Why the heck was it necessary to varnish the pot axes?? It is impossible to remove the pot caps without the risk of damaging the circuit board and/or the housing and thus impossible to open the housing.
I left the batteries in and have to fix the corroded contacts of the battery holder to use it with batteries. (which is inevitable for any kind of serious recording due to the USB hum problem, but that's another sad story).
Any ideas?