I have had my '85 4003 for around a month now, and I wanted to ask the Ric experts if this hum is normal. It isn't over powering, sort of like a jazz bass with one pup soloed. It doesn't change with the pup selector in any position,neck, both, bridge. It doesn't stop when both pups are on and set at the same volume & tone like a jazz bass does. There is no shielding, paint or foil, in the pup cavities. Is this normal?