My friend DeoxIT D5 would be your best friend!!! for scratchy switches, which sounds like at dusty switch issue.
Sansui servicing
I purchased a G-9000 back in '78 and I'm looking for guidance on how to pick someone to refurbish it (it still works, but has scratchiness in switches). In another thread someone mentioned Dewick Repairs, but it appears he isn't working on Japanese products any more! Anyway thanks for any advice given.