The customer had just purchased this keyboard and wanted it serviced as there was a lot of lint and slider gasket debris in the controls. The work order was to strip out the old gaskets and replace them with felt, clean all old debris from controls and circuit boards/case, lubricate the controls, and replace the battery. To back-up the patches prior to battery replacement (3.6v Lithium from Jameco) I brought an old cassette player into service, and it worked like a dream! Thick (3mm?) foam of the type originally used could not be found, so we went with the most rigid felt that could be found. Felt is not as rigid as the foam, so a lot of double-sided tape had to be put around the controls to hold it. I would not recommend felt due to its lack of rigidity and shedding, but until a better material can be found then we are stuck with it! The unit looks really nice, and the customer was delighted!