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Overloading Coil Issue


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I'm new to this forum and was pleasantly surprised at the number of knowledgeable members here. Hopefully someone can help diagnose my coil problem. I have two M6's, both about 12-13 years old and have the 9.5 coil and the 4x6 shooter coils. One has less than 10 hours use and the other has 100's of hours use.  The most used one had been unused for a few months and when I took it out with the 4x6 coil, it overloaded immediately when I turned the sensitivity level to max. I always run it that way. I took the other (barely used) 4x6 and put it on and same thing. So I took the other M6 and tried both 4x6 coils on it and they overloaded as well. The 9.5 coils have no issues. I took the metal detector to a different location to rule out possible EMI and the same overload issue. After using the detector with the 9.5 for a few weeks I put the unused 4x6 on it and it will work for a while 40-45 minutes and then overload. The heavily used 4x6 won't work at all at high sens. It's got me stumped.

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I’m fairly sure that some 4x6 Shooter coils had a history of overloading across different Whites detectors but don’t really know much else. I think the “V” rated coils didn’t have this problem?

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2 hours ago, Tony said:

I’m fairly sure that some 4x6 Shooter coils had a history of overloading across different Whites detectors but don’t really know much else. I think the “V” rated coils didn’t have this problem?

Yeah, I have read that the V3 had to have them. All I can figure is there must be a 'shelf-life' on them being that the one with so little use is doing it too. I better go ahead and purchase a couple x-brand coils before the companies stop making them for White's detectors. It's going to be a sad day when I can no longer use my M6's. After so many years we speak the same language. Thanks for the reply.

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Hello Florida Tabdigger.

Many moons ago White's had some coil issues regardless v-rated or not. (V-rated is only important if you wanna run the coil on a spectra high gain + boost.) From what I remember that time is, they had a diode for temperature-compensation inside the coil that was causing some trouble after some time. But they swapped out those coils to the users for free.

If you're after a very sensitive and deep coil for the M6 I'd recommend the Detech Ultimate 7" DD or the 6x8" S.E.F.

279685579_7inchUltimate_2.jpg.51a04b7ccdb1c214963db2333d624ae6.jpg

 

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There should be no diode. Some coils may have a thermistor but that's not the problem. The 4x6 is a DD coil that is completely encased in epoxy. DD coils are incredibly sensitive to coil movement (concentrics are not) and any movement of the epoxy will knock the coil out of null and cause overload. White's had fits with those coils in production, after the epoxy was poured it was baked in an oven for 2-3 days, then sat for a few weeks to fully cure. Then the final tweak null was applied and the coil was sealed. Sometimes even that wasn't enough and coils would drift months later.

You have two solutions. 1) Don't run it at max sensitivity. 2) Remove the bottom plastic and re-null the coil. For #2 there is a loose winding that is held down with hot-melt. Moving that wire around will alter the null. To do it right you need an oscilloscope, but you might be able to at least make it better by using a ferrite and the detector's overload audio.

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20 hours ago, Geotech said:

There should be no diode. Some coils may have a thermistor but that's not the problem. The 4x6 is a DD coil that is completely encased in epoxy. DD coils are incredibly sensitive to coil movement (concentrics are not) and any movement of the epoxy will knock the coil out of null and cause overload. White's had fits with those coils in production, after the epoxy was poured it was baked in an oven for 2-3 days, then sat for a few weeks to fully cure. Then the final tweak null was applied and the coil was sealed. Sometimes even that wasn't enough and coils would drift months later.

You have two solutions. 1) Don't run it at max sensitivity. 2) Remove the bottom plastic and re-null the coil. For #2 there is a loose winding that is held down with hot-melt. Moving that wire around will alter the null. To do it right you need an oscilloscope, but you might be able to at least make it better by using a ferrite and the detector's overload audio.

So this is info from first hand. The reply I did was from hear-saying by the White's forum...many moons ago.

Thanks for clarifying, Carl.

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