I also acquired my unit used on eBay. After ten years the volume control became touchy and then cut the signal permanently to 50%. My second unit was also from eBay and came with the control already a bit touchy. One observation about the AR sub is that in a port-to-front position it was weaker (per my room configuration). Turning it 90 deg away from front made it perform gangbusters.
I have a vintage AR 12 inch subwoofer in excellent condition, except that the level control is spotty. Is the pot for the volume level control a sealed housing or can it be sprayed with contact cleaner?
I have a vintage S112PS subwoofer that needs to have the pots cleaned. Photos showing the electronic plate disassembled do not show original sealing material on removal. Does the electronics plate remount need a bead of sealant or does design preclude the need to seal this plate? Has 8-10 screws against cabinet.