[Robert Stevens]

I recently picked up one of these. The first 3 channels worked well out of the box. The last (4th) channel had some issues with thumping and still doing some gating even in the "out" position.

I was able to fix the thumping on channel 4 with the info in the manual about adjusting the "cntl rej" trimmer on the back of the unit.

I was also able to fix the second problem on channel 4 where the unit was still gating/expanding when in the out positon by adjusting a second trimmer pot inside the unit labeled "cnvtr symn". I, however, see no mention of this trimmer (or the one next to it "dist null") in the manual. They do show up on the schematic and looks like some sort a calibration for voltage dividers.

It would be nice to know what I am doing rather than just blind luck that adjusting the one pot solved my problem.

Finally, that one channel also seems to drop 2db in signal compared to the other 3 channels which drop 0db when in the out position or prior to gate/expansion threshold. Not sure what to look at there.