Jimmy tdi dual field mono

[toga]

I was hoping someone could answer a couple questions for me.
I purchased a Jimmy tdi dual field mono eliptical coil when I bought my TDi detector. I used the stock round coil for a while, and the detector worked well. When I switched to the Jimmy, after a while my ground balance stopped working so I sent the unit back to Whites and they repaired it. Then shortly after the ground balance stopped working again and I sent it back in. This time they said my Jimmy coil was bad, and sent me a 7.5 round coil as a replacement, as well as my Jimmy.
Does anyone have an idea what in the coil is defective that would cause the ground balance to stop working? and if I can repair that coil myself?
Thanks

[toga]

I have one other question....
I noticed that the connector has 5 pins, and these coils that people are building have two wires coming off them. What are the other three connections for? (I'm a noob when it comes to this, any help would be appreciated)

[Reg]

Any time your detector seems to quit working right, it is a good idea to try another coil if one is available. The reason is simple, the coil is what takes the most abuse.

Now, with that said, have you tried your Jimmy coil since your detector was returned? If so, what does it do or not do? If it doesn't seem to ground balance, try passing your hand over and under the coil and see if you can detect your hand. Also, bump the coil with your hand slightly and see if it makes noise. If it does any of the things mentioned, then something isn't right.

The logical thing to go bad would be the connection to the shielding is not functioning or functioning correctly. However, the Jimmy coil has two windings and one of those has a resistor across the winding. If that resistor has gone bad, it could cause strange things to happen also.

As for the connector, only two wires are used on a mono coil and the Jimmy coil is a form of a mono coil. The other connectors are used for a dd coil.

Now, there should be a jumper in the connector, connecting pins 2 and 4, and maybe 1 and 5. Pin 2 is the receive pin and pin 4 is the transmit pin. Since the coil is a mono, the transmit and receive have to be connected and this is done with a jumper inside the connector between the two pins mentioned.

As for taking it apart, that can be done but does require patience. I haven't looked inside a Jimmy coil closely so I can't explain what to look for, but I will say there will be a heavy coating of conductive paint (shielding) on the bottom and top halves of the housing. So, there needs to be some type of connector connecting this shielding to the shield wire of the coax. Make sure that wire or any other part of the connection hasn't broken.

If you decide to take it apart, take your time and take pics of the inside so you know just what it looks like in case you have to put it back together you will know where things go.

Reg

[toga]

Thanks Reg for the reply, information and suggestions.
I tried the Jimmy coil and everything seems to work fine... I bumped it on the ground as I was balancing it, and it didn't make any difference.
I'm going to use it for a while, and when it stops ground balancing again I will switch coils and see if that solves the issue. Then I can confirm its the coil that's causing the problem.
I will post my findings when I can get it to duplicate the issue.
Thanks again,
Mark