Compass AU-52 Coil

[lytle78]

I have a compass AU 52 with a bad coil. I've tried to find someone who can repair it and I think I've tried all the known sources – unsuccessfully. There is a sort of rumor out there that whites Goldenaster coils could be modified to work on this 52 kHz detector. For example This was posted on the compass forum couple of years ago –

"I had read of an article somewhere (I can't recollect where) that quoted J.E. (John Earle) stating the Whites GM coils could be rewired to fit the older AU Scanners. Now how, sorry to say, I don't know".

I'm also told that a couple of years ago someone talked to John Earle about this and he said frankly that he could not recall if such a thing had been done or if so how.

Does anyone out there know anything about this and could you enlighten me? There is some hope that there someone who can manufacture coil for this and I'm waiting patiently to hear back on that subject. In the meantime any information anyone has to be most welcome.

Rick Kempf

Gold Canyon Arizona

[Qiaozhi]

I have a compass AU 52 with a bad coil.

What is the problem with the coil?

[lytle78]

The detectors been checked out okay. It won't ground balance however. At Max plus ground balance it still too negative – goes quiet as the coil nears ground. Also noisy when tapped up against anything.

[Qiaozhi]

The detectors been checked out okay. It won't ground balance however. At Max plus ground balance it still too negative – goes quiet as the coil nears ground. Also noisy when tapped up against anything.

When a coil becomes noisy when tapped up against something, or chatters in wet grass, it's usually an indication that the shield connection has become detached in the coil.

However, since it won't ground balance, it sounds as if the coils have moved out of alignment. In your photos the coils seems to be secured with hot glue in only a few places. It might be worth trying to adjust the coil overlap to see if ground balance can be restored.

[Merc]

The Garrett elliptical that I worked on looked very similar. It was secured in epoxy as well except for a loose loop of wire. The loop was moved around to do the final fine tuning and then secured at the factory. The Garrett coil had the tuning loop secured with masking tape which apparently does not last forever. Anyway, it doesn't take much movement at all to throw off the ground balance. I had another good coil to compare with or I would have never got it right. If your tuning winding has moved you may have to have access to a known good coil to compare to. In my case I had the target ID of my GTA1000 to check it with. I tweaked the circuit pots until the ID was correct on the good coil(needed because I had moved them before trying to find the problem without a good coil) and then swapped to the bad one and made very slight changes in the loop position until I had it right and then glued it down. In your case, if you want to try, get the known good coil, pick a small piece of metal that you can discriminate out; pulltab, zinc penny, whatever. Make note of where on the dial it discs out. Put the bad coil on, move the tuning loop and when you get the disc to occur at the same place, you should be really close. Just my 2 cents.