Cibola Question re: Threshold/GB Mod

Modded Cibola question,

I have a GB modded Cibola and have a question on the threshold pot function. It seems as though the threshold pot is intermittent. That is, when I attempt to set a steady audible tone with the pot, the only way I can get it to maintain the tone is to apply lateral pressure to the knob. If I turn the pot, I get no response unless I push it with my finger. Therefore, in order to GB I must apply pressure to the knob whilst I move the coil up and down. It seems to balance this way and otherwise performs OK.

This leads to another question. When in all metal, am I supposed to hear a constant steady tone as set by the threshold pot and listen for changes? I purchased the detector new (my first detector) last year and never had much success with this method. The detector, when in all metal, is silent and responds when over a target, not constantly humming and changing when over a target. Is this correct?

Also, I get about 4 – 5 inches on a clad dime in an air test. For those that have experience with this detector, is this about what one should expect?


Thanks,

Pete

I didn't have the GB mod on my cibola but I know someone who did. With the detector switched into all metal mode, and sensitivity turned all the way up, you should hear a nice, even threshold hum when you turn the threshold knob clockwise. Once you've gotten to that point, position the coil so that it is 6-8" above the ground. Begin to slowly bob the coil up and down. The tone may get louder or quieter. As you continue to bob the coil, adjust the ground balance until the tone stays the same in both positions (up and down). Make sure that you are not over metal when doing this. If your detector is working properly, you shouldn't be having problems getting a even (non-intermittent) threshold hum. Also, try air testing in disc mode with disc set on iron, sensitivity on 10, and threshold turned all the way clockwise. You should be getting twice that distance in an air test.

Having to apply pressure to the Grnd Bal pot/knob.......is a sure sign of error. Sounds like the 'wiper' portion (internal component) of the pot is/has gone bad.

I agree with Tom......its physically compromised. When you replace it. Spend a few bucks extra and get the best quality available. Since its an important component to your setup.

and what you describe is all on account of the threshold pot being bad..not the G.B. mod causing it...

in all metal to get any depth you will need to have the threshold working...when it';s disabled it is out fo the circuit and the depth suffer's from it...try a test when in all metal push the pot til it start's working and the depth should be substantial if you set the thresh right...

it could just be some dirt on the pot or the pot wiper is not making contact...

probably the later..


It should be a simple fix...the threshold pot is 100K on the Cibola....if you can use a soldering gun and unsolder 3 wires and solder them back in the same order on the new pot your problem will be solved I am sure...

get a nice pot there the small size 1/4 " thread short shaft....don't go to radio shack they only have the large size... order one that's the smaller size like the one inside your's..

they are all over e-bay... here's your's make sure it's linear taper.

.[cgi.ebay.com]

Keith

Thanks for the info Keith. I was concerned I may have mucked something up with the mod. I'll pick up a new threshold pot and give it a try. What should I expect for a clad dime air test on the modded Cibola??