I recently completed three J99 preamps using John Hardy 990cs. All three preamps work just fine except that the gain trim control (R17) on one of the three has a much wider level of gain than the 5db specified in the documentation. When swept fully clockwise, I get so much additional gain that I can go from a very quiet counterclockwise position to ear-splitting feedback when rotated to the fully clockwise position.
On the two other units, the gain trim seems to work just fine--offering a comfortable gain rise from counter- to clockwise. Everything else seems to work fine, and I do not see anything that looks out of the ordinary.
Any ideas?