No continuity on Tx side of a Nel big coil question.

[kac]

I have a Nel Big coil for my AT Pro that had lost performance. Out of curiosity I compared the impedance and resistance with the stock coil:

Stock:
Tx 9.61uf/31.7Ω
Rx 3.87uf/5.2Ω

Nel Big:
Tx 4.7uf/0Ω
Rx 3.73/6Ω

Putting a meter to check continuity all my coils have a tone across Tx or Rx but the Nex Big has no continuity on Tx.
I checked the cable and connector and all is in good shape, no scuffs or kinks. There are no cracks in the coil epoxy and the coil has fairly low hours on it.

I also checked continuity with swapping + and - thinking maybe there was a diode inside but made no difference.

Coil still sort of works which is puzzling to me but performance is pretty poor. Low depth and targets don't lock on. Possible there is a bad tuning cap or solder joint inside that went bad?

[Skippy]

You've narrowed it down to the TX correctly, which helps diagnosis.
The most likely failure point is the connector. Second most likely is the cable, close to where it enters the coil.
Wiggling the cable at these two points may give a fault indication. With the machine powered up, you would get false signals. With a test meter checking resistance, for example, the resistance would vary.

[kt315]

microFarade or what units?

[kac]

microhenry, forgot to mark on in my message.
Tested the cable to see if there are any breaks and cable seems pretty solid. No fluctuations at all. End where it connects to the control box is epoxy sealed and epoxy has n cracks or flaws.

Starting to think something died internally.

So my guess is Nel uses a fixed set of winds on their coils and tweak them with tuning caps to work with different machines so only changes is the cap and cables? That sound about right?

May use the cable and see if I can make a small coplaner for the AT Pro.

[Carl-NC]

I assume you mean mH, not uH or uF. The measurements look backwards, the TX coil will be the lower inductance & lower resistance. So it might be the RX coil is bad. And do you mean to say the bad coil has 0Ω or that it is open (R=∞)?

It's possible a connection has broken but is still close enough to get capacitive coupling that allows some signal to get through. I would start by opening the connector, see if a wire broke loose. If it's not there, then it will either be in the cable or in the coil housing.

No, NEL would certainly design their coils specifically to match the factory specs for whatever model is intended.

[kac]

Meter said uF. You're right it is Rx side that is bad. Cable is in excellent shape and connector is epoxied under the nut with no signs of damage. Wiggling or tapping on cable anywheres makes no difference so can only assume the connection failed inside the housing.

Anyone know offhand if Garrett does anything special with their AT Coils internally? IE tuning caps etc. I was thinking it is wired similar to the Tesoro Delta coils?

Thanks for all your help.
Ken

[kt315]

can you give a link on your tester? also, what its range you measure in?

[kac]

https://www.sainsmart.com/products/d...nSmart+Catalog

They are pretty much automatic.

Continuity I used a regular meter.