Coil repairs info

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Coil repairs info

Post  deutran on Thu Nov 02, 2017 9:38 am

I'm just wondering what glue and graphite paint others are using when repairing their coils.My first repair on the 8"minelab was very successful it is rock solid.
I used MEK for the housing which I gather is ABS on the commander.Seems to work well I used the blue one but can get it in clear as well.As for the graphite shielding I used a graphite rod and filed it to a fine powder and mixed it with acetone,worked really well.For the shielding wire I bonded it with hot melt glue in a few spots then used a thick mix of the graphite and then glued over it with epoxy then masking tape over that got a good result which shouldn't separate.
As for the shielding I didn't want too much just enough to keep it reasonably quiet as it turns out its ok but on the next coil I might add just a little more.
The resistance of the original was about 10 ohms per cm.
The cable entry point through the urethane base was strengthened with hot melt glue as I notice the cable was slightly twisting if it got caught on sticks etc it would move the shielding wire.The shielding wire was also re-routed to avoid this.
My next coil to repair is a Coiltek 14"mono terracotta as this was a favourite and got a bit noisy over time.Found a lot of gold with this coil so repairing it is definitely worthwhile.Might document this one.
Steve
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Re: Coil repairs info

Post  UNCLE BOB on Thu Nov 02, 2017 1:27 pm

Hi Steve,
Do you have any warranty left on the coil?
If not, it's always good to ring Coiltek and talk to them about your coil.
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Re: Coil repairs info

Post  colour on Thu Nov 02, 2017 3:29 pm

Hi all

I've recently repaired my 11" coiltek elite mono - pick handle dropped and cracked the plastic and damaged the shielding. Repaired the crack with black ABS plastic mixed with acetone. The ABS glue texture should be equivalent to pancake batter.

As for the shielding, I first tried Mylar film which worked good for a short while but very hard to get a good connection with the ground wire.
Found it hard to purchase graphite paint locally or on the net, but researched that few have used nickel conductive paint with good results. A 400ml spray can will cost between $35 to $45. Sprayed it on thin cardboard and epoxy glued it on the foam base that holds the windings. It only needs a very thin layer with even conductivity throughout the surface. If the shielding is too conductive it will be sensed by the detector - mine where about 50ohm. When spraying nickel conductive paint, wear a mask in a very well ventilated area. Before spraying, give the can a good shake for about 5 min.

You can use steelo wool and lightly remove any access nickel. Make sure nickel paint dust does not get into the coil shell as it is magnetic. Don't apply shielding all over, just securely fixed the shielding to the top and bottom with a gap between the two layers and that the ground wiring is securely fixed to both layers.

As for performance and stability , it still works great as before except that it's not touch sensitive anymore.

Happy hunting.
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Re: Coil repairs info

Post  deutran on Thu Nov 02, 2017 7:10 pm

UNCLE BOB wrote:Hi Steve,
Do you have any warranty left on the coil?
If not, it's always good to ring Coiltek and talk to them about your coil.

Coiltek have always been excellent on their service and I'm sure they would fix it but I want to improve on the original build and make sure the repair lasts.
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Re: Coil repairs info

Post  deutran on Thu Nov 02, 2017 7:11 pm

Thanks Color some good info there.
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