That’s strange. Turning GRSCALE should definitely result in a change, also at the QBIAS voltage you are getting.
Yes, you were measuring the right spot.
Are your FETs matched? The QBIAS setting puts the compression FET into slight conduction and is different for each FET. For the GR meter circuit to show the correct amount of compression, the second FET needs to be matched to the first one. When idle, the QBIAS voltage gets added through the second FET & the GRSCALE trimmer to an offset provided by GRNULL.
Can you post a high resolution photo of the complete right hand side of the stuffed board (the one with the comparators and U10)? Maybe I can spot something that’s not quite right...
Yes, you were measuring the right spot.
Are your FETs matched? The QBIAS setting puts the compression FET into slight conduction and is different for each FET. For the GR meter circuit to show the correct amount of compression, the second FET needs to be matched to the first one. When idle, the QBIAS voltage gets added through the second FET & the GRSCALE trimmer to an offset provided by GRNULL.
Can you post a high resolution photo of the complete right hand side of the stuffed board (the one with the comparators and U10)? Maybe I can spot something that’s not quite right...