F4 and threshold/ground balancing

[back2thehunt]

I don't know if I have a defective unit but I cant seem to properly ground balance my F4. The manual says that pressing the Threshold + or - can adjust the audible hum in all-metal mode (obviously). I get no adjustability when in all metal mode and trying to GB.

What I do get is a very loud threshold that I can 'contain' by adjusting the sensitivity. I get a very staccato, broken, loud and unstable threshold.

I recall mention of some F4's being sent back to Fisher. Is this the reason why?

Someone with some F4 experience please help! Am I doing something wrong? It seems to be a great machine so far except for the GB issue.

 

[kran0625]

I,ve had my F4 for about four months now. The first couple of times I had it out I could not figure out why the threshold was loud and erratic and the Threshold - pad didnt lower the noise level. Finally figured out that when you turn on machine, rotate the ground balance knob all the way clockwise to preset, press the Auto Tune button. Now when you are getting the loud threshold noise lower the SENSITIVITY a couple notches until you get much quieter threshold. Now the Discrimination / Threshold + or - pads can be adjusted up or down to acheive slight threshold and you can the finish ground balancing procedure. After I have finished ground balancing I am then able to switch to DIsc or all metal mode with Disc mode button and I can raise the Sensitivity up and my machine runs very quiet. I have found that this machine has excellent depth capabilities-better then a couple of my more expensive machines. Also very easy to pinpoint with the larger DD coil. Excellent machine for the money. Good luck and HH.