Mine lab coil problem???

[migolddigger]

I have had my MineLab Stock coil replaced for the second time recently. I ask Hann's at MineLab what was wrong with the coil. He told me there was a bump on the bottom of the coil?? I asked him what caused it, and was told a power surge??? I'm not saying Minelab is using Band aids to fix an obvious problem but I thought I'd shoot this by the experts. Here's the back round on my Explorer II. I have returned it to Minelab 4 Times in one year. First time was a bad coil. The second time they replaced the center board. The third time they reseated it. Now they have replaced the coil again. Here's my question. Can a power overload /surge cause a bump in the coil? Does this seem possible or am I getting the smoke and mirrors trick here? It would seem logical to me that they should be focusing on what caused the power Surge or over load. Not just replacing parts. If this was a car I would be getting a new one by now. what do you guys think? let me know.

Thanks Tom

 

[Hard Nosed Dave]

migolddiger,

My thoughts on this.


Yes, a bump might result from plastic melting from the wires, inside and under the plastic because; it has somehow been shorted and received a power surge. The wire that is used in the coil would be one of the thinnest points that if it were subject to say a shorting out within the control box by somehow the positive voltage being sent in to these wires then it would probably make it heat up in a resulting boil at its thinnest point or the points of contact (somewhere on the loop where the enamel has heated up and you get shorting.(Seen it happen in transformers, but never in a metal detector loop.) To calculate that the cause was from a power surge would be difficult as I feel the Explorer internals (especially the power board) would have died first before it were to get as far causing this boil..........in the coil. There are onboard PCB tracks that might cook before the wire loop does BUT this is again dependent on where the point of shorting has occurred. There are other possibilities.

There is a "native" voltage output that comes from the control box connection for the coil when the Explorer is on, but in my opinion NOT enough amps to cause the wire, in the short term to heat up and melt from the inside out to cause such a boil. It would require a higher current output basically directly from some or all of the current the batteries produce OR at a point on the board where this current was present. I can only picture any of coil wires or board tracks shorting to one of these points where the positive current is at it higher end.

Personally I would have demanded a replacement detector, new or old of the same model (Explorer 11) right about the third time. I believe, that provided the consumer, you in this case ahs NOT been the cause, simply because you've used the detector within "parameters" of recommended use and NOT with "abuse" of the product, then you should have rights that most modern developed countries allow for it in their consumer laws. You give the manufacture and or supplier a fair chance to make good and if they don

 

[Cody]

Well, this is a good one. Frankly, a new coil and circuit card is about as close as one can get to a new detector other than including the LCD. It would be difficult for me to accept the bump and power surge explanation but it is possible. I am afraid I would have to take that one up the line. Although, a coil of wire across the power supply with no other DC resistance would create a lot of current. In theory we would have I = E X R where E is the power supply, R is the load, and I is the current. With a resistance of only 1 ohm the current flow generated by about 12 volts would be 12 amps. That would burn the wire and could cause a bump on the coil due to the heat. A surge sounds more like some kind of power being induced into the coil from an external source. It seem odd to refer to the problem as a surge from a DC supply. A surge is more often than not associated with AC than DC but can apply to both.

 

[migolddigger]

Dave and Cody. Thank you for your Reply. I have asked Dick Shults, and Hann's for a new Explorer II or even to depreciate the value of the old one and I would pay the difference, but got denied this. The bump Surprised me because I take good care of my detector and keep it clean. Even before I sent it back, I inspected it for cleanliness and looked it over. The last problem I had was that the Explorer II was hitting on targets real weak. Only when I used Audio 1, Manual 28 or higher, Gain at 10, could I even get a solid signal close to 4-6 inches. Now a friend of mine, Ross Soderberg, let me try his 8 inch coil on a trash infested park, and it seemed to respond the same way. So when I sent it back I expected the findings to be something internal, possibly one of the other boards. There was no cosmetic bulging on the outside of the coil at all. However The coil never really centered targets on the Mine Lab label but more toward the rear of the coil in the center. My previous one that came with the Explorer II centered spot on the Mine Lab label. I did ask Hann's about this issue, and he assured me that this is the problem and that he would send me the old coil as well as a new one. When They both arrive I will do the same inspection on each coil and If I can't see a difference. I will send it to you Cody if you like. Maybe a cross section will show us whats wrong. we could all benefit from seeing what they are talking about at Mine Lab. I'm not trying to push this job on you Cody, if you want I will do it. I just thought I'd leave it to the expert thats all. Thanks again for all your help Dave and Cody, without you guys to answer a neophyte's questions, what would we do?

Thanks again for taking the time to respond.

Tom weaver