I talked with Rusty before sending the detector in, so he knew what model it was…also, it was the ground balance control that I was having trouble with.
When I got it back it worked fine, but he told me one of the coils failed while tuning or checking and they sent me a new coil along with mounting hardware.
He even enclosed a detailed hand written note….
I believe the ground balance pot on a fixed ground balanced model can be adjusted to actual ground contritions, but is not intended to be adjusted a lot.
I am not sure what is involved with tuning the coil, but I remember seeing that quite a few people were sending them in to be retuned… of course this was when the service was free too.