They can be taken apart and cleaned up. Do it over a white towel and be very careful of all the contact strips. balls and springs.

If you want, you can use Radioshack Contact and Tuner cleaner, aerosol with a tube, in the crevices without disassembly.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)