What can cause a detector to maintain its threshold but lose the ability to detect targets?

[michaelnc]

I'm curious because I have a detector that does this on occasion. I do not want to send it in for repair because I can't afford to right now and it isn't under warranty. Does anyone have an idea what can cause this and a possible fix without having to send the detector in for an expensive repair. All I have to do is tap the control box and it starts working again but this is very annoying after you have detected for several passes with no target sounds and then realize it has lost the ability to detect a target.

 

[Ism]

WAG....wire in the box going to the coil connector. I have removed the coil from a couple detectors and still had a threshold when I turned it on. It was accidental but never hurt the detectors.
If you feel up to it, take a look inside for a broken wire at the solder joint on the connector or the circuit board. It might even be your coil connector or a broken wire in the cable near the box.

 

[BarberBill]

Ism may well be right on. I've had a similar result with a manual ground balance machine when the balance was way, way, off.
BB

 

[michaelnc]

I noticed that the detector does maintain a threshold even with the coil removed. So I assume this would mean the connector at the control box has a loose wire inside. I guess I don't have a choice but to send the unit in but I'll have to wait due to lack of funds.