I'm looking to repair or rebuild a metal detector. It's actually a fairly simple Radioshack model, but it has gotten to where it sounds at all times, even when I hold it up in the air in the woods and spin all the knobs. I haven't used it enough to get that farmiliar with it either. While I know basically how it works with the magnetic exciter and reciever coil, I'm not sure which wire on the coil is which yet. What does this behavior sound like, with it sounding constantly, a shorted receive coil?

Worse comes to worst, this may turn into a resonant comparator. I don't see why I can't detect phase and amplitude shift through the coil(s) to determine what is near the coils. Iron would be one way, copper the other.

 

You'll get better feedback if you supply more details; model, schematic, pictures, whatever you can. Could be as simple as a low battery?

 

throw us a bone mate, model, pictures.....

http://www.hobby-hour.com/electronics/metal_detectors.php

 

It's a relabeled Radioshack (whatever manufacturer) unit. Cat #63-3005. I didn't think about the batteries until Wayneh brought them up, but I still have 9.4 volts on 6 AAs with it sounding. Not sure where to tune it or discriminate it at.

 

I guess I can't post pictures...

 

All I can find so far is the parts list here.

 

No help here... I would like to know technical specs (or at least a wiring diagram) for the search coil. I'm wondering if I have an open.

 

my first suggestion would be shotgun replacement of all electrolytic capacitors.

 

Next up would be a good picture of the PCB.