My C50 Olympus S8R system is now 40 years old and I've removed all components from the cabinets and brought them to a JBL shop for upgrade and repair. I want to refurbish the cabinets as well which are a dark walnut finish. Years ago, I had instructions on maintenance of these cabinets but they have been long lost. Does anyone have instructions on the correct way of refinishing the outside of these C50 Olympus cabinets?