One of the most common problems with aged Bozak and UREI mixers are the scratchy sounding Alps RK40 black beauty potentiometers. There are several ways to solve the problem and the most commonly used is spray cleaner. This is a quick temporary fix that works for a while but the problem will return. Proper reconditioning for a mixer repair requires more than spray and walk away. This is how we professionally recondition the Alps RK40 controls found in both mixers. Disassembly is tedious and should only be done by professionals who have the required tools.
As previously mention many people use chemical sprays or partially disassemble the original potentiometer. This will temporarily remove electronic noise from controls and partially clean them. Spray cleaning dissolves contact dirt but also dissolves the electrolytic compound grease. This leaves the control with a loose or even physical scratchy feeling. Wear will always be present but the controls can be brought back to a near new condition with complete disassembling, ultrasonic cleaning, and proper reassembling.
We remove the rear shaft clip and complete disassembling all pieces. They are cleaned electronically for 15 minutes with an ultrasonic tank and special electronic cleaning chemicals. This removes all dirt, grease, and residue of any type. The pieces are then wiped clean, heat dried, and ready for reassembling.
The first assembly step is refacing the cleaned shaft with crocus cloth and repacking with silicon grease. This requires special tools but once completed makes the control rotation feel like new. The wipers are checked for worn conditions before they receive electrolytic contact compound. Some wipers extremely worn do not get reused and are discarded. The part’s are assembled, a new shaft clip installed, and grease applied to the rear cover. Once completely assembled the control is ohm tested for accuracy before being installed on a mixer. Photos to soon follow.
