[rfeenstra]

The hardened build up is probably the original lubricant that they used on the bearings and the grounding wires. I'm not sure why it is so black. I've always wondered if they mixed some powdered graphite into the grease to help with grounding. I have been experimenting with that myself. The problem is, it takes a pretty high concentration of graphite to get any conductivity in the grease. then it's more of a paste than a grease. I've been using that on the grounding wires/springs on the last couple of radios.