 50K pot, with values below works,works just but increases noise.
Jose

[sdesic]

R10 is set - pin 6 has 0,07V

[Jose]

Do the opposite.
Try to gain control ("gain") at maximum.
Then reduce the threshold to the point where it gets maximum sensitivity.
R10, set to a voltage between 0 and 500 millivolts, (0 to 0.5 volts), measured between GND and pin No. 6 of 5534. With the coil away from all metal.

[sdesic]

changed that R18 from 47k to 22k
now with tresh at max at sens at half I get silence
and detect 1 euro at 22 cm

[Jose]

Sdesic
Pardon the error, is not R28. "Is R18".
The tone threshold should move from silence to audible more or less in the center of the potentiometer, control threshold.
This should occur while the delay controls and max gain.
I leave for a while, then I'm still here.
Jose

[sdesic]

what can be done with offset r10 trimmer ?

[sdesic]

if treshold is at max and gain at max it should be no sound or constant ?
with delay at max

[Jose]

with max treshold it has some audio - little short beeps

I would have to hear a continuous tone.
Test replaced R28, by 22K.

[sdesic]

Threshold to maximum audio tone is heard?.
Silent?

with max treshold it has some audio - little short beeps

[sdesic]

R2 at 4k I can get 25 cm but it not clear ... making noise with no metal around
must try somewhere without RF inteference
Coil is 40 cm off ground - reinforced concrete
delay pot is at max 9.5k

I will adjust R2 to 3k6 to reduce heating and consumtion for now
it gives 24-25 cm at max gain - with some noise

[Jose]

Threshold to maximum audio tone is heard?.
Silent?

[sdesic]

R2 is now set to 3.6k and I have 22 cm
gain is now 3/4 and treshold is on max