messed up my Tesoro coil (concentric)

[Koala]

all was good until I tried it in the field.


Went for connecting the RX and TX to the shield in the coil head. I know some have had trouble connecting the RX in the coil with wet grass. However while testing I found the depth to be identical but without connecting the RX the last inch the sound is more like the spits of iron so less likely to dig.


Everything tested okay on the bench. I could charge up a piece of plastic and touch the coil with it and the detector does not sound.

In the field as the coil brushes the ground/grass the detector crackles.


Just want to confirm that the problem is where I connected the TX shield. I have treated the transmit and bucking coil as one and the shield is connected to one end I suspect I should have connected between the TX and bucking coil instead.

[kt315]

what tesoro model you use?

[Koala]

what tesoro model you use?

Homemade Bandido II µMAX surface mount.


Coil I am try to copy is the 5.75" concentric


Quite impressed with its ability to discriminate iron. Over soil when the coil does not touch any grass everything is fine. Only dug one piece of iron and I thought it was iron before I dug it. This is running with the discrimination at its lowest. The no motion all metal mode is great for identify targets. Found a small piece of lead right next to a iron bar because you could hear the small gap when moving slowly in all metal mode. My IDX would not have found it. Picking up tiny slivers of metal real sharp and loud. Overall happy just need to sort out a decent stable coil.

[kt315]

look attentionally again intoinside the tesoro coil. a big problem of much people with high elecronics base knowladge they do not understand for what making the shielded layer, where it is and why. under resin you can see graphite layer, on another pic a bare wire in this layer touchingtogether to this layer. DO THIS WAY.

[Koala]

Resin layer. Shield layer. Resin layer is the way I did it. Both top on bottom of coil. Also used a bare wire but soldered it to a small square of copper to increase its surface area

[kt315]

did you check by measuring (kOhm scale) from this copper to every part of graphite layer? did you make sure there is a galvanic electric link to every part of the layer from shield wire?

[Koala]

Yes to both questions. Between 100K and 150K

Just check the coil as I have cut it open to retrieve the strain relief and lugs. Re checking and the shield has dropped to 40 to 50K. Strange when I probe the shield the numbers take a while to settle down much like a capacitor ?????

[kt315]

that is strange for me you use a cooper plate for 'to increase its surface area'. you can really increase
a contact using second, 3th... 4th... wire webbed around. but ' small square of copper' i am not able grasp what
you want to get. nobody making this way - not tesoro not whites not fisher etc.
can you give the pics of inside of coil with it?

[Koala]

[Koala]

Which is the correct wiring connections

I have used the bottom one I suspect the shield should have been between the TX and buck as per top drawing

[WM6]

What about build this one (Wide-scan, DD, 8.5"):


_______________________o TXa
C
C
C
C
C______
C _____ |
C _____ |
C _____ |
C _____ |
C _____ | ______________o TXb
_______|_______
_______|
_______|
_______!____________________|l. Ground (RXa + shielding)
C
C
C
C
C_________________________o RXb

[kt315]

Wm6, in which models of tesoro used this configutation of coil?

[WM6]

Wm6, in which models of tesoro used this configutation of coil?

This suit to (5-pin connector) Tesoro models: Silver uMax, Outlaw, Golden uMax, Euro Sabre II, DeLeon, Cortes

Coil data:

TX = 6.7mH, 20,5E, center-tap

RX = 8,6mH, 22E

[kt315]

thank you WM. forgot i did see it released in Deep Search IV schematic. seems tesoro pulled up their 35 years old tech to light nowaday.

[Koala]

What about build this one (Wide-scan, DD, 8.5"):


_______________________o TXa
C
C
C
C
C______
C _____ |
C _____ |
C _____ |
C _____ |
C _____ | ______________o TXb
_______|_______
_______|
_______|
_______!____________________|l. Ground (RXa + shielding)
C
C
C
C
C_________________________o RXb

TXb is all ready connected to ground on the Bandido. Would connecting the centre of the TX to ground also short out the bucking coil ???? I am probably missing something obvious.