Thanks for all of your posts on cleaning Phenolic a fretboard. I was a bit nervous about using any compounds, including WD40, so I tried a cloth wet with a little water. It seemed to clean off the grime just fine.
I may try a little WD40 on one spot and will report back.
I am in the process of cleaning the whole instrument and re-doing the dead electronics of the 1980 Kramer XKB-20 which I bought a month ago. Don't worry, I am only replacing the corroded tone and volume potentiometers and capacitor, properly shielding the whole cavity and cutting the bridge (shocking) wire. The original Dimarzio split P pickup is being kept because it still kicks as well as any pickup could.
I'll post pictures after I get it all refurbished. It's going to look like a shiny new bass, except for 4-5 small dings in the wood.
Thanks again.