The Crossbow Classic PI

[eclipse]

Don't go for Wirewound type resistors, use only Metal Film/Metal Oxide types, at least 2W as Qiaozhi said.

[6666]

Two x 2 watt to make up what value you need, or even 4 x 1 watt to get the power and value.

[TowySalmon]

No idea about different types of resisters, sorry but I have, liked mentioned before, not an electronics expert.
But, I have installed a 470R resister between pins 2 and 4 inside control box this morning.
I then as a control, connected up the original coil and it works, so I haven't broken anything.
I then connected the adapter, then the new coil. Switched on and get the correct (I presume) threshold and nothing is detected even an inch from the coil, no change in threshold whatsoever!
Removed the adapter and connected the new coil direct to the control box. Threshold clicks present. A metal object will change the threshold up to 3" away.
I believe, that this shouldn't happen as as far as I understand it, the resister is essential so is the adapter. So what's going on p[lease experts as I am getting very frustrated.
Currently at the back of the coil plug inside the control box, I have as stated, the resister between 2 and 4, an orange cable to 3, a blue cable to 1 and a yellow cable to 5.
Is the installation of the resister the only part of this modification?

[Qiaozhi]

But, I have installed a 470R resister between pins 2 and 4 inside control box this morning.
Currently at the back of the coil plug inside the control box, I have as stated, the resister between 2 and 4, an orange cable to 3, a blue cable to 1 and a yellow cable to 5.
Is the installation of the resister the only part of this modification?

It sounds like you forgot to add the two links in the adapter cable between pins 1&2 and 3&4. Otherwise the damping resistor isn't actually connected to anything.

[TowySalmon]

Sorry, but as I wasn't told to do it, I didn't, despite my pal saying he thought those two connections needed doing after looking at the schematic.
After connecting 1&2 and 3&4 will the use of the adapter be necessary?
Will do the above connections tomorrow, or rather pal will as I am not very good with the iron.
Thanks again.
Picture of resister used. It wouldn't surprise me if I have used wrong type.

[Qiaozhi]

Sorry, but as I wasn't told to do it, I didn't, despite my pal saying he thought those two connections needed doing after looking at the schematic.
After connecting 1&2 and 3&4 will the use of the adapter be necessary?
Will do the above connections tomorrow, or rather pal will as I am not very good with the iron.
Thanks again.
Picture of resister used. It wouldn't surprise me if I have used wrong type.
[ATTACH]40938[/ATTACH]

The resistor pictured is fine.
The connections between pins 1&2 and 3&4 are shown in the "Minelab DD Coil.pdf". These need to be done in the adapter cable plug (as shown), not the coil socket in the back of the electronics enclosure. If you put them in the coil socket, then the original coil will not function correctly.

[TowySalmon]

I obviously cannot read the schematic. To my eyes and common sense, the connections to 1&2 and 3&4 are to the left of the adapter, which is to my way of thinking, the plug inside the control box. But hey ho. I will get pal to connect 1&2 and 3&4 on the plug that is at the end of adapter that connects to control box.

Also!!!! I think I mentioned this previously, everything connected to all. The schematic shows the GPX coil plug as having continuity between 1&2, 3&4, 4&5.
On my coil plug, it's 1&2, 1&3, 1&4, 1&5, 2&1, 2&2, 2&3, 2&4, 2&5, 3&1, 3&2, 3&3, 3&4, 3&5, 4&1, 4&2, 4&3, 4&4, 4&5, and yes, you've guessed it, 5&1, 5&2, 5&3, 5&4,
So, I won't be putting any money on things working tomorrow.

[6666]

It is for the GPX, GP, SD series: https://detech-metaldetectors.ro/en/...lab-gpx-series

I do though fear that after doing continuity that something is not right...........?

What exactly is written on the coil label ?

[6666]

I obviously cannot read the schematic. To my eyes and common sense, the connections to 1&2 and 3&4 are to the left of the adapter, which is to my way of thinking, the plug inside the control box. But hey ho. I will get pal to connect 1&2 and 3&4 on the plug that is at the end of adapter that connects to control box.

The pins should have numbers beside them on the plug front and back, so the pin number is the same weather you are looking at them from the front or back of plug.
The plug is also a 5 pin microphone plug NOT a 5 pin DIN.

[Qiaozhi]

I obviously cannot read the schematic. To my eyes and common sense, the connections to 1&2 and 3&4 are to the left of the adapter, which is to my way of thinking, the plug inside the control box. But hey ho. I will get pal to connect 1&2 and 3&4 on the plug that is at the end of adapter that connects to control box.

Also!!!! I think I mentioned this previously, everything connected to all. The schematic shows the GPX coil plug as having continuity between 1&2, 3&4, 4&5.
On my coil plug, it's 1&2, 1&3, 1&4, 1&5, 2&1, 2&2, 2&3, 2&4, 2&5, 3&1, 3&2, 3&3, 3&4, 3&5, 4&1, 4&2, 4&3, 4&4, 4&5, and yes, you've guessed it, 5&1, 5&2, 5&3, 5&4,
So, I won't be putting any money on things working tomorrow.

OK - let's see if I can make this a bit clearer. Please see modified PDF attached.

In the bottom diagram, everything on the left of the adapter cable is in the Crossbow enclosure, and everything on the right of the adapter cable is in the Minelab coil connector. The connections shown in the middle (between the right and left connectors) are in the adapter cable. The idea of the adapter cable is to connect the Minelab TX and RX loops to the correct pins on Crossbow, and to connect the damping resistor in the enclosure across the TX loop. When the adapter cable is disconnected, the resistor is out of circuit. If you then connect the original mono coil (obviously without the adapter cable), it uses its own internal damping resistor.

Hope this makes sense.

[TowySalmon]

Hi all,
Well, we installed the jumpers between 1&2 and 3&4 at the box end plug of adapter and checked the connections twice with ref' to the diagram. Funnily enough, I had coloured the connections on drawing very much the same as your revised .pdf. The correct plugs have been used and the layout of pins is now imprinted on my brain as I have looked at them through a magnifying glass so many times.
So, picture of coil label and for interest my coloured lines on drawing.


And did it work when we attached the (finally) correctly made adapter? No. There is no response from the coil whatsoever?

[Qiaozhi]

Hi all,
Well, we installed the jumpers between 1&2 and 3&4 at the box end plug of adapter and checked the connections twice with ref' to the diagram. Funnily enough, I had coloured the connections on drawing very much the same as your revised .pdf. The correct plugs have been used and the layout of pins is now imprinted on my brain as I have looked at them through a magnifying glass so many times.
So, picture of coil label and for interest my coloured lines on drawing.
[ATTACH]40952[/ATTACH]

[ATTACH]40953[/ATTACH]
And did it work when we attached the (finally) correctly made adapter? No. There is no response from the coil whatsoever?

Whereabouts in the UK are you located?

[TowySalmon]

I have replied via PM.
Thank you.

[6666]

Dont leave us in suspense we are all dyeing to find out if this was fixed and what was the problem with the wiring ?

[TowySalmon]

A huge thanks to Qiaozhi for all his time, patience and expertise. A thank you too to all the others here who have contributed their help.
The Crossbow now works with the new coil, but I do not have the knowledge to explain what the problem with the wiring was.