This Studiomaster Trilogy 166, came to us for a service.
The pots were stiff and some of the channels were cutting out.
Well put together, each channel has its own pcb, all of which are then daisy chained.
I started by removing the knobs and nuts from the pots.
Then 1 by 1 unsoldered the pots, cleaned them and put them back.
Inspect the board for dry joints, mainly around the input jacks.
These are the pots from just 4 of the boards
Re-assemble the unit and test.