Garrett SeaHunter coil onto Crossbow Classic

[TowySalmon]

I would like to use a Garrett SeaHunter 10"x14" mono coil on my Crossbow Classic. I recall that the plug on the coil has to be changed, but I have no idea which wire goes where on the new 5 pin plug.
A local electrics guy will do it for me as I am so ham fisted with a soldering iron.
Can someone help please?
Regards,
Rog

[coinfarmer]

Are all 5 pins used?

If its a mono coil, use an ohmeter to identify the coil pair on both the old and new coil.
Open up the crossbow to identify the shielding/ ground connection.

[TowySalmon]

I have now got a Garrett Sea Hunter 10"x14" mono coil. I am technically challenged, so please bear with me. I have opened up the coil plug on the Crossbow, but I do not know what "to identify the coil pair on both the old and new coil" means. I have though taken pictures. If I were to post them, would that help you tell me what to do?
I have not finished taking the Garrett plug apart to show the connections as I do not know how to take off the last part marked in red. I had a go with multimeter, please see result in drawing.
I hope this is ok for my first step?

[Carl-NC]

As I recall, the SeaHunter mono coil is not really a mono coil. It has separate TX and RX coils laid on top of each other. I think they have the same inductance and resistance, can't recall for sure.

On the connector, I would expect the part circled in red to be a rear shell that either screws onto the front piece or has a bayonet connection. At least, that's how many connectors are made. You could always just cut the connector off, but first make sure the Crossbow can accept a split coil.

[TowySalmon]

Thank you Carl. I've read on here that George has used the same coil on the Crossbow, but the technical side of how to is above my head at the moment.
I will try to take apart the Garrett connector. Failing that I will cut it off and investigate the inner cables.
I also had a play with the multimeter on the Crossbow plug poking the probes here and there and I don't know if I am right path but 1+3 = 1.7 ohms and 3+5 = 1,7/8 ohms....my hands were shaking though. I have pictures of inside the end plate of the control box and the connections to the other side of the 5 pin connector. There are two resistors there too.

[Qiaozhi]

After much searching, I managed to find these scribbled notes on the Garrett SeaHunter coils.
These notes were from January 2012.

[TowySalmon]

Thank you so much for taking the time to find your notes.
I have sent you a PM.

[TowySalmon]

I have had the 5 pin plug fitted by local electronics repair shop (£40, is that a fair price?). But the detector did not behave as I thought it would. Testing the continuity, all the pins are connected and I suspect this is wrong as pins 1,2 +5 are supposed to be linked and 3+4 are supposed to be connected together so I am guessing there is an issue? I may be wrong of course due to my lack of tech' savvy. I took the coil back to the shop and I was bamboozled by the tech' speak of the owner to explain what I found but he said he would check it tomorrow. He asked what the resistance should be between certain pins.

I have found those values for the 8" coil on this forum but not for my 10"x14".

Can someone help with the values for my coil please?

Thank you,
Rog

[Qiaozhi]

HI Rog,

I think the confusion here is that the connector on your Crossbow detector is wired differently to the PDF in post #6.
I believe that you have two different values of damping resistor (470R and 680R) to suit two different coils.

You coil connector should have a 470R resistor between pins 4 and 5, and a 680R resistor between pins 2 and 5.
In the coil plug, the screen should be connected to pin 3, and the centre core connected to pin 1. Also pins 1 and 5 are connected together, either in the coil plug or on the coil connector. I cannot recall which.
To connect either the 470R or 680R damping resistor, you need to connect pin 3 (in the coil plug) to either pin 4 (470R) or pin 2 (680R).
The Garrett Sea Hunter coil needs to use the 470R damping resistor.

The important thing is that the two loops in the Sea Hunter coil must be connected in series and in phase to create a mono coil The final inductance will be close to 500uH.
The connection between the two loops should not be connected to the coil plug.

[TowySalmon]

Thank you George.

The two resistors are at the back of the 5 pin plug on the control box housing.

From “In the coil…….. I am totally at a loss! I’ve no idea which of these: Orange, White/Orange, Blue, White/Blue is the ‘screen’ and which is the ‘centre core’. They all look the same. The cable is not like a coax, it has 4 single strand.

And it just gets worse after that! Its all above my head. None of it makes sense as I do not have any idea what the terms mean.

I’ll go collect the coil tomorrow and just bin it and revert to original coil.

Just wish I had not started this as its all too complicated.

[Qiaozhi]

I've send you a PM.