Older Tesoro Lobo Not St ...help

[jeff_jones_86004 0]

Got a used Tesoro LOBO, but with or without coil, it just screams when I turn it on. Adjusting threshold no help. Any ideas, or anyone need it for parts?

Thanks,

Jeff in AZ

 

  

[Rivers rat 949]

Did you play with the retune switch??

 

 

RR

[jeff_jones_86004 0]

Not a lot.  What should I try?

 

Thanks,

 

Jeff

[Rivers rat 949]

i had the problem once on another Tesoro threshold was drifting 

[jeff_jones_86004 0]

So how did you fix it?

 

 

[dirtman 159]

I'm not positive, however I was under the impression (especially with P.I.'s)  you shouldn't turn on ANY detector without the coil connected.
?????  Could be a problem there.
 

[Rivers rat 949]

Hi it was on a modded silver sabre 2 this machine has more knob and switch than anything.What i realise is when warm(no joke) it works ......plug the coil and try again to turn all knob and switch.I got 2 LOBO ST and the scream when turn ON to indicate the battery level.But i am unfamiliar with the original LOBO

 

RR

[kac 2,907]

With the coil on and fresh batteries, does it still do that with threshold all the way down and sensitivity down?

I never try a machine without a coil, I heard it could damage a machine. Not sure if that is true or not or specific to digital machines but never took the chance.

People are selling lobo boards (remakes) online. I had seen a fully assembled board for around $39.

[Lobo Exp 12]

I cannot say for positive on the issue of using a control box without the coil plugged, but I can say that with other circuits like 2 way radios, it is not a good idea to turn them on without the load coil which is what these machines are, transmitter/receivers. 2 way radios are meant to work with antennas tuned for a low standing wave ratio. Take CB's for instance, there are SWR meters for tuning the antenna length. Ideally you want a 1:1 SWR. Different frequency transmitters require different length antennas. Metal detectors work on the same principle. They send out a electromagnetic wave from one of the coils and the other picks up distortion in the wave shape when a metal object is within the field it generates. The metal object resonates its own field when the electrons in it are excited by the field from the control box signal sent out in the TX coil. So if there is no load sensed by the transmitter, the signal is fed back into the control box and the Integrated circuits are often very sensitive to load and reflected signal. Since that signal is supposed to be sent down a length of cable to a coil which is away from the control box, through a shielded cable lead no less. The coils are designed to have a certain impedance/resistance which changes with changing frequencies. I do know that the higher the power level, and frequency the more it can be a problem. I have been told it is not a good idea to turn on a Microwave oven with nothing inside or metal objects inside, they are high power and so, I think it would make sense not to turn on a small generator such as one of these detectors with nothing to absorb that power as well. 

[Lobo Exp 12]

To Jeff Jones,,, I was wondering if you got rid of the controller you mentioned earlier? I have been working on one of those Russian Federation PCB's for a while now, a little here and there as I can get parts for it. I'm also looking for a coil that is tuned to the frequency this board is running at, 17,5khz. I may give a try at making my own coil, I have some enamel coated wire, but not sure if I have enough to make the coil. Making the form and getting the housing may turn out to be the hard part, getting the proper materials needed for it.