tkr, Are you sure your problem was like that described by the OP? Because his problem does not at all sound as simple as a grounding problem really is. What he describes seems most likely due to a bad solder joint or a defective diode or transistor or op amp, somewhere.
Believe me, this was an earthing problem like I`ve never had before. There was popping, crackling, spiking.
I had a Manley repair contractor come home to me, after having sent the unit away for repair TWICE. Only then was the problem solved.