Before sending it to the bone yard:
What Compass "gold machine" do you have? My guess it is the Gold Scanner. (The AU-series used a 9-inch eliptical DD) However, all of the Compass Gold machines; Scanners and AU's were all manual ground balance VLF detectors with VLF discrimination available. They could be quickly "bobbed" to ground balance in autotune.
Possibly, your machine is repairable and can be updated. (But maybe not worthwhile.) Keith Wills at "brokendetector" can repair any Compass--- even if run over by a truck(grin). You have posted on the Compass forum. Just go back into the forum archives and you will find posts that may be helpful. Also, Steve Goss at Compass can repair.
To let you know; while the Compass line-up has been available for years, Compass had the "top" designers--- they are still on the cutting edge and designing searchcoils and detectors--- at Compass they were years ahead of their time. The DD and autotune are some of Compass firsts. However, if you have the Gold Scanner Pro (it has an awesome ID meter and two bonus "slide switches" available in the small plug hole at the back of the instrument case) it was on the cutting edge and still could be worth spending a few $$.
Both Keith and Steve are busy. So get an estimate on $$ (include update "mod") and the turn around time for repair. If both the 8 and 10-inch coils are not doing the job; most likely it is in the control box.
But first peek inside the battery trap door. By any chance is one of the spiral wires touching another terminal? And make sure each ot the 3-volt batteries are fully charged with the correct polarity.
However, it could be worth checking out by Keith of Steve before sending to the boneyard. If not fixable
or too expensive to repair, they may be willing to give you a few $$$ for it as "parts."
